LP Air Mixing Orifice 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 the bottom of the burner ring and/or burner pan. Draws in air to promote a cleaner burn. 1/2″ connection. Available in 4 different BTU’s to match your burner requirements and type of LP tank used. 75,000, 90,000, 150,000 and 300,000 BTU’s  You will need to provide proper venting in the base of your gas fire pit to allow the orifice to draw in air, and for safety when using LP Liquid Propane gas.