What is a Class 100 Cleanroom / ISO5 Cleanroom?

1. What is a Class 100 Cleanroom / ISO5 Cleanroom?

A cleanroom is a room where the concentration of airborne particles is controlled. A Class 100 (ISO5) cleanroom refers to a room where the concentration of particles in the air meets the ISO Class 5 requirements defined by ISO 14644-1. It is one of the higher cleanliness levels commonly used in industrial production, and is widely applied in fields such as sterile pharmaceutical manufacturing, semiconductor lithography, and precision optics.

It's worth noting that "Class 100" is the terminology from the older Federal Standard 209E, which specifies no more than 100 particles ≥0.5 μm per cubic foot of air. Under the current ISO 14644-1 standard, the roughly equivalent classification is ISO Class 5. In practice, "Class 100 cleanroom" and "ISO5 cleanroom" are still used interchangeably across the industry.

2. Cleanliness Standards for Class 100 Cleanroom / ISO5 Cleanroom 

ISO 14644-1 standards for airborne particles in clean areas:

Note: Due to uncertainties in the measurement process, three valid figures are required to determine the concentration classification level.

As shown in the table above, in a Class 100 cleanroom / ISO5 cleanroom, the concentration of particles per cubic meter of air should not exceed:

• 3,520 for particles ≥ 0.5 μm
• 832 for particles ≥ 1.0 μm
• 29 for particles ≥ 5.0 μm

Unlike a Class 10,000 (ISO7) cleanroom, an ISO5 cleanroom also carries explicit limits for particles ≥0.1 μm (100,000/m³) and ≥0.2 μm (23,700/m³). The higher the cleanliness class, the tighter the control required over smaller particles — this matters in processes such as semiconductor lithography and cell therapy manufacturing, where even sub-micron particles can compromise yield or safety.

3. Importance of Particle Control in Class 100 Cleanroom / ISO5 Cleanroom

In semiconductor manufacturing, sterile pharmaceutical production, cell and gene therapy, and precision optics, particle control in an ISO5 environment directly determines product yield, safety, and process success.

Ensuring Product Quality and Yield In the semiconductor industry, advanced process nodes are extremely sensitive to particle contamination. Even a nanometer-scale particle landing on a wafer surface can misalign a lithography pattern, causing a short or open circuit. As process nodes shrink further, more critical steps — lithography, thin-film deposition, ion implantation — must be performed in ISO5 or even higher-classified environments.

Ensuring the Safety of Sterile Drug Products In the pharmaceutical industry, a Class 100 cleanroom typically corresponds to an EU GMP Grade A zone, generally used for the highest-risk operations such as aseptic filling and sealing. Any microbial or particulate contamination entering a zone that directly contacts the drug product can compromise sterility, raise endotoxin levels, or otherwise threaten patient safety.

Ensuring Accuracy and Repeatability in Scientific Research In optical coating, precision instrument assembly, and nanomaterial research, stray particles that settle on samples or optical components can distort results and undermine repeatability — making ISO5-level environments essential for reliable data.

Protecting Patients and Operators In emerging fields like CAR-T cell manufacturing and viral vector production, Class 100 cleanrooms are commonly used for open cell-processing steps and aseptic filling, ensuring cell therapy products remain free of microbial or particulate contamination throughout production.

In short, particle control requirements in a Class 100 cleanroom are considerably stricter than in a Class 10,000 (ISO7) cleanroom. Achieving and maintaining ISO5 cleanliness typically requires a high-efficiency air purification system (primary, medium, and sub-HEPA/HEPA filtration stages, with ULPA filters often needed at critical workstations), a unidirectional (laminar) airflow design, and rigorous management of personnel and material entry to minimize human-introduced contamination.

4. Airflow Design for Class 100 / ISO5 Cleanroom​​​​​​​ 

Unlike the non-unidirectional (turbulent) airflow commonly used in ISO7 cleanrooms, a Class 100 / ISO5 cleanroom generally must use unidirectional (laminar) airflow — air moves in parallel, uniform streamlines (vertically or horizontally) continuously through the space, rapidly sweeping away particles generated in the work area and preventing eddies or stagnant zones, so an extremely low particle concentration can be consistently maintained.

• Vertical unidirectional flow: Air is supplied evenly from ceiling-mounted HEPA/ULPA filters, flows straight down through the work zone, and exits through floor-level or low return grilles. This is the most common configuration for ISO5 cleanrooms and suits scenarios requiring high cleanliness across the entire room.
• Horizontal unidirectional flow: Air is supplied from one wall, flows horizontally across the work zone, and returns through the opposite wall — commonly used for specific process equipment or individual workstations.

For larger facilities where only certain process steps require Class 100 cleanliness (e.g., an ISO7 or ISO8 background environment with a localized Class 100 laminar flow hood, laminar flow bench, or isolator at critical stations), a hybrid design — lower-classification background plus localized Class 100 laminar flow at key workstations — can meet process cleanliness requirements while effectively controlling overall construction and operating costs.

