Knowledge Base
ISO 14644 cleanroom reference. ISO Class 1–9 particle count table (ISO 14644-1:2015), air changes and HEPA requirements, gowning protocols by class (ISO 14644-5:2022), material restrictions, cleanroom hardware selection, ESD in cleanrooms and monitoring requirements.
ISO 14644-1:2015
A cleanroom is a controlled environment in which the concentration of airborne particles is regulated. ISO 14644-1:2015 defines nine cleanroom classes (ISO 1–ISO 9) based on maximum allowable particle concentrations per cubic metre of air at specified particle sizes. ISO 1 is the most stringent; ISO 9 is equivalent to a normal room. ISO 14644-1:2015
| 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 | FED-STD-209E Equiv. | Typical Application |
|---|---|---|---|---|---|---|---|---|
| ISO 1 | 10 | 2 | — | — | — | — | — | Research, advanced semiconductor R&D |
| ISO 2 | 100 | 24 | 10 | 4 | — | — | — | Semiconductor research |
| ISO 3 | 1,000 | 237 | 102 | 35 | 8 | — | Class 1 | Semiconductor wafer fab (advanced nodes) |
| ISO 4 | 10,000 | 2,370 | 1,020 | 352 | 83 | — | Class 10 | Hard disk, advanced semiconductor |
| ISO 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | 29 | Class 100 | Pharmaceutical aseptic fill, advanced PCB, wafer fab |
| ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 | Class 1,000 | Medical device assembly, optics, electronics |
| ISO 7 | — | — | — | 352,000 | 83,200 | 2,930 | Class 10,000 | Electronics assembly, pharmaceutical non-sterile, medical device |
| ISO 8 | — | — | — | 3,520,000 | 832,000 | 29,300 | Class 100,000 | General electronics manufacturing, aerospace |
| ISO 9 | — | — | — | 35,200,000 | 8,320,000 | 293,000 | Room air (approx.) | Controlled environment; general assembly |
Source: ISO 14644-1:2015 Table 1. FED-STD-209E was withdrawn in 2001 but values are included for reference. "—" indicates the particle size is not used for classification at that class. Measured at agreed sampling locations with statistical sampling per ISO 14644-1 Annex B.
| ISO Class | Typical Air Changes/Hour (ACH) | HVAC Filter Type | Typical Pressure Differential |
|---|---|---|---|
| ISO 5 | 240–480+ | ULPA (99.9995% @ 0.12 µm) | ≥15 Pa above adjacent |
| ISO 6 | 90–180 | HEPA (99.97% @ 0.3 µm) or ULPA | ≥12 Pa above adjacent |
| ISO 7 | 30–60 | HEPA (99.97% @ 0.3 µm) | ≥10 Pa above adjacent |
| ISO 8 | 10–25 | HEPA (99.97% @ 0.3 µm) | ≥5 Pa above adjacent |
| ISO 9 | 5–10 | High-efficiency pre-filter + HEPA | — |
Air change rates are design guidelines — actual requirements depend on occupancy, process, heat load and contamination sources. Cleanrooms operate at positive pressure relative to adjacent areas (cascade pressure) to prevent particle ingress when doors open.
ISO 14644-5 / ISO 14644-1
Gowning protocol controls the largest source of contamination in a cleanroom — people. Garments must capture shed skin cells, hair, fibres and moisture. ISO 14644-5 (revised 2022) covers operational requirements including gowning. ISO 14644-5:2022 ISO 14644-1:2015
| ISO Class | Head Cover | Body Garment | Foot Cover | Gloves | Face | Gowning Area Required |
|---|---|---|---|---|---|---|
| ISO 3–4 | Full hood (all hair and ears covered) | Full coverall (bunny suit), double-layered | Cleanroom boots + overshoes | Double glove (sterile outer) | Full face mask + goggles or visor | Full gowning room with HEPA airlock |
| ISO 5 | Full hood | Full coverall (bunny suit) | Dedicated cleanroom boots or overshoes | Single or double nitrile/latex glove | Face mask + safety glasses | Gowning room with airlock preferred |
| ISO 6 | Hood or bouffant cap covering all hair | Coverall or cleanroom frock | Overshoes over street footwear | Single glove | Face mask | Gowning anteroom |
| ISO 7 | Bouffant cap — full hair coverage | Cleanroom frock or lab coat (lint-free) | Overshoes or cleanroom shoe covers | Gloves recommended | Mask recommended | Bench demarcation or anteroom |
| ISO 8 | Bouffant cap — full hair coverage | Lab coat or frock (low-lint) | Shoe covers | Optional | Optional | Bench demarcation or gowning area |
| ISO 9 | Bouffant or hair net | Lab coat optional | Optional | Optional | Optional | Minimal — as documented |
Garments must be manufactured from low-linting synthetic materials (typically continuous-filament polyester). Laundering must be performed by approved cleanroom laundry facilities — home laundering is not acceptable for ISO 5 and above. Garment particle emission per IEST-RP-CC003.
