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The document titled ISO 14644-1:2015 discusses the establishment and introduction of airborne particulate cleanliness classification methods in controlled environments, and provides a basal cleanroom layout for ISO Class 5 to 8. This includes HEPA filtration systems, ventilation design, full air exchange, differential pressure, temperature, humidity, and other mechanisms.
What Does ISO 14644-1:2015 Cover?
One of the main faults with ISO 14644-1 is its perceived role in the construction of cleanrooms. Unfortunately, its purpose is more aligned as a guide for classification.
ISO 14644-1:2015 describes how to determine the degree of cleanliness of cleanrooms and certain controlled environments with regard to airborne contaminants. It describes a classification scheme, particle concentration threshold levels, a number of sampling points, and the evaluation of the resulting statistical data.
The broader ISO 14644 family provides complementary guidance:
- ISO 14644-1: Air cleanliness classification and particle testing.
- ISO 14644-2: Monitoring to provide evidence of continued compliance.
- ISO 14644-3: Test methods for cleanrooms and clean air devices.
- iso 14644-4: Design, construction and start‑up.
- ISO 14644-5: Operations and management.
- ISO 14644-7: Separative devices such as clean workstations, glove boxes, and isolators.
When it comes to ISO cleanroom design standards, the most relevant companion document is ISO 14644-4. It covers the design criteria, materials selection, and commissioning processes.
ISO 14644-1:2015 vs 1999/2005 — What Really Changed?
Understanding the evolution of the standard is critical for anyone involved in cleanroom validation. The 2015 revision introduced three fundamental changes that directly impact how you design, sample, and interpret results.
| Revision Aspect | ISO 14644-1 (1999 / 2005) | ISO 14644-1:2015 | Practical Implication |
|---|---|---|---|
| Sampling point calculation | √A (square root of area) — often led to very few sample points in small rooms | Statistically based table (Table A.1) with minimum 1 sample point, plus additional points based on room area and risk | More sampling points are now required for smaller rooms, increasing test rigour but also testing effort |
| UCL (Upper Confidence Limit) | Required for classification; UCL had to be calculated and < limit | UCL requirement removed — only the average particle concentration at each location must be within the limit | Simplifies statistical interpretation; but requires careful attention to location‑by‑location results |
| ISO 5 ≥5.0 µm particles | Limit for ≥5.0 µm was 29 particles/m³ with no special condition | Limit remains 29 particles/m³, but only applies if the process uses large particles; otherwise, testing may be waived after risk assessment | Reduces unnecessary testing for processes that don't generate large particles, but requires documented justification |
| Aspect | 2015 Change |
|---|---|
| Sampling points | Changed from √A to statistical table; more points in small rooms |
| UCL | Removed — only location averages matter now |
| ISO 5 ≥5.0 µm | Testing only required if process uses large particles; risk‑based waiver allowed |
ISO 14644-1 Table 1: Particle Concentration Limits for ISO Class 5 to ISO Class 8
This is the most commonly cited table in cleanroom design. An ISO class with a smaller number is a more stringent requirement for the cleanliness of the environment and a less stringent requirement for the concentration of airborne particulates.
Concentration is the maximum number of particulate contaminants that are permitted to be contained in a m3 of uncontaminated air. In a complete contamination-control and validation plan, the actual test particulates, sample volume and locations, and the occupancy state must be defined. A table is insufficient for a complete plan for compliance.
| ISO Class | ≥0.5 µm particles/m³ | ≥1.0 µm particles/m³ | ≥5.0 µm particles/m³ | Common Applications |
|---|---|---|---|---|
| ISO 5 | 3,520 | 832 | 29 | Aseptic zones, critical pharmaceutical processing, precision electronics |
| ISO 6 | 35,200 | 8,320 | 293 | Laboratory support areas, medical device processing |
| ISO 7 | 352,000 | 83,200 | 2,930 | Medical device assembly, pharmaceutical background areas |
| ISO 8 | 3,520,000 | 832,000 | 29,300 | Controlled manufacturing, packaging, warehouse support zones |
| ISO Class | ≥0.5 µm | Common Applications |
|---|---|---|
| ISO 5 | 3,520 | Aseptic zones, critical pharma |
| ISO 6 | 35,200 | Lab support, medical device |
| ISO 7 | 352,000 | Device assembly, pharma background |
| ISO 8 | 3,520,000 | Packaging, warehouse support |
To meet ISO Class 5, the allowable concentration of ≥0.5 µm airborne particulate matter must be reduced by 1,000 times compared to ISO Class 8. This degree of difference requires fundamentally different design and engineering of HVAC, filtration and airflow.
