The same room can be called ISO 7 by the engineer who certified it, Grade C by the QA lead who wrote its monitoring plan and something else entirely by a colleague who came over from a food plant. All three are using the right word in their own framework. The trouble starts when a team assumes they mean the same thing.
ISO 14644-1 classifies cleanrooms by airborne particle concentration. EU GMP Annex 1 defines Grades A to D for sterile manufacturing and covers both viable and non-viable monitoring, using ISO classes for its particle limits. Food plants typically use four hygienic zones instead. Each framework answers a different question, so record both the scheme and the class on every monitoring area.
This is an overview, not regulatory advice. Work from the current text of the guidance and your own contamination control strategy.
What does ISO 14644-1 classify?
ISO 14644-1 classifies cleanrooms by how many airborne particles they contain at given sizes, from ISO 1, the cleanest, down to ISO 9. It sets out how many locations to test and how to decide whether a room meets its class.
Two things are easy to forget. First, it's a classification standard. It tells you a room met its class on the day it was tested, usually at qualification or requalification. Ongoing monitoring is covered separately, in ISO 14644-2. Second, it's only about particles. It has nothing to say about microorganisms, surfaces or the people working in the room.
How do EU GMP Annex 1 grades relate to ISO classes?
EU GMP Annex 1 covers the manufacture of sterile medicinal products. The current version, in force since August 2023, asks manufacturers to build monitoring inside a contamination control strategy, so that where and how often they sample follows from a documented view of risk.
It uses four grades. Grade A is the critical zone for things like aseptic filling. Grade B surrounds it in aseptic processing. Grades C and D cover less critical stages. Unlike ISO 14644-1, Annex 1 deals with viable as well as non-viable monitoring, and it treats a room at rest and in operation as two different conditions.
For particle limits, Annex 1 borrows ISO's classes. Grade A is ISO 5 both at rest and in operation. Grade B is ISO 5 at rest and ISO 7 in operation. Grade C is ISO 7 at rest and ISO 8 in operation. Grade D is ISO 8 at rest, with the in-operation limit left to the manufacturer.
So a sterile suite often carries two labels at once, and that's fine. The ISO certificate shows the room met its class when tested. The Annex 1 monitoring program shows whether it keeps performing day to day, with people, materials and interventions in it. One doesn't stand in for the other. For more on validation and compliance in sterile and GMP environments, see GxP compliance at Uncountable.
How do food plants classify monitoring areas?
Food and beverage plants rarely use particle classes at all. Monitoring programs there, especially those looking for Listeria in ready-to-eat production, usually divide the plant into four hygienic zones. Zone 1 is anything that touches food, like slicer blades and conveyor belts. Zone 2 is right next to it: equipment frames, control panels. Zone 3 is the rest of the processing area, including floors, drains and walls. Zone 4 is everywhere further away, such as corridors, locker rooms and loading docks. Many plants also draw a hard line between raw and ready-to-eat areas and treat that boundary as a control point in its own right.
The logic is familiar to anyone from a cleanroom background, just with different vocabulary. The closer you get to the product, the more you sample and the faster you respond. A positive on a floor drain means look harder nearby. A positive on a contact surface may mean product is affected.
Writing it down so it stays useful
Whichever framework applies, record two things on each room or area: the scheme and the class within it. "EU GMP grade, Grade C." "Hygienic zone, zone 2." That lets a sterile suite and a food plant share one monitoring system without forcing them into the same language, and it lets results be compared fairly across sites that use the same scheme. Classification is also the starting point when designing a monitoring plan.
Classifications also change, and that needs care. When a room is regraded, the results taken before the change were judged against the old classification. Before relying on any system for trend review, check whether you can still see what applied to an older result.
In Uncountable, each monitoring area holds a classification scheme and class next to its site map, whether that's an EU GMP grade, an ISO class or a hygienic zone.
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