Smoke Particulate Monitors: 2006 Update, Page 4

Smoke Particulate Monitors: 2006 Update

Goals and Methods

The main goal of this evaluation was to determine the accuracy of the real-time instruments when estimating smoke particulate concentrations. This was accomplished by comparing the real-time results to results from an FRM gravimetric sampler. A correction algorithm can then be established for each type of instrument that allows for better estimation of smoke particulate concentrations in the field. We were also interested in any difference in the results from the E-BAM with the ac pump compared to the dc pump. We tested at least two instruments of each model so we could begin to understand the consistency in performance between identical instruments.

All the instruments except the DUSTTRAK were configured with their respective PM_2.5 particle size cutoff device installed. We used the PM₁₀ cutoff inlet with the DUSTTRAK because Forest Service personnel who use the instrument for smoke monitoring requested that we test the monitor in this configuration. We conducted one test with a DUSTTRAK configured with the PM_2.5 cutoff inlet to determine its effectiveness. We calibrated all the instruments before the tests. Instrument sample airflows were checked. All the real-time instruments were set for an average time of 1 minute and were run continuously throughout the tests.

Before testing each day, a self test was conducted on the E-BAM monitors to ensure that they were functioning properly. The E-Sampler, DUSTTRAK, and DataRAM monitors were calibrated and zeroed using procedures recommended by the manufacturer. The DataRAM 4s were programmed with the particle size correction feature set to "enable," which allows the monitor to correct the estimated mass concentration based on the mean particle diameter.

The FRM sampler was programmed to run for different lengths of time, depending on the smoke particulate concentrations. For these tests, the FRM was programmed to run between 20 and 120 minutes. After the filters were weighed, the mass of the collected particulate was divided by the total volume of air drawn through the filter for the particular time period to obtain the average mass concentration. That value was compared to the average mass concentration estimated by the real-time instruments during the same period.