The purpose of the study was to characterize the effects of selected parameters on the evaluation of wildfire smoke residues when evaluating their impact on structures, primarily residential properties but other structures as well. The study included wildfire smoke residue samples that were collected from houses that were potentially impacted by various wildfires in northern California. The parameters included the frequency with which a residue was detected, the distance of the site from the wildfire, the elapsed time between the inspection and the wildfire, the effect of sampling location in the structure, the effects of sampling method, and the numerical guideline for evaluating if a structure had been impacted by wildfire smoke residues.

Rationale for Sampling Method

In practice, wet wipes may perform better than tape lifts for sampling hard surfaces. In addition, wet wipes may be the preferred residue sampling method within the industry. About 80% of the wildfire smoke residue samples submitted to the EMSL facility in Cinnaminson, NJ were wipes, 10% were tape lifts, and 10% were micro-vacuum samples. At EMSL’s Pasadena, CA facility, 70% of the samples were wipes, 25% were tape lifts, and 5% were micro-vacuums.

The wet-wipe sampling method offered several potential advantages for collecting wildfire smoke residues, especially since char was expected to be the dominant wildfire smoke residue.

First, the method could be applied to both smooth and intricate hard surfaces, as well as heavily loaded surfaces. Second, the sample preparation step increased homogeneity of subsamples for analysis by optical microscopy, which reduced analytical.

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