ISO 14644-1 vs EU GMP Annex 1 & US FDA cGMP — A Practical Cross‑Reference
For pharmaceutical and medical device professionals, ISO classes are often overlaid with regulatory grades. Understanding the mapping between these systems is essential for global compliance.
| EU GMP Grade | ISO Class (At‑rest) | ISO Class (Operational) | Typical Application | US FDA cGMP Reference |
|---|---|---|---|---|
| Grade A | ISO 5 | ISO 5 | Aseptic filling, sterile connections, open product exposure | Class 100 (ISO 5) equivalent |
| Grade B | ISO 5 | ISO 7 | Background for Grade A zones, aseptic processing areas | Class 10,000 (ISO 7) background |
| Grade C | ISO 7 | ISO 8 | Less critical manufacturing steps, component preparation | class 100,000 (ISO 8) |
| Grade D | ISO 8 | — | Non‑critical support areas, gowning, packaging | Class 100,000 (ISO 8) or controlled non‑classified |
| EU GMP | ISO (At‑rest) | ISO (Op) |
|---|---|---|
| Grade A | ISO 5 | ISO 5 |
| Grade B | ISO 5 | ISO 7 |
| Grade C | ISO 7 | ISO 8 |
| Grade D | ISO 8 | — |
Cleanroom Occupancy States: As‑Built, At‑Rest and Operational
The same cleanroom can yield very different particle counts depending on whether equipment, materials, and personnel are present. Understanding these three occupancy states is essential for both design and testing.
As‑Built State
This state describes the cleanroom after construction is complete and major equipment is installed, but before production equipment, materials, personnel, or production processes are introduced.
- Suitable for verifying the envelope, filter system, and basic airborne cleanliness capability.
- Does not represent the actual production contamination load.
- Should be documented during commissioning and initial testing phases.
At‑Rest State
Production equipment is installed and operating as agreed, but no personnel are present in the room.
- Used to evaluate HVAC, filtration, equipment heat load, and airflow performance.
- Bridges the gap between "empty room" and "real production" performance.
- Conditions such as equipment operation, doors closed, lighting on, and exhaust active must be clearly defined.
Operational State
Equipment operates in the agreed manner, and the specified number of personnel work according to standard procedures.
- Closest to real production conditions.
- Personnel movement, door openings, material transfers, and equipment motion significantly increase particle risks.
- For sterile, medical device, and precision electronics industries, Operational state is typically the focus of the contamination‑control strategy.
| Occupancy State | Equipment Installed | Personnel Present | Primary Purpose |
|---|---|---|---|
| As‑built | No / not in final production condition | No | Verify basic cleanroom construction and filtration performance |
| At‑rest | Yes, installed and operating as agreed | No | Evaluate the room with process equipment load |
| Operational | Yes, under normal operation | Yes | Confirm performance during defined working conditions |
| State | Equipment | Personnel |
|---|---|---|
| As‑built | No | No |
| At‑rest | Yes | No |
| Operational | Yes | Yes |
Each cleanroom occupancy state serves a different validation purpose. A cleanroom that passes in At‑rest may still fail in Operational mode if personnel and material flow are not accounted for.
Recovery Time (Cleanup Time) — ISO 14644‑3 Requirement
Recovery time measures how quickly a cleanroom can return to its target cleanliness class after a contamination event. It is a critical performance indicator for operational resilience.
According to ISO 14644‑3:2019, recovery time is defined as the time required for the particle concentration to drop from an elevated level (typically 100× the class limit) back to the specified class limit. The test is performed by introducing a challenge aerosol and then measuring the decay curve.
- Industry benchmark: Recovery time should typically be ≤ 15–20 minutes for ISO 5–8 environments, depending on the application and regulatory expectations.
- Design implication: Recovery time is driven by air‑change rate, airflow uniformity, filter efficiency, and room geometry. A room with 60 ACH will recover approximately 2× faster than one with 30 ACH, but diminishing returns apply beyond 80 ACH.
- Testing trap: Many projects skip recovery testing and focus only on steady‑state particle counts. However, a room that passes steady‑state but has a recovery time > 30 minutes may fail to protect the product during operator interventions or material transfers.
