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Real-Time
Smoke
Particulate Sampling
Fire Storm 2000
Gravimetric-based instruments were used in the evaluation to produce standard results for comparison with the real-time samplers. Gravimetric- or filter-based instruments work by drawing air at a controlled rate through a filter that collects the fine particulate matter. The filter is carefully weighed at a special facility before and after sampling. This method provides very accurate results of the quantity of particulate that was collected during the test period. The particulate mass value is divided by the total volume of air drawn through the filter, yielding the average mass concentration for the test period, typically in micrograms per cubic meter.
The BGI, Inc., PQ 200 (figure 15) sampler was used in the real-time collocation study. One sampler was located at Missoula and another in Hamilton, MT. They both have similar design, performance characteristics, and operational requirements. The BGI PQ 200 is a microprocessor-controlled, volumetric flow rate air-sampling instrument that obtains a valid PM2.5 air sample. Two inertial separators designed by the EPA separate particulate matter finer than 2.5 µm. These particulates are collected on a 47-mm Teflon membrane at a volumetric sample rate of 16.67 L/min.
Figure 15—The BGI PQ 200 federal reference
method PM2.5 air sampler.
Measurements are made at ambient temperature and pressure. A microprocessor and volumetric flow control system are integrated to maintain constant flow. Volume flow rate, 5-min average ambient temperature and pressure, and filter temperature and pressure are continuously logged into the processor memory. The operator recovers measured values and flags (indicating anomalies) by downloading the summary to a laptop computer. The instruments may be powered by an internal battery, external batteries, or solar power.
Filters collected by the BGI PQ 200s were weighed at the Montana Department of Public Health and Human Services environmental laboratory in Helena, MT.
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