Cleanroom Systems
Modular Cleanrooms, Airflow, Pressure, FFUs & Returns
Cleanroom performance depends on filtered supply air, pressure strategy, return placement, particle control, room hierarchy, and verification. A room can look clean but still fail if airflow direction, returns, pressure or documentation are wrong.
How Cleanroom Air Recirculates
Clean air is supplied through FFUs or HEPA modules, moves down through the work zone, pushes particles toward return grilles, then recirculates back through filtration. The repeated cycle helps reduce particle concentration and keeps the room closer to the required ISO class.
Supply Air
FFUs deliver filtered air into the clean zone through HEPA or ULPA media depending on room requirements.
Particle Capture
Airflow carries particles away from the critical work zone so they can return to filtration instead of settling.
Returns
Low wall or side returns help guide air movement and reduce dead zones when the layout is designed correctly.
| Airflow Component | What It Does | Why It Matters | Common Failure |
|---|---|---|---|
| FFU / HEPA Supply | Introduces filtered air into the controlled space. | Particle control starts with clean supply air and enough air movement through the work zone. | Too few FFUs, blocked airflow, poor filter maintenance or unbalanced supply. |
| Work Zone | The critical area where personnel, equipment and product interact. | This is where particle control matters most. | Dead zones, turbulence around equipment or personnel standing in critical airflow. |
| Low Wall Returns | Pulls air out of the room low on the walls and guides the return path. | Good return placement reduces stagnation and helps move particles away from the work zone. | Returns placed too high, blocked by equipment or not balanced with supply airflow. |
| Recirculation Path | Moves air back through filtration or mechanical systems. | Repeated filtration helps reduce particle concentration over time. | Short-circuiting, poor return strategy or recirculation that bypasses critical zones. |
Cleanroom design is not only about adding more filters. FFU quantity, return placement, pressure strategy, room layout, equipment location and verification all need to work together.
ISO 14644 Cleanroom Classifications
ISO classes are based on airborne particle concentration per cubic meter.
ISO 14644-1 classifies cleanrooms and controlled environments by the maximum concentration of airborne particles at specific particle sizes. Lower ISO numbers mean stricter particle limits and cleaner environments.
| ISO Class | ≥0.1 µm / m³ | ≥0.2 µm / m³ | ≥0.3 µm / m³ | ≥0.5 µm / m³ | ≥1.0 µm / m³ | ≥5.0 µm / m³ | Approx. ≥0.5 µm / ft³ | Common Use |
|---|---|---|---|---|---|---|---|---|
| ISO 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | — | ≈100 | ISO 5 PECs, laminar flow work zones, sterile critical areas, very sensitive manufacturing. |
| ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 | ≈1,000 | High-control medical device, electronics, aerospace or precision assembly environments. |
| ISO 7 | — | — | — | 352,000 | 83,200 | 2,930 | ≈10,000 | Sterile buffer rooms, medical device cleanrooms, electronics and controlled manufacturing. |
| ISO 8 | — | — | — | 3,520,000 | 832,000 | 29,300 | ≈100,000 | Ante-rooms, gowning, packaging, material transfer and general controlled environments. |
| ISO 9 | — | — | — | 35,200,000 | 8,320,000 | 293,000 | ≈1,000,000 | Room air reference or lightly controlled spaces. |
The standard classification is expressed per cubic meter. The approximate particles per cubic foot column is included only as a practical reference for clients familiar with legacy Federal Standard 209E language such as Class 100, Class 10,000 and Class 100,000.
ISO 5
Used for the most critical areas, usually within primary engineering controls or very controlled work zones.
ISO 7
Common for sterile buffer rooms, medical device manufacturing, precision assembly and controlled production spaces.
ISO 8
Common for ante-rooms, gowning areas, packaging, material transition spaces and lower-risk support areas.
Class Selection
The correct ISO class depends on product risk, process sensitivity, regulatory requirements, personnel flow, equipment and verification needs.
USP Compounding Environments
USP 795, USP 797 and USP 800 require different facility strategies.