Whichever configuration is used, the HEPA/ULPA filtration units (FFUs or filter boxes) in a Class 100 cleanroom typically need to be installed at full or near-full coverage across the supply-air ceiling to ensure uniform, dead-zone-free airflow across the entire work area. This is one of the main hardware differences between an ISO5 cleanroom and a Class 10,000 (ISO7) cleanroom.

5. Supply Air Velocity and Air Change Rate for Class 100 Cleanroom​​​​​​​

Because an ISO5 cleanroom relies on unidirectional airflow, cleanliness control depends primarily on a stable, uniform face velocity rather than the "air changes per hour" metric used for lower-classification cleanrooms. This is a fundamental difference in how airflow performance is expressed between Class 100 cleanrooms and Class 10,000-and-below cleanrooms.

As shown in the table, the key control parameter for a Class 100 / ISO5 cleanroom is the supply-air face velocity, which should generally be maintained between 0.2 and 0.5 m/s:

• If the velocity is too low, the unidirectional flow and self-cleaning capability are insufficient, allowing particles to linger or disperse within the work zone instead of being swept out of critical areas.
• If the velocity is too high, energy consumption and noise increase, and the airflow may disturb sensitive processes (e.g., precision assembly, open-container filling) or even turn turbulent, undermining the unidirectional characteristic.

In practice, face velocity should be determined based on airflow stability requirements, particle generation rate, opening area, and other process-specific factors, with regular velocity measurement and airflow visualization (smoke tests) at critical workstations to confirm the airflow remains unidirectional and free of eddies.

6. Temperature, Humidity, and Pressure Control in Class 100 Cleanroom​​​​​​​

The principles for temperature and humidity control in a Class 100 cleanroom are broadly similar to those for an ISO7 cleanroom: process requirements come first. Absent specific process requirements, temperature is typically maintained at 18–26°C and relative humidity at 45–65%. However, because ISO5 cleanrooms are often used for highly sensitive processes such as semiconductor lithography and aseptic filling, actual projects frequently tighten these ranges (e.g., ±1–2°C, ±5% RH) to maintain process consistency and support the stable operation of precision equipment such as lithography tools and metrology systems.

The rationale for temperature and humidity control mirrors that of ISO7 cleanrooms: moderately higher humidity helps dissipate static electricity and promotes particle settling, but excessive humidity can cause condensation, product moisture damage, or microbial growth. Humidity that is too low increases static buildup and airborne particle concentration, which is especially detrimental to static-sensitive semiconductor products.

For pressure control, a Class 100 cleanroom is usually the highest-pressure zone within a facility, maintaining positive pressure relative to surrounding lower-classification areas, with a differential of no less than 10 Pa. Cleanliness should increase with pressure, forming a gradient that decreases from the Class 100 core outward, preventing contaminants from lower-grade areas from migrating inward. For cleanrooms handling biological or hazardous materials — where negative pressure is instead required to contain contamination or hazardous emissions — the pressure gradient should be reversed according to safety requirements, paired with a dedicated exhaust air treatment system.

7. Monitoring and Maintenance of Class 100 / ISO5 Cleanroom​​​​​​​ 

Because an ISO5 cleanroom's particle concentration limits are far stricter than those of an ISO7 cleanroom, its monitoring frequency and maintenance requirements are correspondingly higher. Critical workstations (such as filling points or lithography stations) typically require continuous or high-frequency online particle monitoring, combined with microbial monitoring (viable air sampling, settle plates, surface sampling) to ensure the environment remains compliant at all times.

Routine maintenance of a Class 100 cleanroom generally includes:

1. Regular inspection and replacement of filters: Pre-filters are typically cleaned monthly and medium-efficiency filters replaced quarterly. Because Class 100 cleanrooms demand higher-performance terminal filtration, HEPA/ULPA filter integrity testing and replacement frequency should generally exceed that of an ISO7 cleanroom, with regular DOP/PAO leak testing to confirm filtration efficiency (terminal filters should be replaced once resistance reaches twice the initial value).
2. HVAC equipment maintenance: Fans, heat exchangers (cooling/heating coils), humidifiers, and motors should undergo regular performance checks and maintenance, at least twice a year.
3. Calibration of monitoring equipment: Temperature/humidity sensors, pressure sensors, and particle counters should be calibrated on a regular basis, with results recorded; particle counters in Class 100 environments typically require shorter calibration intervals than in lower-classification cleanrooms.

Additionally, Class 100 cleanrooms must follow strict routine cleaning and disinfection protocols for walls, ceilings, floors, and equipment surfaces, with disinfection efficacy validated periodically. Personnel entry and gowning procedures should be closely supervised and documented to minimize human-introduced contamination.

8. Industry Applications and Special Requirements for Class 100 / ISO5 Cleanroom​​​​​​​

Class 100 / ISO5 cleanrooms are widely used in semiconductor manufacturing, biopharmaceuticals, precision optics, and cell and gene therapy — industries where particle contamination has an outsized impact on product outcomes.

