Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2006

Spontaneous Combustion of Paint Filters

Q. What do you know about spontaneous combustion of dry paint filters?  Managing these used filters? and disposal options?

A. Some paints oxidize after they have been applied, and during the oxidation process they generate heat (the chemical reaction is exothermic.). If the heat cannot dissipate, such as when the paints have been captured by filters that are stacked one on top of the other, the temperature inside the filter pack can increase to a point at which the paint can autoignite. Not all paints oxidize exothermically, but nitrocellulose lacquers are among those that do. To prevent a file, it is suggested that the filters be laid out in individually in a safe place (away from other combustibles) for several days before they are stacked for disposal.  Some companies stack the filters in 55 gallon drums and then soak them in water.

If you are operating a paint spray booth and if you are using a paint that generates heat during oxidation, do not allow too much paint to collect on the filters before changing out the filters. Also, keep the spray booth fan running for several hours after painting has been completed.  The goal is to prevent the temperature within the filter from increasing to the autoignition point.   

Best wishes,

Ron Joseph