An overview of ISO 14644 clean room classification

Introduction:

Clean room is the one in which concentration of airborne particles can be classified and controlled and designed in a way to control release, retention and generation of particles in the room.  ISO is International Organisation for standardization and is a federation worldwide for national standards. ISO 14644 classifies the cleanliness of air as the airborne particles concentration in cleaner rooms and zones. 

• Airborne particle cleanliness classes

  CLASS	Number of particles per cubic meter by micrometer size
  	0.1 micron	0.2 micron	0.3 micron	0.5 micron	1 micron	5 micron
  ISO 1	10	2
  ISO 2	100	24	10	4
  ISO 3	1000	237	102	35	8
  ISO 4	10000	2370	1020	352	83
  ISO 5	100000	23700	10200	3520	832	29
  ISO 6	1000000	237000	102000	35200	8320	293
  ISO 7				352000	83200	2930
  ISO 8				3520000	832000	29300
  ISO 9				35200000	8320000	293000

• Below is the list of standard documents for a cleanroom

• ISO Document	Title
  ISO 14644-1	Classification of Air cleanliness
  ISO 14644-2	Cleanroom testing for compliance
  ISO 14644-3	Methods for evaluating and measuring cleanrooms and associated controlled environments
  ISO 14644-4	Cleanroom design and construction
  ISO 14644-5	Cleanroom operations
  ISO 14644-6	Terms, definitions and units
  ISO 14644-7	Enhanced clean devices
  ISO 14644-8	Molecular contamination

Classification number:

Number of particles for any class is calculated for particles of any size by using the formula

                                    C_n = 10^N X (0.1/D)^2.08

C_n = maximum permitted concentration (particle/m³ of air) of airborne particles which are equal to or larger than the considered particle size, rounded to nearest whole number

N = ISO classification number (should not be more than 9).

D = particle size (µm)

0.1 = constant (µm)

Other considerations:

Another crucial factor to be considered is air change per hour or air change rate which determines number of times the air filtered per hour is substituted by existing volume in the chamber. In a cleanroom air change occurs from 10 to 600 times per hour.

Fan generated air speed indicates that more velocity of airflow helps in maintaining a cleaner room.

Clean rooms should also maintain positive pressure which helps in preventing unclean air from outside. Between spaces air pressure of 0.03 - 0.05 inches water gauge is required.

Laminar turbulent air flow is recommended as it provides consistent environment and eliminates air pockets in a place if contaminants may congregate.

Clean room, classification number, airborne, particles, laminar turbulent air

• cleanrooms and associated controlled environments. international standard. iso 14644. http://drug.fda.moph.go.th/drug/zone_gmp/files/gmp2549_2/aug2106/7.iso14644.pdf. accessed may 17, 2016.
• fs209e and is0 cleanroom standards. terra universal critical environmental solutions. https://www.terrauniversal.com/cleanrooms/iso-classification-cleanroom-standards.php accessed may 17, 2016.
• cleanrooms and associated controlled environments -- part 1: classification of air cleanliness by particle concentration. iso 14644-1:2015. iso. http://www.iso.org/iso/catalogue_detail?csnumber=53394. published december 12, 2015. accessed may 17, 2016.