General Air Sampling in Work Environments

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The following section outlines air sampling techniques and includes a general discussion of collecting air samples. Follow the links here to read descriptions of specific procedures for air sampling using Merck filters, holders, and cassettes.

Air Sample Collection

Airborne particle contamination can vary significantly depending on the operations being carried out. To minimize sample variability, you should sample throughout an entire shift (approximately 8 hours). The final result reflects the average level of exposure. Alternatively, the sampling times can be short, sometimes only a few minutes, to deliberately measure how high the exposure is during specific dust-generating operations.xx

Orifice Flow Rate (L/min.)Minimum Required Vacuum 
mm HgIn HgPSIG
1 300 12 6
2 300 12 6
3 300 12 6
4.9 400 16 8
10 500 20 10
14 550 20 11
Vacuum required for function of flow-limiting orifices.

Air Sampling Procedures

37 mm Monitoring Cassette Method
  1. Thread the flow-limiting orifice (if using one to control flow rate) into the barbed end of the aerosol adapter and attach it to the vacuum hose.
Place flow-limiting orifice into outlet of aerosol adapter.
Place flow-limiting orifice into outlet of aerosol adapter.

  1. Remove bottom (red) plug from three-piece transparent cassette and insert the Luer connector end of the aerosol adapter.
Insert Luer end of aerosol adapter into cassette outlet.
Insert Luer end of aerosol adapter into cassette outlet.

  1. Remove top cover of cassette. Do not remove yellow plug.
     
  2. Apply vacuum for specified time to collect sample.
     
  3. After sampling, replace cassette cover before removing cassette from stand, to protect filter.
     
  4. Send to lab for analysis.
Sample air using 37 mm cassette connected to vacuum pump.
Sample air using 37 mm cassette connected to vacuum pump.


47 mm Stainless Steel Monitor Method
  1. Clean monitor thoroughly to reduce extraneous particles.
     
  2. Perform a microscopic particle count or weigh the filter to determine baseline particle content. (Store filter in PetriSlide™ device until ready for use.)
     
  3. Screw flow-limiting orifice into hose adapter and attach vacuum hose.
     
  4. Place test filter, grid side-up, on support screen in base.
     
  5. Lock filter into place using blue anodized locking ring.
     
  6. Apply vacuum for specified time to collect sample.
     
  7. Open filter holder, remove filter and return to PetriSlide™ device for subsequent evaluation. (Refer to the section on Analysis Techniques)
PetriSlide™ devices
PetriSlide™ devices


Personal Sampling Procedures

Monitoring Cassette Method
  1. Attach hose to cassette adapter (after removing plug and stand).
     
  2. Attach hose to pump. If pump has been recently calibrated, go to step 4.
Aerosol cassette connected to personal sampling pump. Clothing clip fixed to tubing.
Aerosol cassette connected to personal sampling pump. Clothing clip fixed to tubing.

  1. Preferably once a day, calibrate the pump.

    Connect a flow meter to the cassette inlet by removing the red plug in the cassette cover and inserting a connector attached to tubing.

    Alternatively, remove the cassette cover and place the cassette inlet over the flow meter outlet. Adjust the pump flow control screw (for personal sampling, 2 L/min is usually recommended).
Calibrating personal sampling pump using 0-4 L/min flow meter with cassette connected in-line.
Calibrating personal sampling pump using 0-4 L/min flow meter with cassette connected in-line.

  1. Connect the cassette to clothing in the breathing zone.
Cassette attached to worker's clothing in breathing zone. Personal sampling pump clipped to trouser belt.
Cassette attached to worker's clothing in breathing zone. Personal sampling pump clipped to trouser belt.

  1. Note the time and start the pump to collect sample.
     
  2. At the end of the sampling period (commonly 8 hours for personal sampling), replace the inlet cover to protect filter and insert outlet plug. Send to lab for analysis.


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