In a deposition system, such as a TiN deposition system where TiCl.sub.4 and NH.sub.3 are reacted in a process chamber to produce TiN thin film coatings, a second reactor is included between the process chamber and the vacuum pump to react enough of the theretofore unreacted feed gases to consume substantially all of at least one of them so that further reactions that could otherwise produce solids, which cause excessive vacuum pump wear, are presented. The second reactor is preferably positioned between a cooled condensation trap downstream from the process chamber and vacuum pump, and it is also applicable in atomic layer deposition (ALD) systems for TiN, WN, and other materials as well as in chemical vapor deposition (CVD) systems for those and other materials.