Environmental classification( air handling units)


The environment can impact the quality of a pharma­ceutical product differently at each manufacturing step. Certainly, the most critical environment is the one in which sterile products or components (vials, ampoules, stoppers, and such) are directly exposed. This is true for all aseptic-processing operations.

To link the environmental needs for every phase of the process, the critical environments are classified. These classifications follow diverse sets of criteria that are linked either to room airborne cleanliness levels, use of the environment, containment or segregation levels, and the like

Defining parameters used for classification include particles of a specific size per unit volume of air, microbial levels, and type of microorganisms (biohazard). The designation or nomenclature changes within industries and among countries. These classifications are set as part of standards or guidelines prepared by national health authorities such as the U.S. FDA, EMEA and other govern­mental institutions (e.g., U.S. National Institutes of Health), professional associations (e.g., PDA, IES) and ISO. In addition, many corporations have internal stan­dards and guidelines that apply to all of their associated companies.

FDA Guidance for Industry Sterile Drug Products Produced by Aseptic Processing Guideline

Critical Environments       

A critical area is one in which the sterilized drug product, containers, and closures are exposed to environ­mental conditions that must be designed to maintain product sterility CFR 21 [section 211.42(c)(10)]. Acti­vities conducted in such areas include manipulations (e.g., aseptic connections, sterile ingredient additions) of sterile materials prior to and during filling and closing operations.

Supporting Areas

Supporting clean areas can have various classifications and functions. Many support areas function as zones in which non sterile components, formulated products, in-process materials, equipment, and container/closures are prepared, held or transferred. These environments are soundly designed when they minimize the level of particle contaminants in the final product and control the microbiological content (bioburden) of articles and components that are subsequently sterilized.

The nature of the activities conducted in a supporting clean area determines its classification. FDA recommends that the area immediately adjacent to the aseptic processing line meet, at a minimum, Class 10,000 (ISO 7) standards under dynamic conditions. Manufac­turers can also classify this area as Class 1,000 (ISO 6) or maintain the entire aseptic filling room at Class 100 (ISO 5). An area classified at a Class 100,000 (ISO 8) air cleanliness level is appropriate for less critical activities (e.g., equipment cleaning).

Area Classifications and/or Cleanliness: Class Requirements Indicated in the September2004 FDA Guidelines

Clean area classification( 0.5 nm particles per ft2)2

ISO designation

  • 0.5 nm particles per m2

Microbiological active air action levels( cfu per m2)

Microbiological settling plates action levels (cfu per 4 hrs)





















a All classifications based on data measured in the vicinity of exposed

All classifications based on data measured in the vicinity of exposed

materials/articles during periods of activity. b ISO 14644-1 designations provide uniform particle concentration values for Cleanrooms in multiple industries. An ISO five particle concentration is equal to Class 100 and approximately equals EU Grade A. c Values represent recommended levels of environmental quality. You may find it appropriate to establish alternate microbiological action levels due to the nature of the operation or method of analysis. d The additional use of settling plates is optional.

e Samples from Class 100 (ISO 5) environments should normally yield no microbiological contaminants.

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