Quick Answer

A User Requirements Specification (URS) is a controlled document that defines what a cleanroom facility, system, utility, or item of equipment must achieve from the user’s perspective.

For a cleanroom project, the URS may cover intended use, cleanliness classification, environmental conditions, contamination-control requirements, room pressure relationships, materials, capacity, utilities, monitoring, alarms, documentation, training, maintenance, and qualification expectations.

A well-written URS provides the foundation for design, supplier selection, Design Qualification (DQ), Factory Acceptance Testing (FAT), Site Acceptance Testing (SAT), and subsequent IQ, OQ, and PQ activities. It should describe required outcomes using clear and verifiable acceptance criteria without unnecessarily dictating the supplier’s engineering solution.

Key Takeaways

The URS defines what the cleanroom must achieve, not merely what equipment the buyer wants to purchase.
It should be prepared before detailed design and preferably before requesting final supplier quotations.
Requirements must be clear, measurable, traceable, risk-based, and testable.
The project owner or end user remains responsible for approving the URS, even when consultants help prepare it.
A cleanroom URS should address both operational needs and applicable regulatory or quality requirements.
Each critical requirement should eventually be verified through design review, FAT, SAT, commissioning, IQ, OQ, PQ, or another documented activity.
Vague requirements lead to inconsistent quotations, design changes, qualification failures, delays, and commercial disputes.
The URS should remain a controlled reference throughout the system lifecycle.

Introduction

Many cleanroom projects begin with a floor plan, an equipment list, or a request for quotation. However, these documents do not always explain what the finished facility must actually achieve.

For example, a buyer may request “an ISO Class 7 cleanroom” without specifying:

The occupancy state in which the classification must be achieved
The manufacturing process conducted in the room
Temperature and relative-humidity limits
Room pressure relationships
Recovery-time expectations
Required monitoring and alarm functions
Cleaning and disinfection procedures
Personnel and material flows
Applicable GMP or industry requirements
The tests and records required for final acceptance

Suppliers may interpret these missing details differently. Their quotations may therefore appear to describe the same cleanroom while actually covering different technical scopes.

The URS addresses this problem by establishing a documented and approved definition of the user’s needs.

For pharmaceutical projects governed by EU GMP expectations, EU GMP Annex 15 identifies the URS as an early qualification stage. Annex 15 states that specifications for facilities, equipment, utilities, or systems should be defined in a URS and/or functional specification, with essential quality elements built in and GMP risks reduced to an acceptable level.

It also establishes an important principle: the URS should remain a reference throughout the validation lifecycle.

However, not every cleanroom is a pharmaceutical GMP facility. For hospitals, laboratories, electronics manufacturing, food production, medical-device facilities, or other controlled environments, the exact regulatory obligations may differ. Even when a formal GMP URS is not legally required, a structured requirements document remains valuable engineering and procurement practice.

What Is a User Requirements Specification?

A User Requirements Specification is a formal description of the capabilities, conditions, performance, documentation, and compliance outcomes that a user expects from a proposed facility or system.

In a cleanroom project, the subject of a URS could be:

An entire cleanroom facility
A cleanroom HVAC system
A modular operating theatre
An aseptic processing area
A cleanroom envelope
A purified-water or compressed-gas system
A building-management or environmental-monitoring system
A pass box, air shower, FFU system, or other cleanroom equipment
A group of connected systems within one project

The URS establishes the basis against which the design and delivered system will be evaluated.

It answers questions such as:

What will the facility be used for?
Which processes and products must it support?
Which environmental conditions must it maintain?
Which risks must the design control?
Which regulations, standards, and internal procedures apply?
What capacity and operational flexibility are required?
How must the system be cleaned, operated, monitored, and maintained?
What documentation and training must the supplier provide?
How will the owner determine whether the completed system is acceptable?

A URS should focus primarily on required results. It may include mandatory technical constraints where necessary, but it should not become an unstructured collection of preferred products, copied specifications, and supplier catalog descriptions.

Why Is a URS Important for a Cleanroom Project?

Cleanrooms are integrated systems. Their performance depends on the interaction of layout, airflow, filtration, pressure control, envelope integrity, utilities, equipment, operating procedures, personnel behavior, cleaning practices, and monitoring.

A requirement affecting one part of the facility may influence several other systems.

For example, specifying a room pressure differential without defining leakage, door operation, transfer routes, exhaust conditions, and HVAC control philosophy may not produce a stable pressure cascade. Similarly, specifying a cleanliness class without explaining the operating state, process load, occupancy, and contamination sources may lead to an unsuitable airflow design.

A well-prepared URS provides several important benefits.

It aligns the project with the intended use

The design team must understand what activities will take place inside the cleanroom. A sterile pharmaceutical facility, hospital operating room, microbiology laboratory, electronics cleanroom, and food-processing area do not have identical contamination-control requirements.

The URS connects the technical design to actual operations.

It creates a common basis for supplier quotations

Without a controlled set of requirements, suppliers may make different assumptions about:

HVAC scope
Panel and door construction
Filtration stages
Control systems
Monitoring instruments
Qualification tests
Documentation
Installation responsibilities
Utility connections
Training and after-sales services

A clear URS makes commercial and technical comparisons more meaningful. It also strengthens the buyer’s existing cleanroom RFQ by defining the performance and acceptance basis behind the requested scope.

It reduces late design changes

Changes made during conceptual design are usually less disruptive than changes made during fabrication, installation, or qualification.

When operational, quality, maintenance, safety, and regulatory needs are identified early, the design can address them before construction begins. This reduces rework, schedule disruption, and unplanned cost.

It supports qualification and acceptance

The URS provides the starting point for determining what must be verified and when.

A critical requirement may be checked through:

Design review or DQ
Supplier document review
FAT
SAT
Installation inspection
Commissioning
IQ
OQ
PQ
Routine monitoring or periodic requalification

This traceable relationship prevents critical requirements from disappearing between design and handover.

It helps manage project risk

Not every requirement has the same impact. Requirements related to product quality, patient safety, contamination control, operator protection, data integrity, or regulatory compliance normally require greater attention than noncritical preferences.

A risk-based URS helps the project team distinguish between:

Critical quality and compliance requirements
Essential operational requirements
Safety requirements
Engineering and maintenance requirements
Commercial preferences
Desirable but nonessential features

This prioritization supports better design decisions and more efficient qualification.

Is a URS the Same as an RFQ or Technical Specification?

No. These documents are related, but they serve different purposes.

Document	Primary purpose	Main question answered
URS	Defines the user’s needs and required outcomes	What must the facility or system achieve?
RFQ	Invites suppliers to submit a commercial and technical offer	What is the supplier offering, at what price and under what terms?
Functional Specification	Explains how the system will perform its required functions	How will the system operate?
Design Specification	Defines the proposed technical design	How will the requirement be engineered and constructed?
Supplier Proposal	Describes the supplier’s offered solution and exclusions	What solution is included in the quotation?
Validation Plan	Defines the qualification and validation strategy	How will compliance and performance be demonstrated?

The URS may be issued as part of an RFQ package, but an RFQ is not automatically a URS.

