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CH3041
PERSONAL AIR
SAMPLING II
• Air samples must be taken over a
duration
to give TWA (Time Weighted Averages).
to give TWA (Time Weighted Averages).
• The OES (Occupational Exposure Standard ) is found in the MSDS on the basis of TWA.
• The normal interval is 8 hrs for a
pollutant.
eg. NH3 8 h OES 25 ppmv.
• If a gas
concentration fluctuates rapidly then
shorter periods may be necessary
eg. NH3 10 min OES 35 ppmv.
eg. NH3 10 min OES 35 ppmv.
