Controlled bench-scale laboratory experiments were conducted to evaluate the recovery of ammonia (NH 3 ) and hydrogen sulfide (H 2 S) from dynamic isolation flux chambers. H 2 S (80 -4000 ppb) and NH 3 (5000 -40,000 ppb) samples were diffused through the flux chamber to simulate ground level area source emissions while measuring the inlet and outlet flux chamber concentrations simultaneously. Results showed that the recovery of H 2 S during a 30-min sampling time was almost complete for concentrations Ͼ2000 ppb. At the lowest concentration of 80 ppb, 92.55% of the H 2 S could be recovered during the given sampling period. NH 3 emissions exhibited similar behavior between concentrations of 5000 -40,000 ppb.Within the 30-min sampling period, 92.62% of the 5000-ppb NH 3 sample could be recovered. Complete recovery was achieved for concentrations Ͼ40,000 ppb. Predictive equations were developed for gas adsorption. From these equations, the maximum difference between chamber inlet and outlet concentrations of NH 3 or H 2 S was predicted to be 7.5% at the lowest concentration used for either gas.In the calculation of emission factors for NH 3 and H 2 S, no adsorption correction factor is recommended for concentrations Ͼ37,500 ppb and 2100 ppb for NH 3 and H 2 S, respectively. The reported differences in outlet and inlet concentration above these ranges are outside the fullscale sensitivity of the gas sensing equipment. The use of 46 -90 m of Teflon tubing with the flux chambers has apparently no effect on gas adsorption, because recovery was completed almost instantaneously at the beginning of the tests.
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