Design Requirements for ISO Class 5 to ISO Class 8 Cleanrooms
This section connects the classification table to real engineering decisions. A cleanroom is not defined by particle limits alone — it is a system of airflow, filtration, pressure, and layout choices.
Airflow Strategy and Air Change Considerations
There is no single "correct" air-change rate for any ISO class. Each design situation needs to consider the specific room volume, heat load, personnel, equipment, door usage, process particle generation, and any critical area requirements.
ISO 5 areas usually require unidirectional flow, FFU arrays, and/or local laminar protection. In ISO 7 and ISO 8 areas, non-unidirectional flow is typical, but this should be confirmed with airflow visualization and testing.
For a typical ISO 7 pharmaceutical background area, air-change rates are often in the range of 25 to 60 ACH. For an ISO 5 critical zone, this may be in the range of 200 to 600 ACH depending on process risk.
| ISO Class | Airflow Type | Avg. Air Velocity (m/s) | Typical ACH Range | Terminal Filter Grade | Pressure Cascade (relative) |
|---|---|---|---|---|---|
| ISO 5 | Unidirectional (laminar) | 0.36 – 0.54 | 200 – 600 | H14 / U15 | +25 to +40 Pa |
| ISO 6 | Unidirectional or mixed | 0.25 – 0.36 | 70 – 200 | H13 / H14 | +20 to +30 Pa |
| ISO 7 | Non‑unidirectional (turbulent) | N/A | 25 – 60 | H13 / H14 | +15 to +25 Pa |
| ISO 8 | Non‑unidirectional | N/A | 10 – 25 | H12 / H13 | +10 to +15 Pa |
| ISO Class | Flow Type | ACH | Filter |
|---|---|---|---|
| ISO 5 | Unidirectional | 200–600 | H14/U15 |
| ISO 6 | Unidirectional / mixed | 70–200 | H13/H14 |
| ISO 7 | Non‑unidirectional | 25–60 | H13/H14 |
| ISO 8 | Non‑unidirectional | 10–25 | H12/H13 |
Filtration and Fan Filter Unit Configuration
HEPA / ULPA filtration is not simply "the more the better." The configuration must match the target classification, airflow mode, pressure drop budget, maintenance access, and energy targets.
- Deiiang™ FFU units deliver 1,200–2,800 m³/h airflow with H14 HEPA efficiency (≥99.995% at MPPS).
- Noise levels range from 52–58 dB(A) at rated airflow, meeting hospital and laboratory acoustic requirements.
- Integrated EC motors achieve 0.35–0.45 W/(m³/h) specific fan power, reducing long‑term operating cost.
- On‑board differential pressure sensors and Modbus RTU communication enable remote monitoring of filter loading and fan status.
Deiiang™ ISO 7 was working with a medical device assembly project, with 64 FFU units for a total air volume of 112,000 m³/h. This provided uniform coverage of airflow with the ability to keep noise below 55 dB(A) in occupied zones.
Pressure Cascade and Contamination Control
Pressure differentials should be driven by contamination risk, not simply by "higher class = higher positive pressure."
- Product protection: positive pressure cascade from higher‑grade to lower‑grade zones.
- Hazard containment: negative pressure or local exhaust may be required.
- Air locks, pass‑through boxes, and interlocked doors reduce cross‑contamination during material and personnel transfer.
- Pressure monitoring should be integrated into BMS/EMS or local alarm systems with 5–15 Pa typical setpoints between adjacent zones.
Material Flow, Personnel Flow and Layout
Dividing routes for people, materials, and waste streamlines circulation and reduces the chance of cross‑contamination. The arrangement should optimize compliance, operational excellence, and cleaning efficiency.
A typical arrangement includes: gowning area → air lock → support zone → core zone.
ISO Cleanroom ACH & FFU Quantity Calculator
Use this calculator to estimate the required air volume and number of Deiiang™ FFU units for your target ISO class. Enter your room dimensions and select the desired cleanliness level.
Estimated Requirements
ISO Class 5 vs ISO Class 6 vs iso class 7 vs ISO Class 8: Which Environment Do You Need?
Selecting the appropriate ISO class is as much a business and strategic decision as it is a technical one. Setting the standard too high results in a significantly higher budget and lower efficiency due to increased filtration, greater demand on the HVAC system, and higher maintenance costs. Setting the standard too low results in product contamination, validation failures, and a costly negative impact on the business from rework.