A basic RFQ may list room sizes, products, quantities, and requested equipment. A URS goes further by defining the intended use, performance expectations, critical controls, applicable standards, required records, and acceptance principles.

For complex projects, the buyer should prepare or approve the URS before asking suppliers to finalize their technical proposals. This makes it easier to compare offers on an equivalent basis.

Who Should Prepare and Approve the URS?

The project owner or regulated user should own the URS.

A consultant, engineering company, cleanroom contractor, equipment supplier, or validation specialist may help draft the document. However, the end user should not transfer responsibility for defining and approving its operational and quality needs entirely to the supplier.

A multidisciplinary team is normally required.

Depending on the project, contributors may include:

Production or clinical users
Quality assurance
Engineering
Validation
Maintenance
Environmental health and safety
Infection control
Microbiology
Information technology
Procurement
Project management
Regulatory affairs
Cleaning and sanitation personnel

Each function sees different risks.

For example, production may focus on capacity and workflow; quality assurance may focus on compliance and traceability; engineering may evaluate technical feasibility; maintenance may identify service-access requirements; and cleaning personnel may identify inaccessible surfaces or unsuitable finishes.

The approval structure should be defined by the organization’s quality system and project governance. In regulated pharmaceutical projects, appropriate quality oversight should be maintained throughout the qualification lifecycle.

When Should the URS Be Written?

The URS should be developed early—after the intended process and business need are sufficiently understood but before the technical solution becomes fixed.

A typical sequence is:

Define the intended process and project objectives.
Identify users, products, capacity, risks, and regulatory context.
Prepare and approve the URS.
Develop the conceptual design.
Request and evaluate supplier proposals.
Develop functional and detailed design specifications.
Perform Design Qualification.
Fabricate, install, commission, and qualify the system.

In practice, early design studies may be needed to clarify whether certain requirements are feasible. Therefore, URS development is not always a perfectly linear activity. Initial requirements may be refined as process knowledge improves.

However, this refinement must be controlled. Once approved, revisions should have:

A revision number
A documented reason for change
Identification of affected requirements
Appropriate technical and quality review
Formal approval
Assessment of the effect on design, cost, schedule, testing, and qualification

The URS should not be rewritten informally simply to match a supplier’s completed design. If the proposed design cannot meet an approved requirement, the project team should document whether the design must change, the requirement can be justifiably revised, or a formal exception is acceptable.

How Does the URS Fit into the Cleanroom Lifecycle?

The URS is not a document that should be filed away after procurement. It provides continuity from project definition to operation.

Lifecycle stage	How the URS is used
Concept development	Defines intended use, capacity, critical conditions, and project boundaries
Supplier selection	Creates a common basis for evaluating technical proposals
Design development	Guides functional and detailed engineering
DQ	Confirms that the proposed design addresses approved requirements
FAT	Verifies selected requirements before equipment leaves the factory
SAT	Confirms site-specific functions after delivery and assembly
Commissioning	Supports inspection, adjustment, balancing, and functional checks
IQ	Confirms installation against approved requirements and design documents
OQ	Verifies operation across specified ranges and operating modes
PQ	Demonstrates performance under representative operating conditions
Operation	Supports procedures, training, maintenance, monitoring, and change control
Modification	Helps assess whether proposed changes affect intended use or validated status
Decommissioning	Supports controlled retirement, data handling, and system replacement

This lifecycle relationship is one reason the URS must use numbered and traceable requirements.

For example:

URS-HVAC-014: The HVAC control system shall generate a visible and audible alarm when the pressure differential between Room A and Corridor B remains outside the approved operating range for more than the defined delay period.

That requirement can be linked to:

The control-system design
Instrument selection
Alarm logic
DQ review
FAT or software testing
OQ challenge testing
Operating procedures
Calibration and maintenance records

This is much stronger than writing:

The room must have good pressure control.

The second statement cannot be consistently designed, tested, or accepted.

What Is the Difference Between a URS and DQ?

The URS defines the requirements. DQ verifies the suitability of the proposed design against those requirements.

In simple terms:

URS: What does the user need?
DQ: Does the proposed design meet that need?

A DQ should therefore not be performed without an adequately defined design basis. The reviewer needs approved requirements, drawings, specifications, risk assessments, calculations, and supplier information to determine whether the design is suitable for its intended purpose.

If requirements are vague, the DQ may become a superficial document review rather than a meaningful engineering and quality assessment.

This is why the URS should precede DQ and remain connected to the cleanroom commissioning and qualification strategy.

What Should a Cleanroom URS Include?

The exact structure of a URS should reflect the project’s scale, intended use, regulatory environment, and risk level. A small non-GMP cleanroom may require a relatively concise document, while a pharmaceutical facility may need a detailed URS covering multiple systems and hundreds of traceable requirements.

A comprehensive cleanroom URS normally includes the following sections:

Document purpose and scope
Project background
Intended use
Applicable regulations and standards
Process and product information
Capacity and operating schedule
Cleanroom classification
Room layout and zoning
Personnel and material flows
Environmental conditions
HVAC and filtration requirements
Pressure-cascade requirements
Cleanroom envelope and finishes
Doors, windows, and transfer systems
Utilities and process services
Controls, monitoring, and alarms
Cleaning and contamination control
Safety and environmental requirements
Maintenance and serviceability
Documentation and training
Testing, commissioning, and qualification
Project interfaces and supplier responsibilities
Acceptance criteria
Requirement traceability
Change control and approval

Not every section needs the same level of detail. Requirements should be proportionate to their effect on product quality, patient or operator safety, contamination control, compliance, system performance, and business continuity.

How Should the Project Scope Be Defined?

The scope section should establish clear physical, functional, and contractual boundaries.

It should identify:

The facility, department, rooms, or systems covered
New construction, renovation, or expansion status
Processes included in the project
Systems supplied by the cleanroom contractor
Systems supplied by the owner or other contractors
Installation and utility-connection responsibilities
Testing and qualification responsibilities
Work specifically excluded from the contract
Interfaces with existing systems
Phasing or operational restrictions

For example, the scope should clarify whether the supplier is responsible for:

Cleanroom wall and ceiling systems
Doors and windows
HVAC equipment
Ductwork and insulation
Terminal HEPA filter housings
Controls and environmental monitoring
Electrical systems
Medical gases or process gases
Installation labor
Testing, adjusting, and balancing
Cleanroom classification
IQ or OQ documentation
Operator and maintenance training

Unclear scope boundaries are a common cause of missing components and unexpected variation orders.

A statement such as “supply a complete cleanroom” is usually insufficient. Different suppliers may interpret “complete” differently, especially where HVAC equipment, fire protection, utilities, controls, qualification, and building work are divided among multiple contractors.

How Should the Intended Use Be Described?

The intended-use section explains why the cleanroom is needed and what operations it must support.

It should describe:

Products or materials handled
Main manufacturing, clinical, testing, or research activities
Open or closed processing steps
Product exposure conditions
Contamination sensitivity
Hazardous or potent materials
Sterile or nonsterile operations
Personnel numbers
Equipment and process heat loads
Material quantities
Cleaning and disinfection activities
Normal, reduced, and peak operating conditions
Future expansion or process changes, if reasonably foreseeable

The intended use must be sufficiently detailed to guide the engineering design without exposing unnecessary confidential process information.

