ISO 8 Cleanroom Requirements: Limits, ACH, Pressure, Gowning

An ISO 8 cleanroom is the least stringent classified cleanroom in common use: no more than 3,520,000 particles of 0.5 micron and larger per cubic meter, the old Class 100,000. It is the grade of gowning rooms and ante-rooms, of non-sterile pharmaceutical manufacturing, of medical device assembly and packaging where the sterilization validation allows it, of nutraceutical and cosmetic filling, and of the Grade D support areas around a sterile suite. It is also the room most often over-specified, because a great deal of work that gets an ISO 8 label needs a controlled environment and not a classified one. This page sets out what ISO 8 actually requires and how to decide whether you need it.

The particle limits

Particle size	ISO 8 maximum per m3	ISO 7	Ordinary room air (about ISO 9)
0.5 micron and larger	3,520,000	352,000	35,200,000
1 micron and larger	832,000	83,200	8,320,000
5 micron and larger	29,300	2,930	293,000

ISO 8 is one class cleaner than ordinary indoor air and one class dirtier than ISO 7. The limit applies at every sampling location in the stated occupancy state. Because the margin over room air is only one order of magnitude, an ISO 8 room is achievable with modest air handling inside an existing building shell, which is the reason it is the usual first cleanroom a growing manufacturer builds.

Air changes and airflow

ISO 14644-1 sets no air change rate. Design practice for ISO 8 is commonly 10 to 25 air changes per hour of HEPA-filtered supply, with design guides quoting a range as wide as 5 to 48 depending on occupancy and process; USP 797 requires at least 20 for an ISO 8 ante-room. Airflow is turbulent, with ceiling HEPA terminals and low wall returns. Because the rate is low, ISO 8 can often be served by a conventional air handler with terminal HEPA filters rather than a dedicated cleanroom unit, and it can frequently be built inside an existing HVAC zone with a fan-filter unit ceiling.

Pressure

An ISO 8 room is held positive to unclassified space and negative to any ISO 7 room it serves, so the cascade steps down from the cleanest room outward. Guidance figures are 10 to 15 pascals (0.04 to 0.06 inches of water) between adjacent grades, and at least 5 pascals to the unclassified corridor. A single door with a closer is acceptable to unclassified space in many designs; entry to an ISO 7 room from the ISO 8 room goes through a gowning airlock. Where ISO 8 is used for containment, for example non-sterile hazardous drug compounding, the room is held negative instead.

How ISO 8 maps to GMP grades

EU GMP Annex 1 Grade D is ISO 8 at rest with no in-operation particle limit defined; Grade C is ISO 8 in operation. The FDA aseptic guidance treats ISO 8 as the lowest classified support grade. Annex 1 microbial limits for Grade D are 200 CFU per cubic meter of air, 100 CFU per 4-hour settle plate and 50 CFU per contact plate. Non-sterile drug manufacturing under 21 CFR 211 does not require a classified room at all; ISO 8 is chosen there as a defensible way to demonstrate the control the regulation expects.

Gowning

ISO 8 gowning is the lightest of the classified grades: hair cover, beard cover where applicable, a frock or lab coat of low-linting fabric, shoe covers or dedicated footwear, and gloves where the product requires them. A gowning area with a bench or line is expected but a full airlock often is not. For a Grade D room Annex 1 expects hair and beard covering and a general protective suit and appropriate shoes. An ISO 8 ante-room to an ISO 7 room is itself the gowning room for the higher grade, which shapes its size and layout.

Materials and construction

Cleanable, non-shedding surfaces: modular panels or epoxy-painted drywall with sealed joints, coved resilient or resinous flooring, flush light fixtures, sealed penetrations and windows with no ledges. The envelope needs to hold a modest pressure differential, which is less demanding than for ISO 7 but still requires every penetration to be sealed. ISO 8 is the class most often built in an existing building; the constraints there are ceiling height for the HEPA plenum, structural support for the ceiling grid, and finding return paths that do not cross other spaces.

Certification tests

Particle counts at the number of locations ISO 14644-1 derives from floor area, each sample at least 2 liters, in the specified occupancy state; installed HEPA filter leak testing; airflow volume and air change verification; and pressure differentials. Recovery time and smoke visualization are rarely specified for ISO 8. ISO 14644-2 sets requalification at a maximum of 12 months for ISO 6 and coarser, with airflow and pressure checked more often under the monitoring plan.

Where ISO 8 is the right answer

Gowning rooms and ante-rooms serving ISO 7 suites, including the USP 797 ante-room.
Non-sterile pharmaceutical manufacturing: oral solid dose, liquids, creams and ointments.
Medical device assembly and packaging where the sterilization validation and bioburden limits permit ISO 8.
Nutraceutical, cosmetic and personal-care filling and packaging.
Grade D support areas: material staging, equipment wash, corridors around sterile suites.
Laboratories, pilot plants and cannabis post-processing where a demonstrable particle limit is wanted.

