Vent free blue flame heater uses natural gas or liquid propane. No conversion kit required. Unit is completely vent free with no outside duct or chimney needed. Unit is 99% efficient and has an ODS (oxygen depletion sensor) for safety. Blue flame heaters are designed to heat the air in the room first, circulating the warmth throughout a room like a central heating system. No electricity is required - perfect for use during power outages. Push button piezo ignition offers easy start up.