Definition of Cleanroom, explanation, types as per USA and other countries

1. CLEAN ROOM CLASSIFICATION
• Cleanrooms are classified according to the number and size of particles permitted per
volume of air.
• Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA
filters employing laminar or turbulent air flow principles.
• Laminar, or unidirectional, air flow systems direct filtered air downward in a
constant stream.
• Laminar air flow systems are typically employed across 100% of the ceiling to
maintain constant, unidirectional flow.
• Clean rooms are classified considering the particle size ≥ 0.5 microns per m3 or ft3.
• Major cleanroom standards are:
• United States: FED STD 209E: Federal Standard 209E
• United Kingdom: British Standards BS 5295
• International Organization for Standardization: ISO 14644-1
• Europe: European Union Standard (European Economic Commission
(EEC))

2. Grade At Rest >0.5
um/M3
At Rest
>5um/M3
Operational
>0.5um/M3
Operational
>0.5um/M3
A 3520 20 3520 20
B 3520 29 352,000 2900
C 352,000 2900 3,520,000 29,000
D 3,520,000 29,000 Not defined Not defined
Clean room classification : As per
FED STD 209E (Class) EEC (Grade)
100 A
1000 B
10,000 C
100,000 D
Meaning:
For a Class 100,000 area (1 Lakh), for particle size range 0.5 to <5 microns, maximum
particle count must not exceed 100,000 particles per ft3 OR 3,530,000 particles per m3.
At Rest – No personnel in clean room and all equipment are idle. Thus, dispersion of air
borne particles is about nill.
In Operation – Running equipment with personnel presence.