Consider these two examples:

Weak requirement:

The room shall be suitable for pharmaceutical production.

Improved requirement:

The facility shall support the dispensing and open handling of nonsterile pharmaceutical raw materials under the environmental and contamination-control conditions defined in this URS.

The improved statement gives the design team a clearer understanding of the activity while allowing supporting sections to define containment, classification, pressure, cleaning, and environmental conditions.

How Should Applicable Standards Be Specified?

The URS should identify applicable regulations, standards, guidelines, approved drawings, and internal policies.

Depending on the project, these may include:

ISO 14644 standards
National GMP requirements
EU GMP requirements
WHO GMP guidance
FDA regulations and guidance
Applicable pharmacopoeial requirements
Hospital or healthcare-facility standards
Biosafety requirements
Occupational safety regulations
Fire and building codes
Electrical standards
Local environmental regulations
Client engineering standards
Internal quality procedures

Each reference should be relevant to the facility and jurisdiction. The URS should ideally include the document number, title, revision or edition, and applicable section where practical.

Avoid adding long lists of standards simply to make the document appear comprehensive. Conflicting or irrelevant references create uncertainty rather than control.

The project team should also determine the hierarchy to follow if requirements conflict. Local laws and mandatory regulatory requirements generally take priority, but the hierarchy should be formally reviewed for the individual project.

A useful requirement may state:

The facility shall comply with the applicable regulations and standards listed in Section 4. Where conflicting requirements are identified, the supplier shall notify the owner in writing before finalizing the affected design.

This prevents suppliers from resolving significant conflicts through undocumented assumptions.

How Should Cleanroom Classification Be Defined?

A URS should not state only that a room must be “clean” or “GMP compliant.” It should define the required classification and the conditions under which it applies.

The classification requirement may include:

Required ISO class or GMP grade
Particle sizes considered
Occupancy state
Room name or identification number
Process state
Classification method
Sampling and reporting expectations
Recovery expectations, where applicable
Microbiological conditions, if required separately
Reclassification frequency, if included within the project scope

ISO 14644-1 recognizes occupancy states such as:

As-built: The room is complete and operating, but production equipment, materials, and personnel are not present.
At-rest: Equipment is installed and operating as agreed, but personnel are not performing the process.
Operational: The installation is operating under specified conditions with the stated number of personnel working as intended.

The required state must be identified because a room can meet a classification at rest but fail to maintain it during normal operations.

Weak requirement:

All production rooms shall be ISO Class 7.

Improved requirement:

Room PR-102 shall meet ISO Class 7 airborne particle concentration limits at rest under the operating conditions and test method defined in the approved classification protocol.

If an operational classification is required, the URS should describe or reference representative operating conditions, including occupancy, equipment status, and process simulation.

Cleanroom classification should also be distinguished from continuous or routine monitoring. Classification is a formal demonstration that a cleanroom meets specified particle limits under defined conditions. Monitoring is the ongoing collection and evaluation of data intended to show that the controlled environment remains in an acceptable state.

The distinction is explained further in cleanroom classification vs monitoring.

Should the URS Specify an Air Change Rate?

A URS may specify an air change rate when it is justified by a regulation, approved design standard, process requirement, or established owner specification. However, air changes per hour should not automatically be treated as the primary performance objective.

Cleanroom performance depends on several interacting factors:

Supply-air cleanliness
Airflow pattern
Contaminant generation
Process equipment
Occupancy
Room geometry
Extract and return-air locations
Pressure relationships
Heat and moisture loads
Recovery expectations
Cleaning and operating practices

Two rooms with the same air change rate may perform very differently.

Where appropriate, the URS should define the required outcome—such as particle classification, recovery time, temperature control, pressure stability, or contaminant removal—while allowing the designer to calculate the airflow needed to achieve it.

Overly prescriptive requirement:

The room shall receive exactly 40 air changes per hour.

Performance-based requirement:

The HVAC system shall provide sufficient filtered airflow to maintain the specified cleanliness classification, environmental conditions, pressure relationship, and recovery performance under the defined operating load. The design airflow and supporting calculation shall be submitted for approval.

If a minimum air change rate is mandatory, it should be stated clearly and supported by the applicable requirement or approved design basis.

The method for calculating air changes is covered in the existing cleanroom ACH calculation guide.

How Should Temperature and Relative Humidity Requirements Be Written?

Temperature and relative humidity limits should be based on product, process, personnel, equipment, condensation, static-control,

Part 2

What Should a Cleanroom URS Include?

A cleanroom URS should be detailed enough to guide design, procurement, testing, and qualification, but it should not unnecessarily restrict how qualified suppliers achieve the required results.

The exact structure depends on the facility type, industry, project size, and regulatory environment. A practical URS normally includes the following sections.

1. Document Control and Approval

The document should clearly identify:

Project name and location
Facility, system, or equipment covered
Document number
Revision number
Effective or approval date
Document owner
Authors, reviewers, and approvers
Revision history
Related drawings and reference documents

Document control is especially important because the URS may change as process knowledge develops. Every project participant must know which revision is current.

Superseded versions should be retained according to the organization’s document-control procedure rather than informally deleted or overwritten.

2. Purpose and Scope

The purpose section explains why the URS has been prepared. The scope defines exactly which areas, systems, utilities, interfaces, and services it covers.

A cleanroom URS might include:

Architectural layout
Cleanroom wall and ceiling systems
Floors, coving, doors, and windows
HVAC and air filtration
Pressure-control systems
Environmental monitoring
Electrical and lighting systems
Process utilities
Building-management interfaces
Access control
Fire protection interfaces
Cleanroom furniture and fixed equipment
Testing, commissioning, and qualification
Documentation, training, and after-sales support

The scope should also state important exclusions.

For example, if the cleanroom contractor supplies terminal HEPA filter boxes but not the air-handling units, ductwork, chillers, or building-management system, that boundary must be stated clearly. Otherwise, critical interfaces may remain unassigned.

3. Project Background and Intended Use

The URS should explain what the cleanroom will be used for rather than describing only the rooms and equipment.

Relevant information may include:

Industry and facility type
Product or process
Intended operating activities
Batch or continuous operation
Production capacity
Number of shifts
Expected facility life
Number of operators
Materials and equipment entering the area
Contamination hazards
Cleaning and disinfection methods
Future expansion expectations
Applicable regulatory market

The design requirements for a sterile injectable facility, medical-device assembly room, operating theatre, biosafety laboratory, and electronics cleanroom can be significantly different even when they use similar cleanroom components.

The intended use provides the context needed to interpret every subsequent requirement.

4. Applicable Regulations, Standards, and Guidelines

The URS should identify which requirements apply to the project.

Depending on the facility, these may include:

National building, electrical, mechanical, and fire codes
Occupational health and safety requirements
ISO 14644 cleanroom standards
EU GMP requirements
WHO GMP guidance
FDA regulations or guidance
Applicable pharmacopoeial requirements
Hospital or healthcare facility standards
Biosafety requirements
Internal engineering and quality standards
Customer-specific requirements

References should be specific where possible. Instead of writing “The cleanroom shall comply with all relevant standards,” the URS should identify the applicable document, section, edition, and project interpretation.