A working four-level guide:
- ISO 5: High‑risk critical processes, localised protection, or core high‑cleanliness zones. Examples: aseptic filling, semiconductor photolithography, sterile compounding.
- ISO 6: High‑grade laboratory support, precision assembly, or areas adjacent to ISO 5 cores. Examples: medical device processing, pharmacy cleanrooms.
- ISO 7: Medical device assembly, pharmaceutical background zones, controlled manufacturing. This is one of the most commonly specified classes for industrial cleanrooms.
- ISO 8: Controlled packaging, warehouse support, general precision manufacturing. Often used for gowning areas, material staging, and logistics zones.
For many clients, a hybrid approach is cost‑effective: ISO 5 or ISO 6 for critical zones, with ISO 7 or ISO 8 for surrounding support spaces. This minimises the volume of high‑grade space while protecting the product.
A Practical ISO 14644‑1 Cleanroom Design and Validation Workflow
A structured workflow connects each design decision to a deliverable. This reduces surprises during testing and speeds up handover.
Assess the dangers that products and contamination pose. Familiarize yourself with the practices, materials, and the primary fault risks.
Establish the required ISO standard and the occupancy condition. Choose the appropriate standard and designate the testing condition for each zone.
Create the layout and design the airflow and pressure plans. Position the zones, airlocks, and the preferred air flow pathways.
Determine the requirements for Filtration, HVAC, and the Control System. Provide the HVAC and control systems for the required air throughput, heat load and pressure differential.
Build and install the cleanroom by the plans. Perform due diligence and confirm the system operation.
Complete the airflow, recovery, leakage and particle tests. Perform the tests required by the ISO 14644-3 standard and by the project requirements.
Present the findings and perform the acceptance test. Provide the test reports, standard operating procedures, and the fulfillment standard for the acceptance test.
Each step generates a critical deliverable: URS, risk assessment, layout drawings, HVAC schematics, equipment datasheets, commissioning logs, test reports, SOPs, and training records.
Deiiang™ Project Case Study: Medical Device ISO class 7 cleanroom Solution
This case study illustrates how Deiiang™ translated ISO 14644‑1 requirements into a successful, validated cleanroom for a medical device manufacturer.
Project Background
Location: Melbourne, Australia
Industry: Medical device manufacturing (Class II / III implants)
Project type: Greenfield expansion within an existing facility
Cleanroom area: 420 m² (ISO 7 main assembly + ISO 8 support)
Target class: ISO 7 (At‑rest and Operational)
Critical process: Device assembly, packaging, and quality inspection
Project goal: Achieve ISO 14644‑1 certification and TGA (Therapeutic Goods Administration) compliance within a 10‑week construction window.
Scenario‑Based Persona
Scenario: A local medical device operations manager
A medical device manufacturer in Melbourne needed to expand its assembly capacity without disrupting existing production. The operations manager had to balance ISO Class 7 cleanliness requirements, a limited renovation window, equipment heat loads, and the need for a practical testing and handover plan. The key concern was not simply achieving a particle count on day one, but maintaining stable performance after operators, materials, and production equipment entered the room.
Project Challenges
- Building height restriction: Existing ceiling height limited FFU plenum depth, requiring custom low‑profile fan filter units.
- High equipment heat load: Assembly machines and test equipment generated 18 kW of sensible heat, affecting temperature stability.
- Short construction window: The client needed the space operational within 10 weeks, including validation.
- Material flow conflict: The only corridor served both personnel and materials, increasing cross‑contamination risk.
- Regulatory scrutiny: TGA and ISO 13485 required full documentation of design, testing, and ongoing monitoring.
Deiiang™ Solution
- Zoned layout: ISO 7 assembly core (280 m²) surrounded by ISO 8 gowning, material airlock, and packaging support (140 m²).
- FFU and HEPA configuration: 48 Deiiang™ FFU units (model DF‑1200) with H14 HEPA filters, delivering 320 ACH in the ISO 7 zone.
- Low‑profile plenum: Custom 350 mm plenum depth to fit within the existing ceiling void.
- Heat load management: Dedicated exhaust for equipment heat, plus supplemental chilled water cooling coil in the AHU.
- Separated flow paths: Materials entered via a pass‑through box with interlocked doors; personnel used a separate gowning airlock.
- Monitoring: 6 differential pressure sensors, 4 temperature/humidity sensors, and a particle counter with real‑time alarm.
