Cleanroom classes and luminaires

The short answer

A cleanroom’s class sets how many airborne particles each cubic metre of air may hold. ISO 14644-1 defines classes from ISO 1 (cleanest) to ISO 9. Pharmaceutical sites in Europe also work to the EU GMP Annex 1 grades A to D, which set limits both “at rest” and “in operation”. A luminaire doesn’t make a room clean, but a poor one can stop it staying clean. Look for a luminaire that seals to the ceiling, has smooth faces with no dust traps, and can be cleaned and disinfected repeatedly. A class stated for a luminaire is the manufacturer’s design or test claim, so check what it means for your room.

ISO 14644-1 classes

ISO 14644-1:2015 classifies air by the number of particles at or above a given size per cubic metre. Each class step is a factor of ten. The table gives the limits for particles of 0.5 µm and larger, the size most often used to compare classes.

ISO class	Max. particles ≥ 0.5 µm per m³
ISO 1	Not specified at this size
ISO 2	4
ISO 3	35
ISO 4	352
ISO 5	3,520
ISO 6	35,200
ISO 7	352,000
ISO 8	3,520,000
ISO 9	35,200,000

The standard also sets limits at other sizes, from 0.1 µm to 5 µm. ISO 1 to ISO 4 are mostly found in semiconductor and other microelectronics work. ISO 5 to ISO 8 cover most pharmaceutical, medical device and hospital clean areas. ISO 9 is close to normal room air, but with controlled filtration.

You’ll still hear the older US Federal Standard 209E names, such as “Class 100”. Roughly, Class 100 corresponds to ISO 5, Class 10,000 to ISO 7 and Class 100,000 to ISO 8. FS 209E was withdrawn in 2001, so specify by ISO class.

EU GMP Annex 1 grades

EU GMP Annex 1 covers the manufacture of sterile medicinal products. Its 2022 revision applies from 25 August 2023. It uses four grades, with separate limits for a room at rest (installed and running, but with no production and no people) and in operation.

Grade	Max. particles ≥ 0.5 µm per m³ at rest	In operation	Rough ISO equivalent (at rest / in operation)
A	3,520	3,520	ISO 5 / ISO 5
B	3,520	352,000	ISO 5 / ISO 7
C	352,000	3,520,000	ISO 7 / ISO 8
D	3,520,000	Set by the manufacturer from a risk assessment	ISO 8 / not predetermined

Grade A is the critical zone for high-risk operations such as aseptic filling, usually under unidirectional airflow. Grade B is the background room around it. Grades C and D are for less critical stages. The ISO equivalents are based only on the 0.5 µm particle limits. Annex 1 also sets microbial limits and other requirements that ISO 14644-1 doesn’t cover.

What makes a luminaire suitable

Annex 1 asks for exposed surfaces in cleanrooms to be smooth, impervious and unbroken, with no recesses that are hard to clean, and for ceilings to be sealed against the space above. A luminaire is part of that ceiling. In practice that means:

• A sealed joint to the ceiling. A gasket between the luminaire frame and the ceiling stops unfiltered air from the void being drawn into the room, or room air leaking out. In positively pressurised rooms, air will find any gap.
• A sealed optical chamber. The diffuser should be sealed to the body, so particles can’t collect inside and fall out later.
• Smooth, flush faces. Frameless (flush) designs, with no visible fixings between diffuser and body, leave fewer edges and corners for particles and cleaning residue. Framed designs can also suit, but check the joints.
• No dust traps. Avoid exposed screw heads, louvres, open slots and ledges on the room side.
• Materials that don’t shed and that tolerate your cleaning and disinfecting agents. See materials and cleaning.
• Gaskets that seal from the room side. Where luminaires are fitted from below, the gasket should be compressed against the ceiling as the luminaire is fixed, so the seal doesn’t depend on someone working in the void.

The room-side IP rating gives a useful indication of sealing. See IP ratings and sealing.

Why a luminaire’s stated class needs checking

You’ll often see luminaires described as “for ISO 5–6” or “for ISO 3–4”. Treat this as a claim to check, not a certificate:

• Cleanroom classes apply to rooms, not products. A room is classified by measuring its air. No luminaire is “ISO 5” on its own.
• A stated class reflects the design, such as how the luminaire is sealed and what it is made of. It may also be backed by tests, for example particle emission or leak tests. Ask what was tested, how, and by whom.
• Installation matters as much as design. A well-sealed luminaire in a badly cut or unsealed ceiling opening won’t protect the room.
• Your validation team decides. In GMP areas, the luminaire becomes part of the qualified installation, so the user’s quality and validation people need the data to support their own assessment.

We quote the class the manufacturer states for each product and say where it comes from. We can send the supporting documents we have, and tell you clearly where something hasn’t been tested.

How we can help

Tell us the class or grade of each room, the ceiling system and the cleaning regime, and we’ll suggest suitable luminaires and send the data your validation team will ask for. Start a project.

Sources: ISO 14644-1:2015, Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration; EudraLex Volume 4, EU GMP Annex 1, Manufacture of Sterile Medicinal Products (2022).