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All Good Manufacturing Practice (GMP) questions

Question 13 of 20 Fundamentals Concept

What are cleanroom grades A to D in EU GMP Annex 1?

Short answer

Grade A is the critical zone where sterile product or surfaces are exposed, such as the filling zone. Grade B is the background for grade A in conventional aseptic rooms. Grades C and D are for less critical steps or as isolator backgrounds. Each has particle and microbial limits at rest and in operation.

Why

Annex 1, revised in 2022, sets four grades so that the cleanest air protects the most exposed product. Grade A is normally provided by unidirectional airflow inside a RABS or isolator, and direct operator intervention into it should be minimized. Grade B surrounds grade A in a conventional aseptic suite, while lower grades can be justified around isolators.

Grades C and D host less critical steps such as preparing solutions to be filtered, or filling products that are terminally sterilized. For classification, the limits are counts of particles at least 0.5 µm per cubic meter. Grade A allows 3,520 both at rest and in operation.

Grade B allows 3,520 at rest and 352,000 in operation, and grade C allows 352,000 at rest and 3,520,000 in operation. Grade D allows 3,520,000 at rest, and its in-operation limit is set by the manufacturer from risk and data. Viable limits follow the same logic.

Grade A expects no growth, and any growth there should be investigated. Grade B air has an action limit of 10 CFU per cubic meter. The grade is only the starting point.

Annex 1 lets action limits be tighter based on trends, process or the contamination control strategy, and a room that meets its numbers can still be poorly controlled if interventions and gowning are weak.

A strong answer covers

  • Grade A as the critical zone with unidirectional airflow
  • Grade B as background to grade A, C and D for less critical steps
  • At rest versus in operation limits
  • Grade A expects no viable growth
  • Limits can be tightened by the contamination control strategy

Common mistakes

  • Thinking grade A has a looser in-operation particle limit than at rest, when both are 3,520 per cubic meter.
  • Assuming any grade A colony is acceptable if it is below a numeric limit.
  • Treating ISO 14644 classification as the same thing as Annex 1 monitoring limits.