USP chapters are not the same as ISO particle classifications. ISO defines air cleanliness classes. USP chapters define compounding standards, facility expectations, environmental controls, personnel practices and documentation requirements for different types of pharmacy compounding.
| USP Chapter | Compounding Type | Typical Space Type | ISO Classification | Pressure Strategy | Airflow / Exhaust | What Happens There | VIMO Design Focus |
|---|---|---|---|---|---|---|---|
| USP 795 | Nonsterile compounding preparations. | Designated nonsterile compounding area; may involve powder handling or containment depending on ingredients. | Not generally an ISO-classified cleanroom requirement by itself. | Usually neutral or facility-dependent. If hazardous drugs are involved, USP 800 containment may apply. | Process-dependent ventilation, dust control, cleanable surfaces and workflow separation. | Creams, gels, ointments, oral liquids, capsules, topical preparations and other CNSPs. | Cleanable finishes, workflow, containment awareness, powder control, flooring and coordination with USP 800 if hazardous. |
| USP 797 | Sterile compounding preparations. | PEC, buffer room, ante-room and sterile compounding suite. | Typically ISO 5 PEC supported by ISO 7 buffer room and ISO 8 or classified ante-room depending on configuration. | Positive pressure for non-hazardous sterile compounding areas. | HEPA-filtered air, room hierarchy, pressure control, environmental monitoring and documented cleaning. | Sterile preparations where patient safety depends on contamination control. | ISO hierarchy, FFUs/HEPA modules, returns, pressure, cleanable finishes, layout and certification readiness. |
| USP 800 | Hazardous drug handling. | Hazardous drug storage, nonsterile HD compounding room, sterile HD buffer room or containment suite. | Depends on sterile vs nonsterile hazardous process. Sterile HD compounding uses ISO-classified spaces; nonsterile HD may not require ISO classification but still requires containment. | Negative pressure relative to adjacent areas for containment. | Externally vented exhaust strategy is commonly required; many HD spaces reference minimum 12 ACPH, while sterile HD buffer rooms commonly require higher airflow to meet ISO class. | Receiving, storing, compounding or handling hazardous drugs where residue, vapor or particles must be contained. | Negative pressure, exhaust coordination, return/exhaust placement, containment workflow and worker protection. |
Practical warning: USP 795, USP 797 and USP 800 can overlap. A nonsterile compounding room under USP 795 may also need USP 800 containment if hazardous drugs are involved. A sterile hazardous room may need both USP 797 sterile controls and USP 800 negative-pressure containment.
Positive vs Negative Pressure
Pressure strategy decides which direction air moves when doors open, seams leak, or people move between spaces. Positive pressure protects the room from outside contamination. Negative pressure contains hazardous contaminants inside the room.
Positive Pressure
Used when the goal is to keep outside particles from entering the controlled space.
- Used in sterile compounding, electronics, medical devices, and clean manufacturing.
- Protects product, process, and sensitive components.
Negative Pressure
Used when the goal is to prevent hazardous residue, vapors, or particles from escaping.
- Used for USP 800 hazardous drug handling and containment environments.
- Protects workers, adjacent rooms, and the surrounding facility.
| Pressure Strategy | Air Direction | Protects | Common Applications | Typical Design Concern |
|---|---|---|---|---|
| Positive Pressure | Air leaves the room through leakage paths. | Product, process and clean zone. | USP 797 non-hazardous sterile compounding, medical device, electronics, clean manufacturing. | Prevent outside contamination from entering. |
| Negative Pressure | Air enters the room through leakage paths. | Workers, adjacent rooms and surrounding facility. | USP 800 hazardous drug handling, powder containment, chemical or hazardous processes. | Prevent hazardous material from escaping. |
| Cascade Pressure | Air flows from cleaner or safer spaces toward less clean or containment zones. | Workflow and room hierarchy. | Pharmacies, labs, multi-room cleanroom suites. | Balancing doors, exhaust, returns and supply air. |
Pressure differential is commonly measured in inches of water column. Many hazardous containment applications reference negative pressure around 0.01 to 0.03 in. W.C.; the correct design target must be confirmed against the applicable standard, risk assessment and certification requirements.
USP 795 vs USP 797 vs USP 800
Nonsterile, sterile and hazardous compounding do not use the same room design.