| Step | Action | Notes |
|---|---|---|
| 1 | Hand hygiene — wash hands and forearms for ≥30 s | Before any gowning begins |
| 2 | Don bouffant cap or hood — cover all hair and ears | Work from crown outward; no hair visible |
| 3 | Apply shoe covers or change into cleanroom footwear | Do not cross bench/demarcation with street footwear |
| 4 | Don coverall or frock — touch inner surfaces only | Coverall must not contact floor |
| 5 | Zip/fasten all closures completely | No gaps at collar, cuffs or ankles |
| 6 | Don face mask; ensure full nose and chin coverage | Mask ties behind head, not ears, for ISO 5 and above |
| 7 | Don first glove layer | Wrist of glove should overlap coverall cuff |
| 8 | Don second sterile glove (ISO 5 and below) | Outer glove changed frequently during work |
| 9 | Mirror check — verify full coverage before entry | No exposed skin, hair or street clothing visible |
| 10 | Enter cleanroom through airlock / pass-through | Do not hold door open; allow pressure equalisation |
Gowning effectiveness should be verified periodically by contamination fingerprint testing (glove fingertip testing, garment settle plate monitoring). Training records must be maintained.
ISO 14644-5 / IEST-RP-CC series
Many common materials are prohibited or restricted in cleanrooms due to particle generation, outgassing or chemical contamination risks. Material selection must be reviewed against the ISO class and process requirements. ISO 14644-5:2022
| Material / Item | Status in Cleanroom | Reason | Alternative |
|---|---|---|---|
| Standard cardboard / corrugated boxes | Prohibited | High particle generation; fibre shedding | Cleanroom-grade plastic totes, vacuum-packed cleanroom packaging |
| Pencils and graphite pencils | Prohibited ISO 5 and above | Graphite particle contamination | Cleanroom ballpoint pens or laser printing |
| Standard sticky notes (paper) | Restricted | Paper fibre shedding | Cleanroom-grade polyester labels or electronic notation |
| Standard tape | Restricted/prohibited | Adhesive outgassing; particle trapping | Cleanroom-grade polyimide or polyester tape |
| Cotton garments, street clothing | Prohibited | High fibre particle emission | Approved cleanroom coveralls |
| Wood products (pallets, furniture) | Prohibited | Splinter and fibre generation | Stainless steel, anodised aluminium, ESD plastic |
| Standard lubricants and oils | Restricted | Hydrocarbon outgassing, molecular contamination | Low-outgassing dry lubricants, cleanroom-grade oils |
| Standard plastics (PVC, ABS, polystyrene) | Restricted | Particle generation, plasticiser outgassing | PEEK, PTFE, polypropylene, ultra-pure polyethylene |
| Food and drink | Prohibited | Particulate and microbial contamination | Consumed outside gowning zone only |
| Cosmetics, perfume, hand cream | Prohibited | Molecular contamination, particle generation | None — personal hygiene restrictions apply |
| Personal mobile devices | Restricted or prohibited | Particle generation, contamination | Cleanroom-grade communication devices where required |
| Standard paper documents | Restricted | Fibre shedding | Laminated documents, digital displays, cleanroom notepads |
Materials entering cleanrooms at ISO 5 and above should be pre-cleaned, double-bagged and passed through material airlocks or pass-through hatches. Packaging materials must be removed progressively as items move to higher cleanliness zones.
| Property Requirement | Preferred Materials | Avoid |
|---|---|---|
| Low particle emission | Electropolished stainless steel (316L), PEEK, PTFE, anodised aluminium | Porous plastics, painted surfaces, rubber (standard) |
| Chemical resistance | PTFE, Hastelloy, PFA, PEEK | Standard carbon steel, zinc coatings, cadmium |
| Low outgassing | PTFE, PEEK, electropolished SS, ultra-high purity PE | PVC, ABS, standard adhesives, foam rubber |
| ESD control + cleanroom | Carbon-loaded PEEK, dissipative PTFE, treated nylon | Standard metals (tribo-charging), uncontrolled plastics |
| Fasteners and hardware | Electropolished 316L stainless, PEEK screws, ceramic | Standard carbon steel, brass, plated fasteners |
Outgassing is measured by total mass loss (TML) and collected volatile condensable material (CVCM) per ASTM E595. For semiconductor cleanrooms, materials should also meet wafer contamination requirements for trace metals and molecular contamination.
