Filters in the discard bin from a paint booth caught fire. MVA Scientific Consultants was asked to characterize the fire debris.
Examination of the debris by polarized light microscopy (PLM) revealed agglomerations of spherical particles and amorphous, porous black material with a “sooty” appearance. Fiberglass consistent with fragments of air filters was also observed (Figure 1).
Red, white and blue agglomerates and black agglomerates (Figure 2) were analyzed by scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) and Fourier transform infrared microspectrophotometry (FTIR).
Analyses of the multi-colored spheres (Figure 3) showed they were consistent with spray paint with evidence of talc and other silicate paint fillers. The black aggregates (Figure 4) appeared to be relics of burned paint spheres with magnesium and silicon x-ray peaks in proportions indicative of talc.
Volatile organic components were found in the air in the sample container by gas chromatography. Five of the organic components were rated 3 for flammability, with flash points below 100°F.
Microscopy confirmed that the filters themselves were non-flammable and were not involved with the fire. There was no evidence that might suggest cigarette butts, matches, wood or cloth products were involved in the combustion.
Because some organic chemicals were detected that had low flash points, the company eliminated the possibility of spontaneous combustion by increasing the ventilation around the discard bin.