A strong facility plan starts by identifying what is being compounded, whether the preparation is sterile or nonsterile, and whether hazardous drugs are involved.
| Item | USP 795 | USP 797 | USP 800 |
|---|---|---|---|
| Primary Goal | Quality of compounded nonsterile preparations. | Sterility assurance and contamination control for CSPs. | Containment and safe handling of hazardous drugs. |
| Typical Room | Designated nonsterile compounding area. | ISO-classified sterile compounding suite. | Containment secondary engineering control or hazardous drug storage/compounding room. |
| Particle Classification | Usually not ISO-classified by itself. | Uses ISO-classified spaces such as ISO 5 PEC, ISO 7 buffer and ISO 8 ante-room depending on category/configuration. | Depends on sterile vs nonsterile hazardous process. Sterile hazardous rooms need both USP 797 and USP 800 considerations. |
| Pressure | Usually not the main defining feature unless hazardous ingredients are involved. | Positive pressure for non-hazardous sterile compounding environments. | Negative pressure for hazardous containment. |
| Airflow Concern | Powder control, ventilation, cleanable environment and cross-contamination prevention. | HEPA filtration, cleanroom hierarchy, pressure relationship and environmental monitoring. | External exhaust, negative pressure, containment and safe removal of hazardous particles or residue. |
| Common Mistake | Treating nonsterile powder handling as a normal room without considering dust or hazardous material risk. | Focusing only on the hood while ignoring room hierarchy, returns, pressure and cleaning flow. | Creating negative pressure without enough exhaust strategy, monitoring or containment workflow. |
USP 795
Nonsterile Compounding
Relevant for creams, gels, ointments, oral liquids, capsules, powders and other CNSPs. The room may need cleanable finishes, workflow separation, dust awareness and containment planning if hazardous ingredients are handled.
USP 797
Sterile Compounding
Relevant when sterile preparation requires ISO-classified environments, HEPA filtration, cleanroom hierarchy, garbing, cleaning, environmental monitoring and certification support.
USP 800
Hazardous Drug Handling
Relevant when hazardous drugs require containment, negative pressure, external exhaust, careful workflow and worker/environmental protection.
Cleanroom Types & Use Cases
Different rooms serve different compliance and production goals.
| Room Type | Typical Classification | Pressure | What Happens There | Industries | Key Design Focus |
|---|---|---|---|---|---|
| ISO 8 Ante-Room | ISO 8 or applicable classified support space. | Usually positive in non-hazardous sterile suites; pressure relationship depends on layout. | Gowning, material transition, personnel entry, staging. | Pharmacy, medical device, biotech. | Workflow, gowning sequence, doors, pressure relationship, cleaning. |
| ISO 7 Buffer Room | ISO 7. | Positive for non-hazardous sterile; negative if hazardous sterile buffer under USP 800. | Supports ISO 5 PECs and sterile compounding operations. | Pharmacy, hospital, compounding, biotech. | HEPA supply, returns, pressure, particle counts, cleaning and certification. |
| ISO 5 PEC / Critical Zone | ISO 5. | Depends on PEC type and surrounding room. | Critical sterile compounding or highly sensitive work. | Pharmaceutical, sterile compounding, labs. | HEPA integrity, first air, operator technique, placement and certification. |
| USP 800 HD Storage Room | Not necessarily ISO-classified unless tied to sterile compounding. | Negative. | Storage of hazardous drugs. | Pharmacy, oncology, healthcare. | External exhaust, negative pressure, 12 ACPH reference, segregation and monitoring. |
| Nonsterile HD Compounding Room | Usually non-ISO classified but containment-focused. | Negative. | Nonsterile hazardous compounding such as powders, creams or capsules. | Pharmacy, compounding labs. | Containment, exhaust, powder control, cleanable surfaces, workflow. |
| Electronics Cleanroom | Often ISO 7/8 or process-specific controlled environment. | Usually positive. | Assembly, testing, packaging or sensitive process work. | Electronics, aerospace, sensors, advanced manufacturing. | Particle control + ESD flooring/grounding integration. |
Cleanroom Construction Process
A cleanroom project should be planned as a performance system.
Walls, ceilings, flooring, doors, FFUs, returns, HVAC, pressure, electrical and certification support should be coordinated before installation begins.
01 Evaluation
Confirm industry, process, room size, required ISO class, pressure strategy, utilities and compliance expectations.
02 Layout
Define room hierarchy, personnel flow, material flow, doors, equipment locations, returns and service access.
03 System Design
Coordinate modular panels, ceiling grid, FFUs, lighting, HVAC interface, returns, exhaust and flooring requirements.
04 Installation
Install modular envelope, ceiling grid, doors, finishes, flooring, FFUs, returns and mechanical/electrical interfaces.
05 Balancing
Adjust airflow, supply, exhaust and pressure relationships so the room behaves as intended.