IEC 61340-5-1 / ISO 14644
Cleanrooms introduce specific ESD challenges. The low humidity typically required for particle control increases charge generation. Non-ESD-rated cleanroom materials (garments, flooring, bench covers) can be strongly triboelectric. ESD and cleanroom requirements must be designed together. IEC 61340-5-1:2024 ISO 14644-1:2015
| Challenge | ESD Impact | Recommended Solution |
|---|---|---|
| Low humidity (<35% RH) | Reduced natural charge dissipation; higher charge generation on insulating materials | Humidification where process permits; ionisation; more frequent wrist strap checking |
| PTFE and Teflon components | Strong triboelectric charge generator; cannot be grounded | Ionisation to neutralise; minimise surface area; maintain >30 cm from ESDS |
| Cleanroom garments | Many garment materials are insulating unless specifically ESD-rated | Specify ANSI/ESD STM2.1-compliant groundable garments; verify resistance |
| Anti-static floor finishes | Some ESD flooring coatings generate particulates | Specify ESD flooring per ANSI/ESD S7.1 and verify cleanroom particle spec |
| Ioniser placement | Ion flow disturbs laminar air flow in ISO 5 and above | HVAC-integrated room ionisation preferred over bench units in high-class rooms |
| Packaging removal at airlock | Shielding bags removed at EPA entry; ESDS items must remain protected | Pre-stage in cleanroom-rated dissipative trays; remove outer packaging only |
| Cleanroom wipes and swabs | Some cleanroom wipes are triboelectric | Specify pre-saturated, low-tribocharge cleanroom wipes; verify ESD properties |
In semiconductor wafer fabs (ISO 3–ISO 5), ESD and contamination control are integrated. Wafer-handling equipment must simultaneously meet ANSI/ESD SP10.1 (automated handler) and ISO 14644 requirements.
| Relative Humidity | ESD Risk | Typical Charge on Personnel | Notes |
|---|---|---|---|
| < 20% RH | Very high | > 20,000 V possible | Extremely dry — arctic winter, some semiconductor fabs |
| 20–30% RH | High | 5,000–20,000 V | Dry office/fab conditions without ESD controls |
| 30–50% RH | Moderate | 1,000–5,000 V | Typical controlled environment; ESD controls still required |
| 50–65% RH | Lower | < 1,000 V | Improved but not sufficient without grounding and controls |
| > 65% RH | Low (but condensation risk) | < 500 V | Condensation risk on cold surfaces at high RH |
RH targets are typically 40–60% in general EPAs. Semiconductor fabs may operate at <40% RH for process reasons, requiring enhanced ESD controls. IEC 61340-5-1 does not mandate a specific RH — it requires that the ESD programme addresses the actual environmental conditions.
ISO 14644-2:2015
ISO 14644-2:2015 defines requirements for monitoring and demonstrating continuing compliance with cleanliness classifications established per ISO 14644-1. Regular particle monitoring, pressure differential checks and personnel monitoring are required. ISO 14644-2:2015
| Monitoring Parameter | Test Method | Minimum Frequency (typical) | Pass/Fail Criterion |
|---|---|---|---|
| Airborne particle count — classification | ISO 14644-1 Annex B statistical sampling | 6–12 monthly (reclassification) | Per ISO class limits (Table 1) |
| Airborne particle count — routine monitoring | Continuous or periodic sampling at defined locations | Defined in monitoring plan | Alert and action limits defined by facility |
| Pressure differential (room to adjacent) | Calibrated magnehelic or differential pressure gauge | Continuous (alarmed) | ≥5–15 Pa (class dependent); alarm on loss of differential |
| Air change rate / air velocity | Anemometer at HEPA/ULPA filter face | 6–12 monthly or after HVAC maintenance | Design specification ±20% |
| HEPA/ULPA filter integrity | Aerosol photometer (DOP/PAO) scan | Annually or after filter replacement | < 0.01% penetration at any point |
| Temperature | Calibrated probe at defined locations | Continuous | Typically 20–22 °C ± 1 °C (process dependent) |
| Relative humidity | Calibrated hygrometer | Continuous | Typically 40–60% RH ± 5% (process dependent) |
| Personnel particle contribution | Cleanroom garment settle plate / glove fingertip test | Qualification and after retraining | Facility-defined alert/action limits |
| Viable particle monitoring (pharma/medical) | Active air sampling + settle plates (ISO 14698-1) | Per risk assessment | ISO class and regulatory requirement dependent |
Monitoring data must be recorded, trended and reviewed. Excursions must trigger investigation and corrective action. ISO 14644-2 requires a monitoring plan documenting locations, frequency, sample sizes and action levels.
References
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