FAQ - Airborne Particles

Question
Per ISO, statistical analysis is required if the number of locations to be measured are (as the area calculated) >2 and < 9. If, based on my area, the number of locations to be sampled are 7, can I perform counting at extra locations (up to 10) and avoid the statistical analysis?

Answer

The question is in respect to can I add sample points to remove the need for statistical compliance. The answer is yes, if you refer to section B.4.1.2 of the standard it allows additional points providing that they have been deemed additional due to a risk analysis. A document may need to be generated defining the size of the room to require 10 points, in your opinion, the best rational would be that the "room is turbulent and additional points are to determine full coverage". The 10 samples then need to be spaced equidistant and at work height.

There are changes proposed to ISO that would removed the 95% limits and so this philosophy is certainly in keeping with current process.

For additional information read our paper Particle Monitoring Requirements in Pharmaceutical Cleanrooms.