The scope of this method is to identify asbestos in settled dust and provide asbestos structures per unit area of sampled surface. This allows for potentially contaminated areas to be evaluated without resuspending and further contaminating the area in question. The following is a general outline of how microvacuum samples are collected. To order a copy of Method #5755-03, from ASTM, simply click here.

The basic procedure is outlined as follows:

1. The inlet orifice of commercially available 25mm or 37mm (MCE or PC) microvacuum cassette is fitted with a one inch plastic tube (nozzle) cut at a 45 degree angle.
   
   

   Typical Microvacuum Cassette

   
   
2. The cassette is attached to a low volume sampling pump by an appropriate length of plastic tubing and calibrated at (2L/min).
3. The sampling area of interest is determined and measured. Usually 100 square centimeters is sampled (approximately 4 inches by 4 inches). Larger areas can be vacuumed on cleaner surfaces.
4. The area is vacuumed for at least two minutes by moving the cassette at least two diagonal passes until no visible dust or particulate remain. Care must be taken to allow a vacuum break at the nozzle to avoid pushing the dust around rather than allowing it to enter the cassette.
5. The cassette is then held nozzle up, the pump is turned off, and the nozzle is placed inside the cassette. Place the plugs back into the cassette, wet wipe and tape up for shipment using fiber free packing to the analytical laboratory.
6. Include clearly labeled cassettes, completed information sheets, and a blank cassette with nozzle for a field blank.

Concentrations that have been established in the analytical community for levels in microvacuum samples are as follows:

Less than 1000 Str/cm2 (929,000 Str/ft2) considered low Greater than 10,000 Str/cm2 (9,290,000 Str/ft2) is considered above background Greater than 100,000 Str/cm2 (92,900,000 Str/ft2) is considered high

(Millette & Mount EIA Meeting 1995; Ewing & Alber, Observations of settled Asbestos Dust in Buildings, EIA Technical Journal, Summer 1996)