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Evaluation of Optical Instruments for Real-Time Continuous Monitoring of Smoke Particulates

Evaluation Results and Discussion (continued)

Real-Time Continuous Monitoring Results (continued)

Radiance Research Nephelometer (continued)

2000 Laboratory Tests (continued)—At high humidities (higher than 70 percent), the Radiance nephelometers overestimated the mass concentrations by 51 percent (with inlet heater) and 64 percent (without inlet heater, figures 32 and 33). The Radiance nephelometer with the inlet heater had a slope of 1.51 and an R² value of 0.87. The nephelometer without the inlet heater had a slope of 1.65 and an R²: value of 0.84. The Radiance nephelometer with the inlet heater read 9 percent lower than the nephelometer without the heater (slope = 0.91, R² = 0.98, N = 14).

Graph: Comparison of Radiance Research nephelometers with and without inlet heaters at high humidities, more than 70 percent. Gravimetric concentration versus Radiance concentration.

Figure 32—Comparison of the results from the Radiance
Research nephelometers and the gravimetric sampler.
Radiance No. 1 had an inlet heater while Radiance No. 2
did not. Gravimetric results are from the Federal Reference
Method sampler.

Graph: Comparison of two Radiance Research nephelometers with and without inlet heaters at high humiditeis, more than 70 percent. Radiance without inlet heater versus Radiance with inlet heater.

Figure 33—Comparison of the two Radiance Research
nephelometers used during the high-humidity tests.

Discussion—The Radiance Research nephelometer performed much like the DataRam. It overestimated mass concentrations by 80 to 90 percent during the 1998 laboratory tests. The overestimate was 10 percent during the 2000 laboratory tests. The field test overestimates were between the 1998 and 2000 laboratory overestimates. The difference in the laboratory results may be attributable to differences in the amount of needles burned during the tests.

The Radiance nephelometers showed excellent consistency when compared against each other. The instruments consistently read within 5 percent of each other with very high correlations.

The high-humidity tests indicated that the inlet heater does affect the mass concentration estimations. The nephelometer with the inlet heater had readings 9 percent lower than the one without.

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