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Dissociation of Sulfur Hexafluoride Tracer Gas in the Presence of an Indoor Combustion Source

Dissociation of Sulfur Hexafluoride Tracer Gas in the Presence of an Indoor Combustion Source

Z Guo, R B Mosley, S J Wasson, R C Fortmann, J A McBrian

J Air Waste Manag Assoc. 2001 Apr;51(4):616-22.

PMID: 11321918

Abstract:

As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF6) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H2SO4. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF6 dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF6 concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error. The second type of interference comes from the primary and secondary products of the SF6 dissociation, mainly H2SO4, SO2, HF, and fine particulate matter (PM). In the presence of approximately 5 ppm SF6, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF6 concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF6 concentration is kept at a low ppb level.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AS212869	Sulfur in Odourless Kerosene			Price

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