This recommended practice should be considered in the installation@ maintenance and testing of firebox flame arrestors installed on the air intake of oilfield production equipment. Flame arrestors are commonly used on indirect heaters@ emulsion treaters@ glycol reconcentrators and other equipment used to heat fluids in production operations. These flame arrestors are designed to prevent flashback through the arrestor in the event that combustible fluids in the atmosphere should be drawn into the heater through the air intake and come in contact with the main burner or pilot flames. This recommended practice is limited to gas fired@ natural draft burner systems with continuously burning pilots. Flame arrestors for oil fired burners or burner systems using forced draft or induced draft are outside the coverage of this recommended practice. Also excluded from coverage of this recommended practice are burner systems in which a spark produced by the system could cause an internal explosion such as with a spark ignition device. Equipment known as line arrestors@ tank arrestors@ spark arrestors@ or stack arrestors are outside the coverage of this recommended practice. Some of the recommended practices for field testing after installation may not be applicable to equipment located in confined areas. The user may modify these recommended practices as required to satisfy his own specific needs.