Cleanroom Classification

Cleanroom Classifications, Classes and ISO Standards

What is a Cleanroom?

A cleanroom is a room that has minimum pollutants such as airborne microbes, dust, aerosol particles and chemical vapors. The contamination level of the cleanroom is controlled and is specified by the number of particles per cubic meter (m³) at a specified size of the particle.

What is a Clean Zone?

A cleanroom is a defined area where the no.  concentration of particles is classified and controlled. It is designed to disallow or eliminate contaminants.

Use of Cleanroom

Cleanrooms are used in the manufacturing industry. It is used to control small particles that can hamper the manufacturing process.

Is Cleanroom really clean?

Do you know your normal office room has between 500000 and 1000000 particles per cubic foot?

And class A cleanroom has 100 particles per cubic foot.  The size and complexity of the cleanroom are different.

Clean room Air Flow Principles

Cleanrooms keep up without particulate air using either HEPA or ULPA filters employing laminar or turbulent airflow principles. Laminar, or unidirectional, air flow systems direct clean air horizontal or in a downward direction in a steady stream towards filters situated on walls close to the cleanroom floor or through raised punctured floorboards to be recirculated.

Laminar airflow systems are normally employed across 80 percent of a cleanroom roof to keep up steady air preparation. Stainless steel or other non-shedding products are used to make laminar airflow filters and hoods to forestall overabundance particles entering the air.

The harsh air tries to trap particles that might be noticeable all around and drive them towards the floor, where they enter channels and leave the cleanroom environment. US FDA and EU have set down rules and breaking point for microbial defilement which is tough to guarantee independence from microorganisms in drug items.

Requirement of a Cleanroom in Pharma Company

The cleanliness level of a pharmaceutical cleanroom depends on the product.  Non-sterile product require only proper ventilation and filtered air

But there is always a requirement of a sterile environment to manufacture products. Cleanrooms fulfill this requirement by reducing the contamination level.

Corridors in Pharmaceutical Cleanroom

Basically, there are two corridors required to keep pharmaceutical products free from risk.

Clean Corridors: Drugs which are in powdered form need to be free from microorganisms. And there is always a risk of cross-contamination between products.  So for the manufacturing of these drugs a negative (-ve) pressure is required to keep powdered drug free from contamination.

Dirty Corridors: There is a positive pressure in Cleanrooms for aspectics and biopharmaceuticals products manufacturing.

Notable Do’s and Don’ts in a Cleanroom


  • Always keep the doors of the cleanroom closed
  • Clean all surfaces regularly to remove contamination
  • Cleanroom staff must wear the suits


  • Don’t allow eatables and drinks inside the cleanroom
  • Bring in dirty material and equipment
  • Turn off the filters
  • No Smoking

Cleanroom Classifications

Cleanrooms are classified by the quality of the air. In FED STD 209 (A to D) of the United States of America, the no. of particles equal to and more than 0.5 μm is measured in one cubic foot of air and used for the cleanroom classification. This metric nomenclature is accepted in the latest 209E version of the Standard.  And TC 209 is the latest standard from the International Standards Organization.  Both standards classify a clean room by the no. of particles present in the lab air.  The cleanroom classification standards FS 209 E and ISO 14644-1 require measurements of specific particle count and calculations for the classification of cleanroom cleanliness level.

Cleanrooms are classified according to the no. and particle size allowed per volume of air. Large numbers such as class 100 or class 1000 refer to US FED STD 209E and denote the no. of particles of size 0.5 microns or larger size allowed per cubic foot of air.

United States FED STD 209E

                                              Maximum Particles/ft³
Class ≥0.1μm ≥0.2 μm ≥0.3 μm ≥ 0.4 μm ≥0.5 μm ISO equivalent
1 35 7 3 1 0.007 ISO 3
10 350 75 30 10 0.07 ISO 4
100       100 0.7 ISO 5
1000       1000 7 ISO 6
10,000       10000 70 ISO 7
1,00,000       100000 700 ISO 8

