APC tests

[MedicineEng]

Dear All:
In my company as in all pharma sites, we have a Air Particle Counting monitoring program. For some time we are having some failures in rooms that puzzled me and consumed a great deal of my time (and company's money) trying to solve it. Recently, when again we were discussing this problem, a colleague of mine that is very experienced in this field, said a thing that surprised me:
She said that different brands of particle counters would give very different results in the particle counting. And we had that experience when we asked a subcontractor to makehte APC for us and its results were several times different than our own.
What I would like to ask is:
1-Did anybody experienced the same thing before?
2-how can we make engineering modifications based in results that are different depending on the machine that reads the APC?

Thanks a lot for you help.
PR

 

[quark]

Yeah, that happens always. With high sampling rate equipment, the results may not be much accurate. It also depends upon the quantity of air sampled each time.

Generally you need not bother as long as the particle counters pass your area classification(though they show substantial difference in readings). Better is to follow the 14644 guidelines for sampling rate, sampling time and minimum no. of detectable particles.

Is your area failing with 0.5 micron particles are with bigger ones?

 

[MedicineEng]

Thanks for the tip.
The particle is failing most on 0.5um but sometimes also fail bigger.
You say that it happens (the different result with different machines), but for me it is very difficult to understand that since big decisions are made over possible wrong data, like false results over the limit.

 

[quark]

Actually I had to depute three agencies to get reasonable result in one of our facilities. Ironically, all the agencies have calibrated particle counters with them.

There are many variables involved in this process. Particles are not sperical always and these particle counters approximate them to the nearest diameter depending on the calculation fed into them. Even fibres and microorganism are approximated as particles. Water droplets also add difficulty to this process. It also depends upon the locations where you take particle count.

Check for particles at HEPA outlet to get some confidence about the counter. LAF stations are better places to check efficiency of the particle counters. If your areas are failing with big particles then clean the areas thoroughly. Check for dead pockets(particularly farthest points from the risers).

Good luck,

 

[christyi]

Hello, I just experienced this occurrance this week. I am somewhat new to environmental monitoring, but we were testing a softwall enclosure and it kept failing at like 140,000 0.5micron particles / ft3 when only a couple months before we got numbers less than 20,000 with 2 different instruments! Then we had a contractor come in and test the exact same location, similar conditions, etc. and his calibrated instrument got ~15,000 when my calibrated instrument still got over 100,000. I just talked to the instrument tech and he said my particlar instrument had a +/-50% counting accuracy and +/-20% sizing accuracy. He said two of the exact same instruments in the exact same location, etc. could still be up to ~ +/-30% different in results! I think I will still send my instrument in to be evaluated by the manufacturer just to check its calibration status, but so far it seems like we have to deal with these inaccuracies. I know what you mean about making important decisions based on these numbers. I would like to look into this more, will try to let you know if I get a chance to find anything else out. Please let me know if you do too.