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 Technology & Development Center |
Real-Time
Smoke
Particulate Sampling
Fire Storm 2000
During the summer of 2000, extremely dry, hot conditions resulted in large natural wildfires throughout western Montana and Idaho. Area residents called the fire season Fire Storm 2000. Massive amounts of smoke settled in the valleys around western Montana and Idaho. The U.S. Department of Agriculture, Forest Service, Missoula Technology and Development Center (MTDC) deployed and evaluated real-time, particulate monitoring instruments to measure the smoke particulate concentrations. The center maintained two sets of real-time instruments, one in Missoula, MT, and one in Hamilton, MT. A U.S. Environmental Protection Agency (EPA) Federal Reference Method (FRM) PM2.5 sampler was collocated with the instruments at each location. The main goal of the instrument collocation study during Fire Storm 2000 was to determine the accuracy of the real-time instruments when measuring smoke particulate concentrations from natural wildfires.
Airborne particulates, especially particles smaller than 2.5 microns (µm) in diameter (PM2.5), pose potential health, visibility, safety, and nuisance problems at certain concentrations. Smoke particles, whether from prescribed burning or natural wildfire, are generally smaller than 2.5 µm and pose a potential health threat to individuals, especially persons with respiratory problems. Small particles are also the main reason smoke reduces visibility. The EPA has proposed annual and 24-h average PM2.5 standards to protect human health. Regional haze regulations to improve visibility also target fine particles.
The center has been evaluating commercially available optical instruments that estimate particulate concentration in real time. These instruments can provide land managers and air quality specialists with valuable real-time airborne particulate concentration information during managed forest and rangeland burning. Managing smoke to protect human health and public welfare is an essential part of each prescribed burn plan. The proper use of ambient air quality monitoring can help ensure that prescribed burning complies with State and Federal air-quality laws and regulations while satisfying land management objectives.
The real-time particulate monitoring instruments can also provide local and State health department personnel, wildfire safety personnel, and communities with important particulate concentration information during times of severe wildland fires. Many rural communities do not have instruments to assess particulate concentrations. Communities can rely on visual techniques to estimate particulate concentrations, but these techniques are subjective and less accurate. Real-time instruments could provide community officials with more timely information to issue air quality stage alerts designed to protect local area residents.
The center has published two reports (figure 1), Laboratory Evaluation of Two Optical Instruments for Real-Time Particulate Monitoring of Smoke (9925-2806-MTDC) and Evaluation of Optical Instruments for Real-Time Continuous Monitoring of Smoke Particulates (0025-2860-MTDC). These reports provide details on real-time instrument evaluations in laboratory and field situations. Filter-based, direct mass measurements, specified by the EPA as reference or equivalent methods, are the standard techniques for determining particulate mass concentrations. Results from gravimetric samplers were used as the assumed actual representative particulate concentration in all the tests. While most of the results in the two reports were from laboratory work, the instruments were also collocated downwind of several prescribed burns to test them in field situations. We found it difficult to obtain results from prescribed burning activities. Most of the prescribed burns were small and did not produce large amounts of smoke. More importantly, these burns were conducted during conditions that allowed the smoke to disperse. Regulatory requirements dictate that airsheds must be in suitable conditions before burning to prevent smoke from impacting populated areas. Most of the smoke from the prescribed burns lofted high into the air, far above our instruments. The numerous, intense fires during Fire Storm 2000 provided us with an excellent chance to evaluate the real-time instruments during natural wildfire conditions.
Figure 1—Two reports (9925-2806-MTDC
and
0025-2860-MTDC)
detail the evaluation of several
real-time particulate monitors in a laboratory and field setting.
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