ISO 14644-1 Cleanroom Standards

  Maximum Particles/m³
ISO Class ≥0.1μm ≥0.2 μm ≥0.3 μm ≥ 0.5 μm ≥ 1 μm ≥ 5 μm US FED STD 209E Equivalent
1 10 2          
2 100 24 10 4      
 3 1000 237 102 35 8   Class 1
4 10,000 2370 1020 352 83   Class 10
 5 1,00,000 23700 10200 3520 832 29 Class 100
 6 10,00,000 237000 102000 35200 8320 293 Class 1000
7       352000 83200 2930 Class 10,000
 8       3520000 832000 29300 Class 1,00.000
Criteria Class 10/ISO Class  4 Class 100/ ISO Class 5 Class 1000/ ISO Class 6 Class 10000/ISO Class 7 Class 100000/ISO Class 8
Air Changes per hr/min 500 to 600/ 8 to 10 300 to 480/5 to 8 180/3 60/1 20/0.33
Filter Coverage percentage 90 to 100 60 to 70 20 to 30 7 to 15 4 to 5
CFM per sq. foot 85 to 90 36 to 65 18 to 32 9 to 16 4 to 8
Filter Efficiency 99.9997 percent ULPAs 99.997 percent HEPAs 99.997 percent HEPAs 99.997 percent HEPAs 99.997 percent HEPAs
Type of  Ceiling  T-bar grid  T-bar grid  T-bar grid Conventional T-bar grid Conventional T-bar grid
Light Fixture Tear drop or Flow Thru Tear drop or 2’ x 4’ clean room fixture 2’ x 4’ clean room fixture 2’ x 4’ clean room fixture 2’x4’ standard fixture
Ceiling Panel Fiberglass reinforced panels, Mylar or  Vinyl Rock Fiberglass reinforced panels , Vinyl Rock or Mylar  Mylar/ Vinyl Rock Mylar /Vinyl Rock Mylar/ Vinyl Rock
Wall Type Modular /Standard Built Modular/Standard Built Modular/ Standard Built Modular/Drywall Modular/Drywall
Floor Cover Epoxy or Welded sheet Vinyl Epoxy or Welded sheet Vinyl Epoxy  or Welded sheet Vinyl Sheet Vinyl/ Vinyl Composite Tile Sheet Vinyl /Vinyl Composite Tile
Floor Base 2”- 6” Cove Cove/Aluminium Base Channel Cove/Aluminium Base Channel Cove/Aluminium Base Channel Cove/Aluminium Base Channel
Air Returns Raised floor /Center returns Low wall on long axis Low wall at perimeter Low wall Low wall /ceiling

British Standard 5295 Cleanroom Standards

Class ≥0.5μm ≥1 μm ≥5 μm ≥ 10 μm ≥25 μm
1 3000   0 0 0
2 300000   2000 30  
3   1000000 20000 4000 300
4     20000 40000 4000

In the United Kingdom, BS 5295 is about to be replaced by British Standard EN ISO 14644-1

ISO Cleanrooms Specifications

ISO Class 1 is the cleanest cleanroom, mostly used in electronics and lifesciences industries that require nanotechnology or ultra-fine particulate processing. The recommended air changes per hour for an ISO Class 1 clean room are 500 to 700.

The recommended air changes for ISO Class 2 and ISO Class 3 are 500-750. And for ISO Class 4 it is 400-750 air changes per hour.

In Biotechnology and Pharma industry Cleanrooms are required for taking care of fluids, cells, organic substances, chemicals and compounds. Because outside sources can decrease the cell viability rates and lead to incorrect test results. So cleanrooms for these industries are mostly specified between ISO 5 and ISO 8

ISO 5 cleanroom has less than 3520 particles > 0.5 microns per cubic meter and 250-300 HEPA filtered air changes per hour. The equivalent Federal standard is class 100

 ISO 6 cleanroom specification is quite similar to ISO 5 but it has 180 HEPA filtered air change per hour basis. The equivalent federal standard is class 1000

ISO 7 is a common cleanroom specification. A cleanroom must have less than 352000 particles > 0.5 micron per cubic meter and 60 HEPA filtered air changes per hour. The equivalent federal standard is class 10.000 or 10000 particles per cubic foot.

ISO 8 is the least clean cleanroom classification. A cleanroom must have less than 35200000 particles > 0.5 micron per cubic meter and 20 HEPA filtered air change rate. The equivalent federal standard is class 100000 or 100000 particles per cubic foot.  

ISO Ceiling Fan Coverage Percentage Specifications

To achieve the optimal ACH (air change per hour) or ACR (air change rate) requires ceiling fan coverage. The cleanest cleanroom has FFUs (filter/fan units) in every 610-millimeter x 219-millimeter ceiling area. This is close to 100 percent coverage which provides a unidirectional flow of filtered air to eliminate contaminants.

This level of coverage not only leads to high energy consumption but also high construction and operation cost.

You may like to learn: Energy Saving in Cleanrooms

Below table represents the ceiling coverage percentage for each ISO class:

ISO Class Ceiling Coverage %
ISO 1 to 2 80 to 100 %
ISO 3 60 to 100 %
ISO 4 50 to 90 %
ISO 5 35 to 70 %
ISO 6 25 to 40 %
ISO 7 15 to 20 %
ISO 8 5 to 15 %

ISO 5 depends on laminar or unidirectional airflow. This means that filtered air is supplied in a uniform direction at a constant velocity.  Air is recirculated between base of the walls and the filtering system

ISO 6 or above ISO 6 cleanrooms rely on turbulent or non-unidirectional airflow.  It gives a uniform environment and does not allow the formation of air pockets.

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