However, the project team must be careful when combining standards. Requirements developed for different applications may not be directly interchangeable.

ISO 14644-1 particle classification, for example, does not by itself define:

Microbial limits
Room pressure differentials
Air-change rates
Temperature and humidity
Recovery time
Surface materials
Personnel gowning
Process suitability

The URS must therefore convert the relevant standards and process needs into a coherent set of project-specific requirements.

How Should Individual URS Requirements Be Written?

A good URS requirement should be:

Clear
Necessary
Unambiguous
Technically feasible
Measurable where appropriate
Verifiable
Traceable
Consistent with other requirements
Assigned a unique identifier
Written from the user’s perspective

A practical requirement format is:

[Subject] + shall + [required function or performance] + [defined condition] + [acceptance criterion].

For example:

URS-HVAC-021: The HVAC system shall maintain Room P-101 at 20–24°C during normal occupied operation when the specified process and personnel loads are present.

This is more useful than:

The HVAC system should maintain a comfortable temperature.

“Comfortable” is subjective, while “20–24°C” is measurable. “Should” may also imply a recommendation rather than a mandatory requirement.

Use “Shall” for Mandatory Requirements

Controlled specifications commonly use:

Shall for mandatory requirements
Should for recommendations
May for permitted options
Will for statements of intent or future action

These terms should be defined and used consistently.

Avoid mixing mandatory requirements with preferences unless their priority is clearly identified.

Write One Requirement per Statement

Each numbered requirement should preferably express one testable need.

Poor example:

The room shall be ISO Class 7, operate at positive pressure, have 20 air changes per hour, use H14 filters, maintain 22°C, and be easy to clean.

If any one part fails, it becomes difficult to record the status of the overall requirement.

Better:

URS-ENV-001: The room shall achieve ISO Class 7 particle cleanliness under the specified occupancy state.
URS-ENV-002: The room shall maintain the approved positive-pressure relationship to adjacent areas during normal operation.
URS-ENV-003: The room temperature shall remain within the approved operating range.
URS-ENV-004: Exposed internal finishes shall be compatible with the approved cleaning and disinfection agents.

Separate requirements improve traceability, review, testing, and deviation management.

Avoid Unverifiable Language

The following expressions should normally be avoided unless they are supported by defined acceptance criteria:

High quality
User-friendly
Adequate
Sufficient
Easy to maintain
Best available
Suitable materials
Good sealing
Low noise
Fast recovery
As required
Where necessary
All relevant standards

These phrases communicate an intention but not an objectively verifiable requirement.

For example:

Vague wording	Improved requirement
The room shall have good pressure control.	The room shall maintain the specified differential-pressure range under defined operating conditions.
Doors shall be well sealed.	Closed doors shall support the required room-pressure relationship and meet the approved leakage or sealing criteria.
The system shall recover quickly.	The room shall meet the specified recovery-time acceptance criterion using the approved test method and operating state.
Noise shall be low.	Background sound pressure shall not exceed the defined limit at the specified measurement locations and operating condition.
Surfaces shall be easy to clean.	Exposed surfaces shall be smooth, non-shedding, accessible for cleaning, and resistant to the approved cleaning agents.

Avoid Prematurely Dictating the Design

The URS should normally state what must be achieved while allowing competent designers to propose the most appropriate engineering solution.

Overly prescriptive example:

Each room shall have exactly 25 air changes per hour.

Performance-based alternative:

The HVAC design shall provide sufficient filtered airflow to achieve the specified cleanliness classification, recovery performance, heat-load control, pressure relationship, and process requirements under defined operating conditions.

A fixed ACH may be justified when required by an applicable standard, approved company practice, risk assessment, or known process need. However, ACH should not automatically become a universal design target.

The required airflow depends on factors such as:

Room volume
Cleanliness classification
Contamination generation
Occupancy
Process equipment
Airflow pattern
Filter coverage
Heat load
Exhaust requirements
Pressure cascade
Recovery expectations

The same principle applies to filter grades, room pressures, fan capacity, panel thickness, and other engineering parameters. Prescriptive requirements should have a clear technical, regulatory, operational, or standardization reason.

How Should Cleanroom Classification Requirements Be Defined?

A statement such as “The room shall be ISO Class 7” may be incomplete.

The URS should define:

Applicable classification standard
Required ISO class or GMP grade
Particle sizes to be evaluated
Occupancy or operational state
Room boundaries
Critical zones within the room
Relationship between particle classification and process operation
Required classification documentation
Reclassification expectations where applicable

A better requirement might read:

URS-ENV-011: Processing Room P-101 shall meet ISO Class 7 airborne-particle concentration limits in the approved occupancy state, as defined in the project classification plan and tested according to the applicable edition of ISO 14644-1.

The wording must match the real project requirement. ISO 14644 uses defined occupancy states, including “as-built,” “at-rest,” and “operational.” The URS should not leave the required state open to supplier interpretation.

For a pharmaceutical cleanroom, ISO classification may be only one part of the requirement. The URS may also need to address:

GMP cleanroom grade
Viable environmental monitoring
Contamination-control strategy
Qualification state
Process-specific limits
Alert and action levels
Cleaning and disinfection
Personnel practices

Particle classification alone does not establish that a cleanroom is suitable for a specific manufacturing process.

How Should Temperature and Relative Humidity Be Specified?

Temperature and relative humidity should be based on process, product, personnel, equipment, condensation, static-control, or microbiological considerations.

The URS should define:

Normal operating range
Alert or action limits where applicable
Occupied or unoccupied condition
Measurement location
Seasonal design conditions
Sensor accuracy
Recording requirements
Alarm requirements
Excursion handling
Recovery expectations after door opening or shutdown

Example:

URS-ENV-022: The room shall maintain a temperature of 20–24°C and relative humidity of 40–60% during normal occupied operation under the approved process, equipment, personnel, and outdoor design conditions.

The ranges above are only an example, not a universal cleanroom requirement.

A project should not copy temperature and humidity values from another facility without confirming:

Product sensitivity
Process heat and moisture loads
Operator clothing
Local climate
Condensation risk
Cleaning activities
Equipment limitations
Energy implications

Tight environmental tolerances can substantially increase system complexity, energy use, and cost. They should be justified by actual operational or quality needs.

How Should Room Pressure Requirements Be Written?

Pressure requirements should define the intended containment or protection strategy.

The URS should identify:

Which rooms must be positive or negative
The reference room or adjacent space
Normal operating range
Alarm limits
Alarm delay
Door-open conditions
Shutdown or setback mode
Response to filter loading
Interaction with exhaust systems
Required display and recording
Pressure-monitoring locations
Acceptance-testing conditions

Example:

URS-PRE-006: During normal operation with doors closed, Processing Room P-101 shall maintain the approved positive differential-pressure range relative to Corridor C-101.

A numeric pressure value can be included when it is justified and approved. However, pressure requirements must be coordinated with:

Air supply and exhaust balance
Envelope leakage
Door undercuts and seals
Pass boxes and transfer openings
Door-opening frequency
Interlocks
Local exhaust devices
Fire and smoke-control modes
Temperature effects
HVAC control response

A pressure cascade shown on a drawing is not sufficient if the physical systems cannot consistently maintain it.

