How can Select Particle count location?

How can select Particle count location? i know critical location. but How can select critical location?

Our HEPA filter particle size 0.3micron, while during Particle count monitoring, why we are selected 0.5micron, and 5micron particles, as per ISO guidelines 0.1micron, 0.2micron, 0.3micron also available.

Why we using 95% Upper confidence limit? What is Limit 95% Upper confidential

Please post any guidelines regarding this?

Regards//Sivakumar A

Key points in P/iCS annex -1

• [b]Grade A environments should be classified as ISO14644 class 4.8, not class 5. This is based upon the 5 micron particle limit of 20 (though why 20 was chosen instead of 29 is unclear).

• Central particle counters with long tube lengths will no longer be acceptable for clean room classification as they absorb too many particles – especially 5 micron particles. Similarly, the use of such particle counting systems for routine monitoring is discouraged.

• In critical areas with exposed product, continuous monitoring covering the duration of the operations is expected. Manifoldsystems might not be suitable for Grade A zone monitoring due to a lack of responsiveness. It is also important that monitoring in Grade A covers equipment assembly.[/b]

• Continuous monitoring is expected in Grade B zones while “not fully integral” containers are handled (e.g. partially stoppered or uncapped vials). Again, manifold systems might not be suitable due to a lack in responsiveness.

• Any microorganism isolated from a Grade A zone should result in a thorough investigation. The organisms must be identified and impact on batch release should be considered.

• All microbiological sampling methods for which guidance figures are quoted in the Annex should be used for routine monitoring. If any methods are not used, a justification is required.

• If product sterilisation is achieved using two filters in series,bioburden samples must be taken immediately before the final filter unless the second filter is simply used as security in case one of the two filters fails, in which case the sample can be taken before the first filter in series.