While the features of vent wall heaters vary by manufacturer and unit, Williams offers direct vent heaters that have a sealed combustion chamber and piezo-electric pilot light and continue to operate during power failures. The sealed chamber and direct vent setup vents exhaust gases directly to the outside and provides a constant supply of oxygen for combustion to protect the quality of indoor air.
When the wall heater is combined with a blower, it provides even heat throughout the room; however, the blower requires electrical power to operate. Many of the units operate using a thermostat that controls the temperature automatically by cycling the heat to maintain it within the range the user sets. The units are a good choice for home additions that do not burden the existing heating system, but larger units provide an option for heating an entire home.
Direct vent systems are available for use with propane or natural gas as a fuel source. Some manufacturers offer kits that allow converting the fuel type for the wall heaters while others require the user purchase a unit for the specific fuel type. Most systems vent directly through the outside wall behind the unit, but others use a vent that exits through the ceiling and roof.