Cleanrooms are designed, constructed, and operated in such a manner to control the introduction, generation, and retention of particles inside the enclosure. 

This is achieved by;

• Maintaining a positive pressure.
• Material selection for the structure and the equipment inside. 
• The PPE of any personnel 
• Filtration and dilution. 

The required classification of the cleanroom will depend on the process to be performed inside the room. Although the ISO 14644 series and FS209E and GMP classifications all stipulate a number of particles permitted at varying sizes, the question to ask when deciding which class you require is what size of particle will cause a problem to my process. 

Cleanroom validations are performed in 3 different states

As built. Usually, the cleanroom will have been newly built and has not been populated with any equipment. An empty room.

At rest. This is when the equipment has been installed but the room is not operating. This test can be performed throughout the life of the cleanroom. 

Operational. The cleanroom is functioning with the defined number of personnel and it is working in accordance with the defined process. This test is vital and should be performed throughout the life of the cleanroom.

The validation is ordered in these stages so that any problems can be identified before adding more variables. The cleanroom needs to be maintained to ensure it remains compliant.

How often should your cleanroom be validated? 

To keep your ISO 14644 status, cleanroom validation must be done every year, every 12 months. This is for ISO 5 now as well as 6,7 and 8. 

However, monitoring of the cleanroom should be done regularly but it will depend on your industry and your end client as to the frequency.