LP Propane Air Mixing Orifice This LP Orifice is for the big BTU burners. Available in 300k or 400k BTU’s.  Since propane gas requires more oxygen than natural gas, air mixers must be used to obtain proper propane combustion.  This ensures that air entering through the vent’s opening fuses and dilutes with the propane–allowing for more efficient burning flames. Not only is it an essential tool for your propane burner, but it also has the additional benefit of reducing soot production created by using pure propane. Made of durable brass with stainless steel coupler and nipple to fit your needs.  Use this orifice when using LP (Liquid Propane Gas) to reduce the sooting and carbon deposits. Attach in-line to bottom of burner ring. Available in either 300,000 or 400,00 BTU’s with 3/4″ threads and a stainless steel coupler and nipple to fit your hook-up needs.