Ventless gas heaters are powered by natural gas or propane, also called liquid petroleum or LP. They don't have vents to the outside, like most gas heaters, but they do have meters that monitor the amount of oxygen in the room. If the oxygen drops too low, the heater automatically turns off. Cleaning a ventless gas heater is simple because all you need is a little compressed air and a vacuum.
Shut off the ventless gas heater's power and allow it to cool for 30 minutes or more.
Open the heater's access panel. Spray compressed air into the all of the burner's holes.
Vacuum out the inside of the panel to remove dust and dirt.
Spray compressed air into the hole in the pilot assembly near the burner to remove any dust that might block it.
Dampen a cloth. Wipe the exterior of the ventless gas heater with the cloth to remove dust and dirt.