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Short answer
A clean room lab is a laboratory or production space whose air is filtered and monitored so that airborne particles stay under a stated limit for its classification. The classification is not a label on the door: regulators measure it near exposed materials, require it to be maintained by pressure and airflow control, and require it to be requalified on a schedule.
Definition and scope
In regulator guidance, a cleanroom is described by what it must hold, not by how it looks. The FDA’s 2004 guidance on aseptic processing states that ISO 14644-1 designations give uniform particle concentration values for cleanrooms in multiple industries, and that all classifications are based on data measured in the vicinity of exposed materials or articles during periods of activity. The European Commission’s EU GMP Annex 1 (2022) likewise sets limits for two states, at rest and in operation.
That makes a clean room lab a controlled state rather than a type of room. A bench-scale clean workstation with unidirectional airflow is a different piece of equipment from a classified room; for that, see what a laminar flow hood is. For the particle-count table across all nine ISO classes, see cleanroom classifications under ISO 14644-1; this page instead compares what two regulators expect of a classified space.
How a clean room lab is used in practice
Three controls recur in both documents.
Filtered, directional air
The FDA guidance describes the critical area, where sterilized product, containers and closures are exposed, as supplied with HEPA-filtered air at a velocity sufficient to sweep particles away and maintain unidirectional airflow. It states that an intact HEPA filter should be capable of retaining at least 99.97 percent of particulates greater than 0.3 micrometres, and it treats leak testing as distinct from efficiency testing. For certification practice, see HEPA filter certification.
Pressure between rooms
The FDA guidance says a positive pressure differential of at least 10-15 pascals should be maintained between adjacent rooms of differing classification with doors closed, and at least 12.5 pascals against an unclassified adjacent room. EU GMP Annex 1 gives a guidance value of a minimum of 10 pascals between adjacent rooms of different grades, with continuous monitoring of the differences for grade B.
Air change rate
For ISO 8 (Class 100,000) supporting rooms, the FDA says airflow sufficient for at least 20 air changes per hour is typically acceptable, and that significantly higher rates are normally needed for ISO 7 and ISO 5 areas. See air changes per hour for how the figure is calculated.
Classes and grades compared
The table sets the FDA’s air classifications beside the EU grades, using only the particle limits those two documents print (particles of 0.5 micrometres and larger per cubic metre).
| FDA class | ISO class | FDA limit (in activity) | EU grade | EU limit at rest / in operation |
|---|---|---|---|---|
| Class 100 | ISO 5 | 3,520 | A | 3,520 / 3,520 |
| Class 1,000 | ISO 6 | 35,200 | – | – |
| Class 10,000 | ISO 7 | 352,000 | B | 3,520 / 352,000 |
| Class 100,000 | ISO 8 | 3,520,000 | C | 352,000 / 3,520,000 |
| – | – | – | D | 3,520,000 / not predetermined |
The FDA’s footnote says an ISO 5 concentration equals Class 100 and approximately equals EU Grade A. The pairing of FDA ISO 7 with EU grade B and ISO 8 with grade C in the table is by matching particle limits, not a statement either document makes. Particles are only part of the picture: the FDA also lists active-air limits of 1, 7, 10 and 100 colony-forming units per cubic metre for ISO 5, 6, 7 and 8 respectively.
Where it matters for labs, clinics and supply decisions
The FDA guidance says a supporting area next to an aseptic line should be at a minimum ISO 7 under dynamic conditions, and that ISO 8 is appropriate for less critical activities such as equipment cleaning. Annex 1 sets a requalification interval of a maximum of 6 months for grade A and B areas and 12 months for grade C and D. These are the points to carry into a facility’s own procedures: what grade each activity needs, how often the room is requalified, and who monitors pressure between rooms. Operating discipline for people and materials is covered in cleanroom gowning and the cleanroom checklist.
Common misunderstandings
A cleanroom is a room with a rating
Both documents tie the rating to measurements taken during use and to periodic requalification, so the rating describes a maintained state.
ISO 5, Class 100 and Grade A are interchangeable
The FDA calls ISO 5 equal to Class 100 and only approximately equal to EU Grade A. The EU grade also carries operational conditions: grade A is the critical zone for high-risk operations and normally uses localised unidirectional airflow in restricted access barrier systems or isolators.
One pressure number applies everywhere
The FDA states 10-15 pascals between rooms of differing classification; Annex 1 gives 10 pascals as a minimum guidance value. Follow the document that governs your product and market.
These rules apply to every lab
Both documents govern sterile drug manufacturing. Research laboratories can use them as reference points, but they are not a universal laboratory rule set.
FAQ
What is a clean room lab?
A lab whose air cleanliness is controlled and monitored to a stated particle limit, with filtered air, room-to-room pressure control and periodic requalification.
How often is a clean room requalified?
Under EU GMP Annex 1, the maximum interval is 6 months for grade A and B areas and 12 months for grade C and D.
Is a clean bench the same as a clean room?
No. A clean bench is a localised workstation; a clean room is a classified space. See the laminar flow hood guide linked above.
Sources
- U.S. Food and Drug Administration, Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing – Current Good Manufacturing Practice (September 2004), checked 2026-10-29.
- European Commission, EU GMP Volume 4, Annex 1: Manufacture of Sterile Medicinal Products, C(2022) 5938 final (22 August 2022), checked 2026-10-29.