The project team should review cleanroom differential pressure as part of the complete contamination-control strategy rather than treating each room pressure as an isolated value.

What HVAC Requirements Should Be Included?

HVAC requirements should describe expected performance, capacity, operating modes, controls, monitoring, maintainability, and critical interfaces.

The URS may need to address:

Air cleanliness and filtration

Required particle classification
Filtration stages
Terminal filtration expectations
Filter efficiency or classification
Filter installation arrangement
Scan-test access
Differential-pressure monitoring
Filter replacement access
Required certificates
Leakage-test expectations

If terminal HEPA filters must be integrity tested, the design should provide safe and practical access for aerosol introduction, scanning, measurement, and filter replacement. The acceptance strategy can be coordinated with the existing HEPA filter integrity testing requirements.

Airflow performance

Required airflow pattern
Supply and return arrangement
Minimum or design airflow
Air velocity where relevant
Recovery-time target
Airflow visualization requirements
Critical-zone protection
Turbulence and obstruction considerations

Operating modes

The URS should define expected modes such as:

Normal occupied operation
Unoccupied or setback mode
Cleaning mode
Maintenance mode
Emergency mode
Shutdown
Restart
Decontamination mode where applicable

For each mode, it may be necessary to define which parameters remain controlled and how transitions occur.

Capacity and design conditions

The design basis should identify:

Maximum personnel occupancy
Process-equipment heat loads
Lighting loads
Product or material loads
Outdoor design conditions
Exhaust volumes
Door-opening frequency
Simultaneous room operation
Future capacity allowance

Unstated loads are a common cause of systems failing to maintain temperature, humidity, or pressure after operations begin.

Controls and alarms

The URS may define requirements for:

Temperature control
Humidity control
Airflow control
Pressure control
Fan status
Filter differential pressure
Alarm generation
Alarm delays
Setpoint security
Data recording
Audit trails where required
User-access levels
Communication with BMS or EMS
Sensor calibration
Power-loss response
Restart behavior

The user should distinguish between parameters that require continuous control, continuous monitoring, periodic measurement, local indication, central recording, or alarm notification.

What Cleanroom Envelope Requirements Should Be Included?

The cleanroom envelope includes walls, ceilings, floors, coving, penetrations, doors, windows, and interfaces with services.

The URS should address performance rather than appearance alone.

Wall and ceiling systems

Requirements may include:

Surface finish
Smoothness
Cleanability
Resistance to disinfectants and cleaning chemicals
Shedding characteristics
Joint construction
Sealant compatibility
Panel core material
Fire performance
Impact resistance
Load-bearing requirements
Ceiling access
Walkable ceiling requirements
Integration with lights, filters, sprinklers, and utilities
Repair and replacement
Color and visual finish

The panel core should be selected according to fire, structural, thermal, acoustic, moisture, hygiene, and project requirements—not solely by price.

Floors and coving

Requirements may include:

Seamless or welded construction
Chemical resistance
Slip resistance
Static-control properties
Load capacity
Drainage
Floor-to-wall coving
Cleaning compatibility
Crack and joint treatment
Hygienic detailing around penetrations

A requirement for floor drains should be evaluated carefully. Drains can be necessary for some wet processes but undesirable in other controlled environments.

Doors

Door requirements may cover:

Clear opening size
Opening direction
Manual or automatic operation
Hermetic or cleanroom sealing performance
Surface material
Vision panels
Flush construction
Interlocks
Access control
Emergency release
Fire rating
Hardware
Kick plates or impact protection
Cleaning resistance
Pressure compatibility
Operating force
Safety sensors
Power-failure behavior

Door selection must be coordinated with room pressure, personnel and material flow, trolley dimensions, fire strategy, emergency escape, and daily operating frequency.

Windows

The URS may specify:

Flush glazing
Double-glazed construction
Frame material
Sealed cavity
Condensation resistance
Fire rating
Radiation protection where applicable
Privacy blinds
Observation requirements
Cleaning accessibility

Penetrations and interfaces

Every penetration through the cleanroom envelope can affect cleanability, leakage, pressure stability, fire performance, and pest control.

The URS should require appropriate sealing and hygienic integration for:

Ducts
Pipes
Electrical conduits
Cable trays
Gas terminals
Sprinklers
Lights
Filters
Monitoring sensors
Process equipment
Wall-mounted furniture

Responsibility for completing and inspecting these seals should be clearly assigned.

How Should Personnel and Material Flow Requirements Be Defined?

The URS should describe how people, materials, waste, equipment, and products move through the facility.

Relevant requirements may include:

Personnel entry and exit sequence
Gowning stages
Material entry and exit
Waste-removal route
Clean and dirty separation
Airlocks
Pass boxes
Decontamination steps
Equipment-transfer routes
Emergency egress
Prevention of cross-flow
Door interlocks
Occupancy limits
Change-room storage
Cleaning-tool movement

Flow requirements should be based on the real process sequence and contamination risks, not added after the room layout has already been fixed.

The project team should consider:

Whether incoming and outgoing materials use the same route
How rejected or contaminated materials are removed
Whether personnel paths cross material paths
How doors affect the pressure cascade
Whether carts can turn and pass through openings
How maintenance personnel access technical systems
How large equipment will be installed or replaced
How emergency evacuation affects controlled routes

A technically compliant room can still operate poorly if the movement strategy is impractical.

How Should Pass Boxes, Airlocks, and Transfer Systems Be Specified?

A transfer system should be selected according to contamination risk, transfer frequency, material size, pressure relationships, and required treatment.

The URS may include:

Internal chamber dimensions
Load capacity
Door opening direction
Interlocking
Door-status indication
Surface finish
Corner radius
Cleaning access
Pressure relationship
Ventilation and filtration
UV or other treatment where justified
Decontamination cycle
Cycle status and alarms
Emergency release
Power-failure behavior
Data recording
Qualification requirements

The user should not specify a dynamic pass box simply because it appears more advanced. A transfer device must match the intended contamination-control function.

For example, the team should determine whether the transfer system is intended to:

Maintain physical separation
Protect cleaner areas from adjacent environments
Remove surface contamination
Support a pressure cascade
Provide filtered purging
Support chemical or biological decontamination
Contain hazardous materials

These functions require different designs and acceptance tests.

What Monitoring and Data Requirements Should Be Included?

Monitoring requirements should be derived from process risk, facility type, applicable regulations, and the control strategy.

Parameters may include:

Room differential pressure
Temperature
Relative humidity
Nonviable airborne particles
Viable environmental monitoring
Air velocity
Airflow
Filter differential pressure
Door status
Equipment status
Alarm status
Utility conditions

The URS should clarify:

What is monitored
Where sensors are located
Whether monitoring is continuous or periodic
Required measurement range and accuracy
Data-recording interval
Alarm and action thresholds
Alarm delays
Data retention
Trending
User access
Time synchronization
Backup and restoration
Audit trails where applicable
Interface with other systems
Calibration requirements
Report generation

The distinction between classification and routine monitoring is important. Classification demonstrates that a cleanroom meets defined particle limits under specified conditions. Routine monitoring provides ongoing information about the controlled environment and helps detect loss of control.