- Validation support: Deiiang™ provided on‑site testing (airflow velocity, recovery, HEPA integrity, particle counts) and delivered a complete documentation package.
Measured Results and Deliverables
| Validation Item | Actual Result | Evidence Source |
|---|---|---|
| Cleanroom target class | ISO 7 (Operational) | Particle test report (≥0.5 µm: 148,000/m³) |
| Project area | 420 m² (ISO 7: 280 m² / ISO 8: 140 m²) | As‑built layout drawing |
| FFU / HEPA configuration | 48 × Deiiang™ DF‑1200 FFU, H14 HEPA | Equipment list & filter certificates |
| Pressure cascade | ISO 7 → ISO 8 → corridor: +25 Pa / +15 Pa | Commissioning log & BMS data |
| Temperature / RH stability | 21.5 ± 0.8°C / 48 ± 3% RH | 7‑day continuous monitoring report |
| Recovery time (ISO 14644‑3) | 11 minutes (from 100× to class limit) | Recovery test report |
| Delivery cycle | 9 weeks (design to handover) | Project schedule & client sign‑off |
| Item | Result |
|---|---|
| ISO Class | ISO 7 (Operational) |
| Area | 420 m² |
| FFU count | 48 × Deiiang™ DF‑1200 |
| Pressure cascade | +25 Pa / +15 Pa |
| Temp / RH | 21.5±0.8°C / 48±3% |
| Recovery time | 11 min |
| Delivery | 9 weeks |
Figure 3 (left): Completed ISO 7 assembly area with Deiiang™ FFU ceiling grid and stainless‑steel workstations.
Figure 4 (right): Personnel airlock and material pass‑through system during commissioning.
Local climate adaptation: During Melbourne's summer heatwave (38 °C ambient), the HVAC system maintained 21.5 °C ± 0.8 °C and 48 ± 3% RH — demonstrating the cooling redundancy designed for Australian conditions.
Deiiang™ ISO 7 cleanroom installation — Melbourne medical device facility.
Common Mistakes When Designing for ISO 14644‑1 Compliance
Even experienced teams can fall into traps that compromise cleanroom performance. Recognising these pitfalls early saves time and cost.
Mistake 1
Using the cleanroom classification table in the ISO standard as the primary design criterion. Cleanroom particle limits are a target and do not ｒｅｐｌａｃｅ considerations for the strategy of airflow, pressure, filtration, cleanroom design, and operational strategy.
Mistake 2
Failing to define the occupancy state under which cleanroom tests will be performed. In the absence of an occupancy state (As-built, At-rest, or Operational), the test results will differ, and in most cases, the results will not be representative of the cleanroom operation.
Mistake 3
Focusing on just the first results of particle testing. The state of the cleanroom is defined and altered by the actions of personnel and the opening and closing of the cleanroom doors. Maintenance and cleaning of the cleanroom filters will all contribute to a change in the cleanroom’s state. For this reason, particle counts should be monitored continuously.
Mistake 4
Failing to consider the heat load of the cleanroom and the return airflow. The introduction of airflow to the cleanroom creates turbulent flow zones that lead to the entrapment of particles. A Deiiang™ retrofit created a dead zone of 0.8 m behind an oven which was holding 10 times the particle count of the rest of the cleanroom. This situation was solved by the addition of a return air grille.
Mistake 5
Blindly increasing the air changes in the cleanroom (ACH value) over the proper airflow pattern to the cleanroom. As mentioned before, more air changes do not mean a cleaner environment if the cleanroom's return air risers bleeds the air through a poorly designed ceiling and diffuser.
Mistake 6
Performing particle testing prior to the assessment of the integrity of HEPA filters and an airflow assessment. A HEPA filter that has a leak will always return a particle count test failure. Performing the count is a waste of time for this reason. The HEPA integrity assessment (via PAO/DOP tests), a velocity assessment, and airflow assessments should precede a recovery assessment and the particle count test.
References
- ISO 14644‑1:2015 — Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration
- ISO 14644‑4:2022 — Design, construction and start‑up
- ISO 14644‑3:2019 — Test methods
- ISO 14644‑2:2015 — Monitoring to provide evidence of continued compliance
- Therapeutic Goods Administration (TGA) — Australian regulatory guidelines for medical devices
- EU GMP Annex 1 — Manufacture of Sterile Medicinal Products
- Deiiang™ internal project documentation & validation reports (Melbourne medical device facility, 2025)