Where ISO 8 is more than you need

A controlled-not-classified (CNC) room provides filtered air, temperature and humidity control, cleanable finishes and gowning rules without an ISO class, particle certification or the recurring cost. For warehousing, secondary packaging, many quality control laboratories and pilot work, CNC is the honest specification. The test is whether any regulation, customer or validation assumes a particle limit; if none does, a classified room adds cost without adding control.

What it costs

ISO 8 is the least expensive classified room per square foot, and the one most often built inside an existing shell; our cleanroom cost guide gives current ranges by class. The recurring cost is annual certification and the HEPA filter replacement cycle, both lower than for ISO 7 because the filter count is lower.

How Paul Industries builds them

We build ISO 8 rooms as modular envelopes or as conversions of existing space, with the HVAC or fan-filter ceiling, pressure control, utilities and process connections in one scope, and we are direct about when a client’s process needs ISO 8, ISO 7, or a controlled-not-classified room instead.

Standards referenced: ISO 14644-1 · ISO 14644-2 · EU GMP Annex 1 (EudraLex Vol. 4) · USP 797 · 21 CFR 211 · 21 CFR 820 / QMSR · ISO 13485

Frequently asked questions

What is an ISO 8 cleanroom?

An ISO 8 cleanroom is a controlled room in which airborne particles do not exceed 3,520,000 per cubic meter at 0.5 micron and larger, 832,000 at 1 micron and 29,300 at 5 micron, in the occupancy state the specification names. It is the old Class 100,000, the least stringent classified cleanroom in common use, and the grade of ante-rooms, non-sterile pharmaceutical suites and much device and supplement manufacturing.

How many particles per cubic meter does ISO 8 allow?

3,520,000 particles per cubic meter at 0.5 micron and larger, with 832,000 at 1 micron and 29,300 at 5 micron. Every sampling location must meet the limit in the stated occupancy state; the count is not averaged across the room.

What is the ISO 8 cleanroom standard, and is it the same as Class 100,000?

The ISO 8 cleanroom standard is ISO 14644-1, which sets the particle limits, with ISO 14644-2 for monitoring and ISO 14644-4 for design; Class 100,000 is the older Federal Standard 209E designation, based on particles of 0.5 micron per cubic foot, and maps to ISO 8 under ISO 14644-1. FED-STD-209E was withdrawn in 2001, so new specifications should say ISO 8, but the older name persists on drawings and in procurement documents.

What does it take to move a room from ISO 8 to ISO 7 performance?

Roughly two to three times the air changes, a genuine pressure cascade with gowning airlocks, fuller gowning and a tighter envelope. ISO 8 can usually be built inside an existing shell on terminal HEPA filters; ISO 7 usually needs dedicated air handling, which is why the two classes are priced so differently despite being one step apart.

What is the difference between ISO 8 and ordinary room air?

Roughly one class. Typical indoor air in an office or warehouse runs around ISO 9, about 35 million particles per cubic meter at 0.5 micron, ten times the ISO 8 limit. That narrow margin is why ISO 8 is achievable with modest air handling and why door discipline and gowning matter so much to keeping it.

Can a building air handler serve an ISO 8 room?

Often, yes, which is one of the practical advantages of ISO 8. ISO 14644-1 does not set an air change rate; common design practice is 10 to 25 air changes per hour of HEPA-filtered supply, with published guidance ranging from about 5 to 48 depending on occupancy and process, and USP 797 requires at least 20 for an ISO 8 ante-room. The rate is confirmed by particle counting in the specified occupancy state, not assumed.

Does an ISO 8 room need an airlock?

Usually not on its own: a single door with a closer to unclassified space is common, and an airlock is added when the ISO 8 room serves an ISO 7 room, in which case the ISO 8 room is the airlock. Pressure is held positive to unclassified space, commonly at least 5 pascals, and negative to any ISO 7 room it serves so that the cascade steps down from the cleanest room outward, with 10 to 15 pascals between adjacent grades being the usual guidance figure. Containment applications such as non-sterile hazardous drug compounding hold the ISO 8 room negative instead.

Is Grade D the same as ISO 8?

Not quite: Grade D is ISO 8 at rest, with no in-operation particle limit defined in Annex 1. Grade C is ISO 8 in operation (and ISO 7 at rest). Grade D carries microbial limits of 200 CFU per cubic meter of air, 100 CFU per 4-hour settle plate and 50 CFU per contact plate; ISO 14644 itself sets no microbial limits.