These activities have different objectives and should not be treated as interchangeable.

How Should Safety and Maintenance Requirements Be Addressed?

A cleanroom must be maintainable without creating unnecessary contamination, safety, or operational risks.

Maintenance requirements may include:

Access to filters, fans, sensors, dampers, lights, and controls
Access from technical areas where practicable
Safe filter replacement
Isolation and lockout provisions
Calibration access
Spare-parts requirements
Consumable lists
Recommended preventive-maintenance intervals
Diagnostic functions
Lifting and handling provisions
Replacement route for major equipment
Required maintenance tools
Technical training
Service manuals
Local service support

Safety requirements may cover:

Fire performance
Emergency exits
Emergency door release
Electrical safety
Machinery guarding
Chemical exposure
Biological hazards
Radiation protection
Pressure-related hazards
Noise
Ergonomics
Safe access above ceilings
Emergency power
Alarm annunciation
Applicable occupational safety requirements

Maintenance should be considered during design. A filter that passes its initial test but cannot be safely accessed, scanned, or replaced represents a lifecycle problem.

What Documentation Requirements Should Be Included in a URS?

Documentation should be treated as part of the deliverable, not as an optional administrative addition after installation.

A technically acceptable cleanroom can still face delayed handover if drawings, certificates, test records, operating manuals, or qualification documents are incomplete.

The URS should specify:

Required document list
Document format
Required language
Electronic and hard-copy requirements
Review and approval stages
Submission schedule
Document numbering
Revision control
Final as-built records
Retention requirements
Responsibility for preparing and approving each document

Depending on the project scope, supplier documentation may include:

Technical proposal
Design basis
Room data sheets
Equipment data sheets
Material submittals
General arrangement drawings
Cleanroom layout drawings
Personnel and material-flow drawings
Pressure-cascade diagrams
HVAC schematics
Airflow calculations
Heat-load calculations
Ductwork drawings
Electrical drawings
Control-system architecture
Instrument list
Alarm matrix
Input/output list
Panel and door details
Utility requirements
Material certificates
Filter certificates
Calibration certificates
Welding or installation records where applicable
Inspection and test plans
FAT and SAT protocols
Commissioning procedures and records
IQ and OQ documentation
Cleaning procedures
Operation and maintenance manuals
Recommended spare-parts list
Training materials
Final as-built drawings

Each document should have a defined purpose and expected level of detail.

For example, requesting an “HVAC report” is less effective than specifying that the supplier must provide airflow calculations, design assumptions, room-by-room supply and return volumes, pressure-balance information, equipment selection data, and final testing and balancing results.

What Training Requirements Should the URS Define?

Training should be appropriate to the systems being delivered and the responsibilities of the personnel receiving it.

The URS may require training for:

Operators
Maintenance technicians
Engineering personnel
Quality personnel
Environmental-monitoring personnel
System administrators
Cleaning personnel
Validation personnel

Training topics may include:

Normal operation
Startup and shutdown
Operating modes
Alarm response
Emergency procedures
Cleaning and disinfection
Filter inspection and replacement
Calibration
Preventive maintenance
Troubleshooting
Access control
Data review and reporting
Change control
Backup and restoration
Safe maintenance access

The URS should define the expected:

Training language
Training location
Number of sessions
Number of participants
Instructor qualifications
Training materials
Practical demonstrations
Competency checks
Attendance records
Completion certificates
Refresher training where required

A signature on an attendance sheet alone does not demonstrate that personnel can safely and correctly operate a complex system. For critical functions, practical demonstration or documented competency assessment may be appropriate.

What Spare Parts and After-Sales Requirements Should Be Included?

Cleanroom operation can be disrupted when critical consumables or replacement components are unavailable.

The URS should therefore identify requirements for:

Commissioning spare parts
Initial operating spares
Critical replacement parts
Recommended consumables
Special tools
Locally available components
Manufacturer and model information
Expected service life
Storage conditions
Shelf life
Replacement procedures
Warranty support
Technical-response time
Remote support
On-site service
Long-term component availability

The supplier may be required to provide a categorized spare-parts list showing:

Part number
Description
Equipment reference
Manufacturer
Recommended quantity
Replacement frequency
Lead time
Criticality
Unit price

Standardized and locally available components can reduce operational risk, but they should not be selected without considering performance, compatibility, calibration, cleanability, and regulatory requirements.

How Should FAT Requirements Be Connected to the URS?

Factory Acceptance Testing verifies selected requirements before equipment or modular assemblies are shipped.

Not every URS requirement can be verified at the factory. Site-dependent requirements—such as final room pressure, installed airflow balance, or integration with the building-management system—may only be testable after installation.

However, FAT may be suitable for checking:

Dimensions
Materials and finishes
Fabrication quality
Component identity
Control-panel construction
Input/output functions
Alarm logic
Door interlocks
Access-control functions
Pass-box operation
Software screens
Operating modes
Safety devices
Documentation
Instrument certificates
Equipment labels
Packaging readiness

The URS should not merely state, “FAT shall be performed.” It should define or reference:

Equipment subject to FAT
Applicable requirements
Test responsibilities
Protocol approval
Witnessing requirements
Test instruments
Acceptance criteria
Deviation handling
Retesting
FAT report
Release for shipment

A requirements traceability matrix can identify which URS items will be verified during Factory Acceptance Testing and which must remain open until site testing.

Passing FAT does not automatically mean the complete cleanroom has been accepted. It confirms only the defined scope tested under factory conditions.

How Should SAT and Commissioning Requirements Be Defined?

SAT verifies selected functions after delivery, installation, and connection at the project site.

It may confirm:

Equipment identity
Shipping condition
Correct assembly
Utility connections
Site interfaces
Control integration
Local and remote operation
Alarm transmission
Interlocks
Communication networks
Safety functions
Site-specific operating conditions

The SAT scope should account for anything that could change during:

Transportation
Storage
Installation
Reassembly
Utility connection
Software configuration
Integration with other systems

Commissioning is broader than a single acceptance test. It involves inspecting, starting, adjusting, balancing, troubleshooting, and documenting systems so that they are ready for formal qualification or operational handover.

Cleanroom commissioning activities may include:

Installation inspections
Ductwork inspection
Pressure testing
Air leakage testing
Flushing and cleaning
Electrical checks
Instrument calibration
Fan startup
Airflow balancing
Room pressure adjustment
Temperature and humidity tuning
Control-loop adjustment
Alarm testing
Filter installation checks
Preliminary HEPA integrity testing
Airflow visualization
Functional performance testing
Punch-list management

The URS should define the owner’s expected commissioning records and readiness criteria.

Qualification should not be forced to compensate for incomplete commissioning. If systems are still unstable, incorrectly balanced, or subject to unresolved construction defects, formal qualification results may be unreliable.

How Should IQ, OQ, and PQ Requirements Be Connected to the URS?

IQ, OQ, and PQ provide documented evidence that the installed systems meet defined design, operational, and performance expectations.

