Substance-induced anxiety disorder Diesel particulate filter, filters the particulate matter by forcing the exhaust gases to pass through a ceramic wall flow filter. The ceramic wall flow filter features a porous wall and is single ended. When the spent gases are forcibly passed through the porous wall, the particulate matter is filtered along with the gas is discrete thereby lowering the particulate emission inside atmosphere. Today's building codes state spaces using furnaces will need to have means for getting together again combustion air as it used. Newer homes have ducting installed, during construction, thats liable to bring oxygen on the surface to a area close to the furnace. This ducting, usually called constitute air duct, or combustion make-up air, is sized according to the capacity in the furnace.