What Is an ISO 5 Cleanroom?

An ISO 5 cleanroom is a room or zone whose air contains no more than 3,520 particles of 0.5 µm or larger per cubic meter, measured to ISO 14644-1. It sits two classes cleaner than the ISO 7 rooms common in electronics assembly, which means a hundred times fewer particles, and it is the cleanest class most pharmaceutical and medical work uses.

ISO 14644-1 sets limits at several particle sizes, and a room can be classified at one or more of them. The table shows the ISO 5 limits beside ISO 7 for comparison.

Older documents give ISO 5 a limit of 29 particles at 5 µm. The 2015 edition of ISO 14644-1 removed it, because counts that low cannot be sampled reliably. Under the withdrawn US Federal Standard 209E, ISO 5 was Class 100: no more than 100 particles of 0.5 µm per cubic foot.

People and processes shed particles all the time, so an ISO 5 zone relies on sweeping them away faster than they build up. Most achieve it with unidirectional airflow, often called laminar flow: HEPA-filtered air flows down or across the work zone in parallel streams at an even speed, carrying particles away from the product instead of mixing them around the room. Guidance has long pointed to an air speed of around 0.45 m/s at the working height, although the right figure depends on the process and is proven by testing rather than fixed by the standard.

Whole rooms at ISO 5 are expensive, because the filtered air supply has to cover most of the ceiling. Many sites instead create an ISO 5 zone only where the product is exposed, inside a cleaner background room.

ISO 5 is a particle class only. Regulated industries add their own rules on top of it.

In Europe and the USA, sterile medicines are made under EU GMP Annex 1. Its Grade A, the zone for open product and aseptic connections, must meet ISO 5 both at rest and in operation, and Grade B, the background to Grade A, must meet ISO 5 at rest. Annex 1 also sets microbial limits and expects continuous particle monitoring in Grade A, neither of which ISO 14644-1 covers. In the United States, USP 797 requires sterile preparations to be compounded inside an ISO 5 primary engineering control, such as a laminar airflow workbench or a compounding isolator, normally placed in an ISO 7 buffer room. Our explainer on the ISO 7 cleanroom covers that background class.

Classification follows ISO 14644-1. The number of sampling locations comes from a table in the standard based on the floor area, and at each location a particle counter must sample enough air to expect at least 20 particles at the class limit. At 0.5 µm for ISO 5 that works out at around 5.7 liters per location, with a minimum of 2 liters and one minute. A room passes when every location is within the limit.

The test can be run in three states, so a certificate should say which one applies: as built (empty), at rest (equipment installed and running, no people) and in operation (normal working). ISO 14644-2 then sets out a monitoring plan to show the room stays in class, and most sites repeat the classification at least once a year. Pharmaceutical Grade A zones also need airflow visualization, usually smoke studies, to prove the flow sweeps the critical area.

Anything placed inside an ISO 5 zone can shed particles or disturb the airflow, so equipment is kept to a minimum. Computers and screens are usually mounted flush in a wall or behind a window, with the electronics outside the clean zone, and operators use them through gloves. Where a screen does sit in or beside the zone, it should be fanless, fully sealed and smooth, so it adds no particles and survives repeated wiping with sporicidal and alcohol-based agents.

Our guide to clean room computers sets out what to specify for each cleanroom class. For screens near ISO 5 work, our stainless steel panel PCs and fully sealed IP65 panel PCs provide the flat fronts and fanless cooling that cleaning procedures expect.

We supply fanless, sealed panel PCs and displays for cleanroom work as part of a complete system, with the mounting and finish matched to the room class and cleaning regime as standard.