This is a very helpful discussion as our auditor inquired about our CA testing this time. We are BRC with a low moisture product and the BRC Standard says we need to MONITOR the Air. We do check and change our filters regularly and can prove it.
Just as having your in-house Lab certified or sending all testing out to a 3P lab keeps getting pushed upon us, this CA testing keeps coming up as well.
I found this information from Parker who makes the CAMTU tester mentioned above- part of a series- Enjoy! 
http://blog.parker.c...des-part-1-of-6