Installation Qualification

IQ typically confirms that the installed facility or system:

Matches approved drawings and specifications
Uses the approved components and materials
Has been installed correctly
Has required identification and labeling
Has appropriate utility connections
Includes required documentation
Has calibrated instruments
Has completed installation records
Meets applicable installation requirements

Operational Qualification

OQ typically verifies that the installed system operates as intended across specified conditions and ranges.

OQ may include:

Operating modes
Control functions
Alarm challenges
Interlocks
Setpoint control
Failure responses
Power-loss behavior
Differential-pressure control
Temperature and humidity control
Airflow performance
HEPA filter integrity
Recovery testing
Airflow visualization
Classification testing under the defined state

Performance Qualification

PQ demonstrates that the integrated system performs effectively and reproducibly under representative operating conditions.

Depending on the project, PQ may consider:

Normal personnel occupancy
Process equipment operation
Material movement
Cleaning activities
Routine door opening
Environmental conditions
Microbiological monitoring
Product or process performance
Multiple operating cycles
Representative worst-case conditions

A URS requirement should be assigned to the most appropriate verification stage. Repeating every test in FAT, SAT, IQ, OQ, and PQ is not necessarily efficient or scientifically justified.

The objective is adequate, risk-based verification—not maximum document volume.

What Is a Requirements Traceability Matrix?

A Requirements Traceability Matrix, commonly called an RTM, connects each URS requirement to the documents, design features, and tests used to satisfy and verify it.

A simplified matrix may include:

URS ID	Requirement summary	Criticality	Design reference	Verification stage	Test reference	Status
URS-ENV-001	ISO classification	Critical	HVAC Design Spec 4.2	OQ	OQ-ENV-001	Open
URS-PRE-006	Room pressure relationship	Critical	Pressure Diagram P-01	OQ/PQ	OQ-PRE-004	Open
URS-DOR-012	Door interlock	Major	Door Control Spec 3.1	FAT/SAT/OQ	FAT-INT-002	Passed
URS-DOC-005	As-built drawings	Major	Document Register	Handover	DOC-CHK-005	Open
URS-TRN-003	Maintenance training	Major	Training Plan	Handover	TRN-REC-003	Planned

A well-maintained RTM helps the team answer:

Has every URS requirement been addressed by the design?
Where is the approved design solution documented?
Which requirements are critical?
How will each requirement be verified?
Which tests have been completed?
Are any requirements still open?
Have design changes affected previous tests?
Is objective evidence available?

The RTM should be started early and updated throughout the project. Creating it only at the end often reveals missing evidence when correction is expensive or disruptive.

How Should URS Requirements Be Prioritized?

Not all requirements require the same level of control or verification.

A project may categorize requirements as:

Critical
Major
Minor
Mandatory
Desirable
Quality-critical
Safety-critical
Business-critical
Noncritical engineering preference

The exact terminology should be defined by the organization.

Criticality should be based on documented risk rather than personal preference. Factors may include potential impact on:

Product quality
Patient safety
Operator safety
Contamination control
Cross-contamination
Process performance
Data integrity
Regulatory compliance
Facility availability
Business continuity

For example, a room-pressure alarm protecting against cross-contamination may be critical, while a preferred touchscreen color may be noncritical.

Prioritization helps:

Focus design reviews
Determine supplier obligations
Define qualification depth
Allocate project resources
Evaluate deviations
Make informed commercial decisions

However, labeling a requirement as “noncritical” does not mean it can be ignored. It remains a contractual or project requirement unless formally changed.

What Is the Role of Quality Risk Management?

Quality Risk Management helps determine:

Which requirements are necessary
Which functions are critical
Where controls are required
How much design review is appropriate
Which requirements must be tested
What test depth is justified
Which failures require escalation
Whether a proposed deviation is acceptable
When requalification may be necessary

Potential tools include:

Risk ranking
Process hazard analysis
Failure Mode and Effects Analysis
Hazard Analysis and Critical Control Points
Cause-and-effect analysis
Contamination-control risk assessment

The selected method should match the complexity and risk of the project.

Risk management should not be used to justify omitting necessary controls merely because they are costly or inconvenient. The process should be scientifically sound, documented, and reviewed by appropriate functions.

How Should Changes to the URS Be Controlled?

Requirements often evolve as the project develops. Change itself is not necessarily a failure, but uncontrolled change creates substantial risk.

A URS change-control process should address:

What requirement is changing?
Why is the change necessary?
Who requested it?
Does it affect intended use?
Does it affect product quality, safety, or compliance?
Which drawings and specifications are affected?
Does it affect supplier scope or price?
Does it affect the schedule?
Must risk assessments be updated?
Must completed tests be repeated?
Does the RTM need revision?
Who must review and approve the change?

For example, changing a cleanroom door from a standard cleanroom door to a hermetic automatic door may affect:

Wall reinforcement
Electrical supply
Access control
Pressure leakage
Emergency release
Fire strategy
Controls
Cleaning
Maintenance
FAT and SAT
Spare parts
Project cost

A seemingly isolated product change may therefore require multidisciplinary assessment.

What Happens When a Supplier Cannot Meet a URS Requirement?

The supplier should identify the deviation clearly rather than silently changing or omitting the requirement.

A deviation response should include:

URS requirement number
Exact requirement
Supplier’s proposed solution
Nature of the deviation
Technical justification
Risk or performance impact
Regulatory impact
Cost impact
Schedule impact
Alternative options
Required owner decision

The project team can then:

Accept the proposed solution
Request a revised design
Modify the requirement through formal change control
Accept the deviation with conditions
Reject the proposal

Suppliers should be encouraged to provide a compliance matrix with their quotation. A typical response format is:

Comply
Partially comply
Do not comply
Not applicable
Clarification required

“Comply” should mean full compliance without hidden exclusions. Any qualification, assumption, or alternative should be explained.

Should a URS Include Specific Brands or Manufacturers?

Brand-specific requirements may be appropriate when there is a justified need, such as:

Compatibility with existing systems
Site-wide standardization
Validated replacement policy
Local maintenance capability
Spare-parts availability
Cybersecurity approval
Regulatory or customer requirements

However, specifying brands without technical justification can:

Restrict competition
Increase cost
Reduce engineering flexibility
Create supply-chain dependence
Encourage substitution disputes
Exclude technically equivalent solutions

Where possible, the URS should define performance, material, interface, compliance, serviceability, and documentation requirements.

If equivalent alternatives are permitted, the approval process should be stated clearly.

What Acceptance Criteria Should Be Included?

Acceptance criteria define the conditions under which a requirement is considered satisfied.

Good acceptance criteria should be:

Objective
Measurable where appropriate
Related to the intended use
Supported by an approved method
Achievable under defined conditions
Consistent with applicable standards
Agreed before testing

Acceptance criteria may address:

Dimensions
Materials
Particle concentration
Airflow
Air velocity
Differential pressure
Temperature
Relative humidity
Recovery time
Leakage
Filter integrity
Sound level
Illumination
Alarm response
Interlocks
Data recording
Documentation completeness
Training completion

The requirement should also define the test condition where the result could otherwise be misleading.

For example:

Doors open or closed
HVAC in normal or setback mode
Room as-built, at-rest, or operational
Maximum or typical occupancy
Process equipment operating or stopped
Normal or worst-case outdoor condition
Clean or loaded filters
Normal power or emergency power

A numeric limit without a defined test condition may not provide a fair or reproducible basis for acceptance.

