Environmental Sampling Techniques - Fundamentals of Environmental Sampling and Analysis - page 93

perpendicular to the gas flow is divided into specified number of equal area. The
required number and location of traverse points can then be determined for gas
velocity measurement and sample extraction.
Practical tips
Note the difference in sampling regulations and methodologies of various
agencies (mainly EPA and OSHA) for various projects dealing with ambient
air, workplace air, or emission from a smoke stack (ACGIH, 1989).
Like testing of other media, ''informal'' testing differs from ''compliance''
testing. Use a common sense approach with sample equipment for the
former. For the regulatory compliance testing, which are mostly conducted
by certified professional testing labs, it requires expensive equipment and
complex methodologies.
The choice of sample locations is extremely important for the accuracy of air
sampling. The key is to find a place that is either representative of the local
air quality, or depending on your objectives, represent a worst case. When
ambient air is collected, it is most useful to pick a location that most closely
approximates actual human exposure.
It is relevant to emphasize the importance of a good air-flow measurement.
When mass emission rate of a compound (lb/hr, for example) is reported, the
final calculation involves multiplying a pollutant concentration by the air-
flow. The best concentration measurement in the work can be horribly
skewed by an incorrect air flow determination (Bodger, 2003).
Document sampling conditions at the collection time and site, including
meteorological (wind direction, wind speed, temperature, atmospheric sta-
bility, atmospheric pressure, humidity, and precipitation), and topographical
(building, mountains, hills, valleys, lakes, and sea) data. These factors will
help later data interpretations.
REFERENCES
American Conference of Governmental Industrial Hygienist (ACGIH) (2001), Air Sampling Instruments,
9th Edition, Cincinnati, OH.
American Public Health Association, American Water Works Association, Water Environment Federation
(1998), Standard Methods for the Examination of Water and Wastewater, 20th edition. Edited by:
Clesceri, L.S., Greenberg, A.E., Eaton, A.D., Published By: American Public Health Association.
*B ODGER K (2003), Fundamentals of Environmental Sampling, Government Institutes, Rockville, MD.
C HRISTIAN GD (2004), Analytical Chemistry, 6th Edition, John Wiley & Sons Hoboken, NJ.
Cowgillum (1988), SamplingWaters: The Impact of sample variability on planning and confidence Levels,
In Keith LH (1988), principles of Environmental sampling, American chemical society, Washing, DC.
Forestry Suppliers, Inc., http://www.forestry-suppliers.com; Ecotech Pty Ltd, http://www.ecotech.com.au/
(For pictures of common sampling tools).
Hazardous Materials Training and Research Institute (HMTRI) (2002), Site Characterization Sampling
and Analysis, John Wiley & Sons Hoboken, NJ.
* Suggested Readings