Abstract: The invention relates to the application of powder coatings to vital components of equipment in various industries. The apparatus comprises a barrel for application of powder to the article and a gas distribution unit which connects fuel gas feeding passages and a purging gas feeding passage to the barrel. Gases are fed to outlet pipes of gas passages from appropriate gas sources under pressure through valves mounted in the pipes. The outlet opening of the purging gas passage may, in some embodiments, be located upstream of the zone of admission of fuel gases to the barrel in the path of flow of purging gas. The pressure of the purging gas source exceeds the pressure of each of the fuel gas sources so that, upon feeding fuel gas to the barrel, the valves mounted at the outlet pipes of the fuel gas passages shut-off these pipes. After the valve mounted in the purging gas passage is closed, the valves mounted in the fuel pipes admit fuel gases to the barrel to build-up a detonation wave.