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Air Sampling Methods:
  • Air sampling is usually conducted before and during abatement, to monitor workers' exposure, and to ensure that the site has been adequately cleaned (post-abatement, or clearance monitoring).
  • Two methods are used to analyze air samples: Phase Contrast Microscopy (PCM) and Transmission Electron Microscopy (TEM):
    • PCM:
      The advantages of PCM are the inexpensive cost, the wide-spread availability, the minimal sample preparation, and quick results. PCM is also the OSHA analytical method. The disadvantages are that it is not asbestos specific and fibers smaller than a given size are not counted.
    • TEM:
      Unlike PCM, TEM is specific for asbestos and even the smallest of fibers are counted. The disadvantages are the expensive costs and slow turnaround times.
  • The clearance level for PCM analysis is 0.01 fibers/cubic centimeter of air (f/cc). Levels above this indicate the need for further cleaning or analysis with TEM to confirm the presence of asbestos fibers opposed to non-asbestos fibers present on the sample. Clearance levels for TEM analysis are less than 70 structures per square millimeter of filter area. The current Occupational Safety & Health Administration, OSHA, Permissible Exposure Limit (PEL-TWA) for asbestos is 0.1 f/cc for an 8-hour day.
  • The National Institute for Occupational Safety and Health, INIOSH, has not established an exposure limit for asbestos, since NIOSH has not identified thresholds for carcinogens that will protect 100% of the population. NIOSH recommends that occupational exposure to carcinogens, including asbestos fibers, be limited to the lowest feasible concentration.
Additional Information:


The Work Order Desk processes all requests for services and issues work orders for maintenance work in “State” buildings. Routine and preventive maintenance in state funded buildings is usually performed at no cost to the department.

To place a work order, either call
243-6091 which is staffed from 8 a.m. to 5 p.m. throughout the work week or submit your request via the Online System.

online work order system

Activity Report

Contact Us

32 Campus Drive
Missoula, Montana 59812
Office: (406) 243-2788
Work Order desk: (406) 243-6091
FAX: (406) 243-6612