Air monitoring, clearance, and recordkeeping
What this domain tests
Sampling strategy, the difference between PCM and TEM, clearance criteria, and retention periods for records.
Air monitoring
- Personal sampling uses a battery pump at 0.5–5 L/min with a 25-mm, 0.8-µm mixed-cellulose ester filter in a conductive cassette, analyzed by PCM (NIOSH 7400). PCM counts fibers over 5 µm with a 3:1 aspect ratio but cannot distinguish asbestos from other fibers.
- Submit field blanks, roughly 10% of samples, and maintain chain-of-custody. Report f/cm³ for the sampled period, then compute the 8-hour TWA.
- TEM identifies fiber type and is used where PCM is ambiguous or a stricter clearance standard applies.
Clearance
- Sequence: containment still under negative pressure, visual inspection passed, aggressive sampling with air movers run before and during sampling, at least 5 samples inside a large containment.
- The common criterion is 0.01 f/cm³ by PCM with no individual sample above the limit; the licensed project monitor issues written clearance. Any exceedance means reclean and resample the containment.
Recordkeeping
- Exposure monitoring records: 30 years under 29 CFR 1910.1020.
- Medical records: duration of employment plus 30 years.
- WSR: 2 years by generator and disposal site.
- Training and fit-test records, notifications, manometer logs, and bulk sampling reports are kept per DEQ licensing terms and are the first documents an inspector requests.
Worked example
Five clearance samples return 0.006, 0.008, 0.011, 0.007, and 0.009 f/cm³. The mean is under 0.01, but the 0.011 sample fails, so clearance is denied; the crew recleans and resamples rather than averaging away the failure.
Traps
- Sampling after the containment is opened or air machines are off.
- Omitting field blanks.
- Reporting a mean while ignoring the individual maximum.