Ambient Air quality Monitoring Guidlines. - Maharashtra Pollution ...

9.4.7 A randomly selected 5-10% of the samples should be reanalyzed as apart of an
internal quality assurance program.
9.5 Sampling Efficiency
The overall average efficiency is 82% from 40 to 750 µg NO - 2/m 3 (0.02 to 0.4
ppm) 3 .
10.0 CALCULATIONS
10.1 Air Volume - Calculate the volume of air samples as follows :
Where :
F1 + Ff
V = ----------- x ts x 10 -6
2
V = Volume of air sample, m 3
F1 = Air flow rate before sampling, cm 3 /min
Ff = Air flow rate after sampling, cm 3 /min
ts = Sampling time, min
10 -6 = Conversion of cm 3 to m 3
If, the temperature and pressure conditions at the time of the initial and final air
flow rate measurements are substantially different from the conditions under
which the flowmeter was calibrated, appropriate corrections to the flow rate
measurements may be made to improve the accuracy of the resultant NO2
concentration measurement. The mathematical form of these corrections
depends on the type of flowmeter used; consult an appropriate reference for
guidance.
10.2 NO - 2 Concentration in Analyzed Sample - Determine µg NO - 2/ml graphically
from the calibration curve or compute from the slope and intercept values (see
9.3.3).
10.4 NO2 Concentration in Air Sample - Calculate as µg of NO2 per cubic meter of
air as follows :
µg/NO - 2 x Vs
µg NO2/m 3 = ------------------ x D
Va x 0.82 x Vt
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