A complete solution to explosion protection in facilities processing combustible dusts or flammable gases often involves consideration of dust and gas conveying systems as well as primary process volumes. The pipes or ducts of the conveying system can serve as efficient means of propagating deflagrations from point to point in a plant. Subsequent to the implementation of the requirements of the Clean Air Act Amendments of 1990 the need for explosion protection systems on pipes and ducts has increased. VOCs and vapors of hazardous chemicals are commonly incinerated. Such systems are subject to flash back failure and ignition of flammable gases in the feed pipe. Feed bins and product collectors up and down stream are at risk of ignition from sparks generated at grinding stations. Systems feeding dusty solids to furnaces are subject to flash back. This paper summarizes present day methods of detecting pipeline deflagration events and intercepting same using either fast closing valves or chemical barrier systems. Modes of deflagration detection, type and placement of barriers are discussed. The impact of the phase out of the production of halons in this area is also discussed. Examples of combustible dust and flammable gas protection systems are described.