The U.S. Department of Energy ("DOE") is amending the test procedure for direct heating equipment to incorporate by reference the most recent versions of the industry consensus test standards previously referenced in the Federal test procedure, while maintaining the existing oil pressure measurement error value. DOE is also updating definitions regarding unvented heaters, accounting for multiple operational modes, specifying the input rate for conducting the cyclic condensate collection test, specifying the use of manufacturer values for gas supply pressure in certain circumstances, specifying the allowable range of regulator outlet pressure and specific gravity, providing an option to use fewer thermocouples in the thermocouple grid for models with small-diameter flues, clarifying instructions for calculations regarding condensate mass measurements, and specifying the methods to appropriately shield thermocouples from radiation.