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Evaluation of Optical Instruments for Real-Time Continuous Monitoring of Smoke Particulates
Objectives—The 2000 laboratory tests had several objectives. One objective was to conduct tests similar to the 1998 laboratory tests on several new instruments to compare their performance to the other instruments. The new instruments included the Met One GT-640, the Optec NGN-3 nephelometer, and the Andersen aethalometer. Another objective was to obtain samples at lower concentrations of particulate (under 150 µg/m³) than were measured during the previous laboratory tests. We also conducted several tests at high relative humidities (above 70 percent) to determine the effectiveness of the inlet heaters. Finally, we compared gravimetric samplers.
Location—The 2000 laboratory tests were conducted at the Fire Sciences Laboratory's smoke chamber. The instruments were placed side by side on a platform 55 ft above the chamber floor.
Instruments—The instruments included in the 2000 laboratory tests were:
A total of 11 instruments and seven different makes or models were tested. All instruments were configured with their respective PM2.5 cutoff inlet and inlet heater. To maintain consistency with the previous laboratory and field tests, the Radiance Research nephelometer was configured to estimate total suspended particulate.
Test Descriptions—Except for the high-humidity tests, all the experiments were conducted at ambient conditions inside the closed chamber. Again, very small beds of dry ponderosa-pine needles (weighing from 50 to 150 g) were burned to generate the smoke. These beds were much smaller than in the 1998 tests where we burned more needles to generate higher particulate levels.
A number of tests were conducted to evaluate the performance of identical instruments, specifically the MIE Data-Ram, the Radiance Research nephelometers, the Met One GT-640's, and the FRM samplers. We not only determined the accuracy of each real-time instrument compared to the gravimetric instrument, but we also compared each of the instruments to another like it.
High-humidity tests were performed between similar instruments with and without their respective inlet heaters.
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