06 Cleaning
Perform construction cleanup and cleanroom preparation before certification testing.
07 Verification
Support particle counts, airflow readings, pressure differential verification, HEPA testing and documentation.
08 Handover
Provide project documentation, maintenance considerations and future expansion planning.
Testing & Verification
A cleanroom should be verified, not only installed.
Performance is confirmed through measurements. The right verification scope depends on the standard, process, risk level and certifier requirements.
| Test / Tool | What It Confirms | Why It Matters | Common Use |
|---|---|---|---|
| Particle Counter | Airborne particle concentration at specified particle sizes. | Confirms ISO classification. | ISO 14644 certification and cleanroom verification. |
| Airflow Hood / Balometer | Delivered supply volume from diffusers, HEPA modules or FFUs. | Confirms air delivery and supports ACH calculations. | Cleanroom balancing and certification support. |
| Manometer | Pressure differential between rooms. | Confirms positive or negative pressure strategy. | USP 797 / USP 800 and room hierarchy verification. |
| Smoke Visualization | Direction of airflow and leakage paths. | Shows whether air moves as intended around doors, hoods and equipment. | Pressure cascade and airflow troubleshooting. |
| HEPA Integrity Testing | Filter or seal leakage. | Confirms filtration system integrity. | Critical cleanroom systems and certification support. |
| Temperature / Humidity | Environmental conditions inside the room. | Supports process control, comfort and some ESD considerations. | Pharma, medical device, electronics and manufacturing. |
Industries We Support
Different industries need different cleanroom strategies.
Pharmaceutical
USP 797, USP 800, sterile compounding, hazardous drug handling, room hierarchy, pressure and documentation.
Biotechnology
Controlled environments for sensitive processes, contamination reduction, workflow and cleanable finishes.
Medical Device
ISO 7/8 cleanrooms, packaging, gowning, QA documentation and controlled production areas.
Electronics
Particle control combined with ESD flooring, grounding, personnel controls and sensitive component protection.
Aerospace
Controlled assembly, foreign object debris reduction, cleanable systems and process consistency.
Advanced Manufacturing
Modular controlled environments for dust reduction, defect control and production reliability.
Research Labs
Flexible modular rooms, filtration, pressure control and specialty environmental requirements.
Packaging
ISO 8 or controlled packaging areas for sensitive products, medical devices and clean manufacturing workflows.
Cleanroom FAQ
Technical questions clients usually ask before starting a cleanroom project.
What is an ISO 7 cleanroom?
An ISO 7 cleanroom is a controlled environment with defined particle limits under ISO 14644-1. It is commonly used for sterile buffer rooms, medical device manufacturing, aerospace/electronics and controlled production areas.
What is an ISO 8 cleanroom?
An ISO 8 cleanroom is less stringent than ISO 7 and is commonly used for ante-rooms, gowning, packaging, material transfer and support spaces around cleaner core areas.
What is the difference between USP 795, 797 and 800?
USP 795 applies to nonsterile compounding, USP 797 applies to sterile compounding, and USP 800 applies to hazardous drug handling. A project may involve more than one chapter depending on the process.
Do cleanrooms need positive pressure?
Not always. Positive pressure is used when the room or product must be protected from outside contamination. Negative pressure is used when hazardous material must be contained.
What are low wall returns?
Low wall returns are return grilles placed lower on walls to help guide airflow through the work zone and remove particles from the room. Their placement matters because poor returns can create stagnant zones.
Can more FFUs automatically make a room cleaner?
More FFUs can increase airflow, but they do not automatically fix a poor layout. Return placement, equipment obstruction, pressure strategy, leakage and balancing all affect performance.
What is ACH?
ACH means air changes per hour. It estimates how many times room air volume is supplied or exchanged in one hour. ACH is useful, but it does not replace particle testing or pressure verification.
Can ESD flooring be used inside a cleanroom?
Yes. Some cleanrooms require both particle control and static control. The flooring must support cleanability, ESD performance, grounding continuity and the operational needs of the facility.
Planning a Cleanroom Project?
VIMO INOVA can help evaluate cleanroom layout, airflow, pressure, FFUs, returns, flooring and certification readiness.
Whether your project involves USP 795, USP 797, USP 800, ISO 7, ISO 8, ESD flooring or a modular controlled environment, the right plan should start before construction begins.
Schedule Project Evaluation