Installation

• Only have your ventless gas heater installed by a professional. Check to see what state and local certifications are required.
  
  

Safety Grills

• Make sure there is a safety grill installed to prevent pressure from building to dangerous levels. The safety grill should be the appropriate size for the area being heated, and size of the heater, and should meet all local codes.
  
  

Age of Heater

• Make sure that your heater is truly ventless. Before 1999, some models were meant to be used in a room with an open window; however, newer models are required to be safe to use in completely closed rooms.
  
  

Moisture

• Check for built-up moisture. Although newer models don't usually cause enough moisture to develop to case mold, inspect for moisture developing in closed in spaces.
  
  

Inspection

• Have your ventless gas heater inspected annually by the installer to make sure all safety features are performing properly.