A pollution control device suitable for use with an internal combustion engine (e.g., a diesel engine) and comprising a pollution control element arranged in a casing with non-woven mat disposed between the casing and the pollution control element, said non-woven mat being a non-intumescent mat comprising at least 90% by weight based on the total weight of the mat of chopped magnesium aluminum silicate glass fibers that have a number average diameter of 5.mu. or more and a length of 0.5 to 15 cm, said glass fibers being needle punched or stitch bonded and said mat being free or substantially free of organic binder.