A company had a spray painting operation to paint automotive parts. The spray painting was done in a paint booth to reduce worker's exposure and to collect any paint droplet that might be entrained in the exhaust air. The paint droplets were collected by fibrous filters. At the end of each day, the filters were removed, placed in plastic bags and stored for disposal in a separate building Due to environmental concerns over volatile emissions from paint solvents, the paint supplier reformulated the paint to use a less volatile solvent. This change was done in consultation with the paint company. Several tests were done to ensure that the reformulated paint worked well with the existing spray equipment and that the resulting quality was satisfactory. The company eventually switched over to the reformulated paint. Several days later this disposal building caught on fire, apparently due to a fire started by the paint filters. Can you explain how this happened? Do you have any suggestions for prevention?