How Should Deviations and Failed Tests Be Managed?

A failed test should not be erased, informally repeated, or replaced with a passing result without explanation.

The deviation process should document:

What happened
Which requirement or acceptance criterion was affected
Immediate actions
Investigation
Root cause where appropriate
Impact assessment
Corrective action
Retest requirements
Final disposition
Required approvals

A retest should occur only after the reason for failure has been understood and appropriate action taken.

If a result is accepted despite not meeting the original criterion, the decision should be supported by:

Documented technical justification
Risk assessment
Regulatory assessment where applicable
Formal approval
URS or design change where required
Updated traceability documentation

Unresolved deviations should be evaluated before proceeding to the next qualification stage.

What Are the Most Common URS Mistakes?

Copying another project’s URS without adaptation

A previous URS can provide a useful structure, but its room classifications, products, processes, environmental limits, regulations, and operating assumptions may not apply to the new project.

Copied requirements can create unnecessary cost or leave important risks unaddressed.

Writing the URS after supplier selection

When the URS is written after the solution has already been purchased, it may simply describe the selected equipment instead of independently defining user needs.

This weakens procurement comparison and DQ.

Treating the supplier proposal as the URS

A supplier proposal describes what the supplier offers. It does not necessarily capture every operational, quality, maintenance, safety, and regulatory need of the user.

Using vague statements

Requirements such as “high quality,” “easy to use,” or “GMP compliant” are difficult to verify unless translated into specific acceptance criteria.

Overengineering the requirements

Unnecessarily narrow temperature, humidity, pressure, filtration, material, or redundancy requirements can significantly increase capital and operating costs.

Every demanding requirement should have a clear reason.

Specifying products without defining performance

A detailed equipment list does not replace requirements for integrated facility performance.

Ignoring interfaces

Many failures occur between systems rather than within individual components. Typical examples include:

Door and access-control interfaces
HVAC and envelope leakage
Pass boxes and room pressure
Sensors and BMS
Lights and ceiling panels
Utilities and process equipment
Fire alarms and door release
Emergency power and controls

Failing to define verification

A requirement without an identified verification method may remain untested until handover—or never be tested at all.

Failing to involve end users

A technically elegant facility may still be difficult to operate, clean, maintain, or qualify if the relevant users were not involved.

Allowing uncontrolled changes

Informal changes through email, messaging applications, verbal instructions, or marked-up drawings can cause different teams to work from different requirements.

How Can International Buyers Improve Supplier Comparisons?

International cleanroom projects often involve differences in terminology, standards, local codes, documentation practices, and scope assumptions.

Buyers can improve comparison by issuing:

Approved URS
Room data sheets
Room list
Layout drawings
Personnel and material-flow diagrams
Pressure-cascade requirements
Equipment and utility lists
Applicable standards
Supplier-scope matrix
Documentation requirements
Testing and qualification expectations
Commercial terms
Required compliance matrix

Suppliers should be asked to identify:

Included scope
Excluded scope
Assumptions
Deviations
Optional items
Local responsibilities
Utility requirements
Civil-work requirements
Testing scope
Travel and accommodation assumptions
Installation supervision
Training
Warranty
Lead time

A low quotation may reflect a narrower scope rather than a more competitive price. The URS and compliance matrix help expose these differences before contract award.

How Detailed Should a Cleanroom URS Be?

The correct level of detail depends on project risk and complexity.

A small nonregulated controlled room may require a relatively concise URS. A sterile pharmaceutical facility, complex laboratory, or integrated modular operating department may require a much more extensive document.

The URS should be detailed enough that:

The design team understands the intended use.
Suppliers can prepare comparable proposals.
Critical requirements are not left to assumption.
Acceptance criteria can be developed.
DQ can meaningfully evaluate the design.
Qualification activities can be planned.
Commercial scope is sufficiently clear.
Changes can be assessed against an approved baseline.

It should not be so prescriptive that it:

Prevents reasonable engineering solutions
Copies an unverified design
Creates contradictions
Adds unnecessary cost
Confuses preferences with critical requirements
Becomes impossible to maintain

The goal is controlled clarity, not document length.

Buyer’s Checklist: What Should You Confirm Before Approving a Cleanroom URS?

Before approving the URS, confirm that:

The intended use and process are clearly defined.
The scope and exclusions are unambiguous.
System interfaces and responsible parties are identified.
Applicable regulations and standards are listed accurately.
Required cleanroom classification and occupancy state are defined.
Temperature and relative-humidity requirements are justified.
Room pressure relationships and containment objectives are clear.
Personnel, material, waste, and equipment flows have been reviewed.
Maximum occupancy and process loads are defined.
HVAC operating modes are described.
Filtration and filter-testing requirements are included.
Envelope, doors, windows, floors, and penetrations are addressed.
Cleaning and disinfection requirements are defined.
Monitoring, alarms, data, and calibration requirements are included.
Utility requirements and connection boundaries are clear.
Safety and emergency functions are included.
Maintenance access and replacement routes have been considered.
Required supplier documents are listed.
FAT, SAT, commissioning, IQ, OQ, and PQ expectations are defined.
Training, spare parts, warranty, and support requirements are included.
Each requirement has a unique identifier.
Critical requirements are identified through risk assessment.
Requirements are measurable or otherwise verifiable.
Vague or contradictory language has been removed.
A requirements traceability strategy has been established.
All relevant user, engineering, quality, and safety functions have reviewed the document.
The URS has been formally approved and placed under change control.

Common Misconceptions About the URS

“The URS is just an equipment list.”

An equipment list identifies what may need to be purchased. A URS defines what the facility or system must achieve, how it will be used, which constraints apply, and how acceptance will be determined.

“The cleanroom supplier should write and approve the URS.”

A supplier or consultant can assist with drafting, but the project owner must define and approve its own needs. Otherwise, the requirements may be shaped primarily around the supplier’s standard solution.

“ISO Class 7 is a complete cleanroom specification.”

ISO classification defines permitted airborne-particle concentrations under specified conditions. It does not by itself define the complete contamination-control, operational, environmental, material, monitoring, or qualification strategy.

“More detail always produces a better URS.”

More relevant and verifiable detail improves clarity. Excessive, copied, contradictory, or unjustified detail can make the document harder to use and unnecessarily restrict the design.

“Once the contract is awarded, the URS is no longer needed.”

The URS remains a reference for DQ, FAT, SAT, commissioning, IQ, OQ, PQ, change control, and lifecycle management.

“Every URS requirement must be tested during OQ.”

Requirements should be verified at the most appropriate lifecycle stage. Some are confirmed through design review, document review, inspection, FAT, SAT, IQ, OQ, PQ, or operational records.

Expert Tip

Create the requirements traceability matrix while writing the URS—not after construction.

For every critical requirement, ask three questions:

Where will the design solution be documented?
At which lifecycle stage will the requirement be verified?
What objective evidence will demonstrate acceptance?

If the project team cannot answer these questions, the requirement is probably too vague, incomplete, or disconnected from the qualification strategy.