Air Volume required (Sampling) during non viable particulate count in different area

Dear Sir,

here i am keen to know that during NVP monitoring by a particle counter how much air is required for sampling a location.
is different air volume required for different grade of area.
kindly provide guidance at same.

Dear sir,

for each cleanliness class it’s required a minimum sample volume (in litres) per locaion which is calculated by the following formula:

Vs = (20 / Cn,m) x 1000

where Cn,m is the class limit (number of particles per cubic metre) for the largest considered particle size specified for the relevant class.
Vs is the single sample volume per location (liters)

For more details, have a look at ISO 14644 part 1