Semiconductor and Electronics Industry: ISO5 cleanrooms are primarily used for the process steps most sensitive to particle contamination — lithography, thin-film deposition, ion implantation, and wafer bonding. As process nodes continue to shrink, certain critical steps at leading-edge nodes now require ISO4 or higher, making Class 100 cleanrooms the standard configuration for core wafer fabrication areas.

Biopharmaceutical Industry: In sterile drug manufacturing, a Class 100 cleanroom typically corresponds to an EU GMP Grade A zone (required to achieve ISO5 both "at rest" and "in operation"), used for aseptic filling and sealing, exposure of sterile active ingredients, and other high-risk aseptic operations such as sterile connections. These zones are commonly paired with laminar flow hoods, isolators, or RABS (Restricted Access Barrier Systems) to further limit the impact of personnel activity on critical-zone cleanliness.

Cell and Gene Therapy: In emerging biopharmaceutical fields such as CAR-T cell manufacturing and viral vector filling, Class 100 cleanrooms are commonly used for open cell-processing steps and aseptic filling, ensuring cell therapy products remain free of microbial or particulate contamination throughout production.

Precision Optics and Precision Manufacturing: In high-precision optical coating, precision instrument assembly, and nanomaterial preparation, Class 100 cleanrooms prevent fine particles from settling on product surfaces, safeguarding optical performance, assembly precision, and yield.

For Class 100 cleanrooms handling highly active or hazardous substances (such as certain biologics or cytotoxic drugs), an independent purification HVAC system is required, with exhaust air specially treated (e.g., high-efficiency filtration, chemical scrubbing) to ensure discharged air meets environmental and occupational safety standards.

9. Types, Characteristics, and Advantages of Class 100 Modular Cleanroom​​​​​​​ 

Like Class 100 modular cleanrooms / ISO5 modular cleanrooms in general, this category can be divided into hardwall and softwall types based on structural material. However, because ISO5 cleanliness demands extremely tight sealing and airflow uniformity, nearly all Class 100 cleanrooms in practice use hardwall construction to ensure precise control of temperature, humidity, pressure, and airflow parameters.

Because Class 100 cleanrooms demand far greater airflow uniformity, sealing performance, and parameter stability than ISO7 cleanrooms, hardwall modular construction is, in practice, the standard choice for Class 100 applications.

10. What is the Cost of a Class 100 / ISO5 Modular Cleanroom?   

The cost of a Class 100 / ISO5 modular cleanroom depends on area, ceiling height, material selection, airflow configuration, filtration setup (HEPA vs. ULPA), special process requirements, and supporting infrastructure. Because Class 100 cleanrooms typically require full or high-density filter coverage, more complex airflow design, and higher-precision monitoring systems, the cost per unit area is generally significantly higher than that of a Class 10,000 (ISO7) cleanroom.

Modular construction methods still apply: most components are prefabricated off-site and rapidly assembled on-site, substantially shortening the construction schedule and reducing on-site labor costs. Compared with traditional built-in-place cleanrooms, a modular Class 100 cleanroom can reduce overall cost by roughly 20% and shorten installation time by 40–50%, while also making future upgrades or relocation easier. Specific cost estimates should be developed through a dedicated design proposal based on actual process requirements, layout, and supporting facilities.

11. How to Ensure a Modular Cleanroom Meets Class 100 / ISO5 Cleanroom Requirements​​​​​​​

To ensure a modular cleanroom achieves Class 100 / ISO5 cleanliness, the design must strictly follow ISO5 cleanliness requirements, and all materials used must meet cleanroom standards for not generating or accumulating dust.

Specifically:

1. Filtration system: The purification HVAC system should be equipped with HEPA or, where required, ULPA terminal filters, with filter density determined by the criticality of each process step — critical workstations should generally use full-coverage FFUs or high-density HEPA filter arrays.
2. Airflow organization: The modular cleanroom should be designed for unidirectional (laminar) airflow, with vertical or horizontal face velocity maintained between 0.2 and 0.5 m/s, ensuring uniform airflow free of dead zones or eddies.
3. Pressure and differential: The modular cleanroom must maintain the necessary pressure gradient and proper airflow organization, keeping the Class 100 core area positive relative to surrounding lower-classification zones, with a differential of no less than 10 Pa.
4. Materials and enclosure sealing: Well-sealed, low-particle-generating, cleanable enclosure materials should be used, minimizing seams and dead corners that could harbor or generate particles.

After design and fabrication, the modular cleanroom should undergo rigorous performance testing — including particle counting, airflow velocity testing, airflow visualization, differential pressure testing, temperature/humidity validation, and microbial monitoring where applicable — with a complete validation report issued to confirm that cleanliness, airflow organization, and all environmental parameters meet Class 100 / ISO5 regulatory and standard requirements before the cleanroom is put into operation.