Timing the air filters

In our company we are trying to do a study to determine how often should we change the AC filter on the airhandlers that supply the HEPA filters. The idea we have is to periodically take the differential pressure across the filter and the air velocity right infront of the filter to see how the filters clogs with the time, and then anylize the data to reach some conclussions. That is just thinking with the evailable resourses I have right now. Some drawbacks with this idea is that I dont have any standard to refer to, or anything to actually see what going thourgh the filter. Anyone have a better idea? or there is any method already implemented that I can use? Thanks for any coolaboration you can make :)!

G4 air filters in processing rooms are changed after each batch and/or product change over. in non processing grey areas, the frequency is less and can be changed twice weekly or weekly as per the particle load, air change rate and pressure difference

Yes, in the production areas the air filters are change everytime there is a product change over, so those are change very frequently. But in other cases the the air hadler return does not take the air from the production area. Is there any standards or specifications to determine this?

there is no as such guideline or specification to my knowledge for the change of terminal return filters in AHU. but keep in mind that the more the frequency of changing the pre-filter, the less will be the load to the bag filter or fine filter which is non washable. this saves the life of bag filter and automatically the life of HEPA which is more costlier as compared to the return pre filters and bag filter (fine filter).

if the AHU has supply of fresh air, the air must be filtered through G4 coarse filter before it is subjected to fine filter. depending upon the nature of environment of your premises, 2-3 layers of G4 filters has to be used that saves non washable filters in AHU