What are the ISO 8 cleanroom gowning requirements?

ISO 8 cleanroom gowning requirements are the lightest of the classified grades: hair cover, beard cover where applicable, a low-linting frock or coverall, shoe covers or dedicated footwear, and gloves where the product requires them, put on in a gowning area with a bench or line. A full airlock is often not required for ISO 8 alone. For a Grade D pharmaceutical room Annex 1 expects hair and beard covering, a general protective suit and appropriate shoes.

Can fan-filter units alone make an ISO 8 room?

Yes, in many rooms. The class is achieved by HEPA-filtered supply air, usually H13 or H14 terminal filters in the ceiling or fan-filter units, each leak-tested in place at certification. What differs from ISO 7 is the number of filters and the air volume, not the filter grade.

What does an existing building need to host an ISO 8 room?

Ceiling height, structure and a return path, because ISO 8 is the class most often built inside an existing building. A modular envelope or a sealed, epoxy-finished room inside the existing shell, with a fan-filter ceiling or terminal HEPAs on the building air handler, low returns and a sealed envelope, will reach ISO 8 in most industrial buildings. The constraints are ceiling height for the plenum, structural support for the grid and a return air path that does not cross other spaces.

Is an ISO 8 cleanroom required for medical device manufacturing?

Not by regulation. The Quality Management System Regulation and ISO 13485 require the manufacturer to control the environment to the degree the product needs; the sterilization validation and its bioburden assumptions usually drive the choice. Sterile device assembly and packaging are commonly done in ISO 8, sometimes ISO 7, and non-sterile devices are often made in controlled-not-classified rooms.

Is an ISO 8 room required for non-sterile pharmaceutical manufacturing?

21 CFR 211 does not name a class for non-sterile products; it requires facilities that prevent contamination and mix-ups. Manufacturers commonly build oral solid dose, liquid and topical suites to ISO 8 (Grade D) as a defensible way of demonstrating that control, but the choice is the firm’s to justify, not a regulatory minimum.

What is the USP 797 requirement for an ISO 8 room?

USP 797 requires the ante-room to the sterile compounding buffer room to be ISO 8 with at least 20 air changes per hour, positive to the surrounding space, and separated from the ISO 7 buffer room by a line of demarcation or door. Where the ante-room opens into a negative-pressure buffer room, USP 797 requires it to be ISO 7 instead.

What tests are in an ISO 8 certification report?

Particle counts at the number of locations ISO 14644-1 derives from the floor area, each sample of at least 2 liters, in the specified occupancy state; installed HEPA filter leak testing; airflow volume and air change verification; and pressure differential measurement. Recovery time and smoke studies are rarely specified at ISO 8. The report must state the occupancy state and the resulting class.

Is annual recertification enough for an ISO 8 room?

ISO 14644-2 sets particle classification at a maximum interval of 12 months for ISO 6 and coarser classes, with airflow and pressure checked more frequently under the monitoring plan. GMP sites and USP 797 compounding facilities often certify every 6 months; annual is typical for device and supplement rooms.

Why is Grade D defined only at rest?

Because Annex 1 sets no in-operation particle limit for Grade D, leaving it to the manufacturer to justify. At rest means the room is complete with equipment running and no people; in operation means staff and process are active. Annex 1 Grade D is defined only at rest, which is why an ISO 8 specification for a GMP support room usually means at rest. If a customer or validation assumes ISO 8 in operation, the room must be designed and tested that way, which raises the air change rate.

When is a controlled-not-classified room better than ISO 8?

When no regulation, customer requirement or validation assumes a particle limit. A controlled-not-classified room gives filtered air, temperature and humidity control, cleanable finishes and gowning rules without particle certification or its recurring cost, and it is the honest specification for warehousing, secondary packaging, many QC laboratories and pilot work.

What makes one ISO 8 room cost more than another?

Ceiling height and structure, the return air path, whether the building air handler can serve the room, and the finishes. ISO 8 is the least expensive classified room per square foot and the one most often built inside an existing shell, with the lowest recurring certification and filter cost. Our cleanroom cost guide gives current per-square-foot ranges by class. The main cost drivers are ceiling height and structure, the return air path, and whether the building air handler can serve the room.

Can an ISO 8 room be upgraded to ISO 7 later?

Sometimes, if it was designed for it: the envelope must be tight enough for a larger pressure differential, the ceiling grid must have spare positions for more HEPA terminals, the air handler must have capacity for two to three times the air changes, and a gowning airlock must fit. Rooms built to the minimum for ISO 8 usually cannot be upgraded without rebuilding the mechanical system, so the decision belongs at the design stage.