Is Vent-Free Gas Heating Right For Me?
 
 

While most states permit installation of vent-free gas heating appliances, a handful of states still prohibit residential use. Very often, that's because a state's building codes haven't caught up with vent-free gas technology.

Currently seven states prohibit residential use: Alaska, Massachusetts*, Montana, Minnesota*, Colorado*, Utah*, and California*. However, many local and state codes are currently being revised to reflect acceptance of this new technology.

Click for map of states and their codes.

*Several counties and municipalities in Massachusetts, California, Colorado, Minnesota and Utah permit the product. Wisconsin restricts installation in homes built after 1980

Because states, counties and municipalities adopt various codes, please check with your installer or local code officials to assure the current code in the city where you plan to install permits vent-free gas appliances.
 
 
Other Considerations:
  • Homes of Extremely Tight Construction
    If you home shows symptoms of inadequately ventilated home (moisture on inside of windows, mildew, and shower or bath humidity lingers), additional ventilation may be required prior to adding additional  vent-free gas appliances.
  • Homes with Other Fuel Burning Appliances
         If there are other fuel burning appliances that use inside air for combustion (i.e. gas ranges, fireplaces, clothes dryers) in the area you plan to operate your vent-free heating product, you must provide adequate fresh air to support the operation of all the appliances. Consult your installer and refer to the Air for Combustion and Ventilation section of the Owners and Installation Manual for your specific vent-free appliance.
  • Homes at High Altitude
    (i.e. homes at 4,500 feet above sea level or higher) - may experience nuisance pilot outage and flame shutdown due to lower atmospheric pressure.
  • Bedrooms and Bathrooms
    In many areas the installation of vent-free products is permitted up to 10,000 Btu in bedrooms and 6,000 Btu in bathrooms - ANSI Z21.112 Standard and National Fuel Gas Code permit wall mounted installations of vent-free gas heater of 10,000 Btu or less in bedrooms and 6,000 Btu or less in bathrooms.
  • Water Vapor Levels
    When outside temperatures fall, so does relative humidity (water vapor). Many people in cold climates use humidifiers to supplement indoor moisture. Vent-Free gas heating products are not intended to replace humidifiers, but they do perform a similar function. AGAR researchers examined relative humidity at 0 degree F outdoor temperature and a 0.25 air change rate ( American Society od Heating Refrigerating and Air Conditioning Engineer's minimum acceptable air change rate is .035/hour). Even under these extreme conditions, the highest relative humidity measured was 49 percent. That's still well below the recognized comfort level of 60 percent.
 

"Let's Clear the Air" Regarding the Effect of Vent-Free Gas Heaters on Indoor Air  Quality
   
    In 1995, the scientist at the American Gas Association's Research Division (AGAR) tested the levels of all five major contributors of indoor air quality - oxygen, carbon monoxide, carbon dioxide, nitrogen dioxide and water vapor (humidity) - against the latest Indoor Air Quality (IAQ) guidelines and concluded that vent-free gas heating products performed well within nationally recognized guidelines for indoor air quality.
    This research proves that vent-free gas heating products meets applicable emissions requirements, even when used over extended time periods, among sensitive populations, and even with oversized units.
 
 

AGA RESEARCH COMPARISON OF RELATED IAQ GUIDELINES TO VENT-FREE GAS PRODUCTS' EMISSIONS2
 
Combustion by product Specifying agency National IAQ Standard/Guidelines
exposure level/time		 Vent-free gas product
Carbon Monoxide (CO) CPSC 15 pp, avg/8 hours
25 ppm avg/1 hour		 2.5 ppm/8 hours
1.5 ppm/1 hour
Nitrogen Dioxide (NO2) CPSC 0.3 ppm avg/1 hour 0.22 pm/1 hour
Carbon Dioxide (CO2) OSHA 5000 ppm avg/8 hours 1500 ppm/8 hours
Oxygen (O2) NIOSH 19.5% minimum/continuous 20.4% continuous
Humidity (H2O) ASHRAE 60% maximum/continuous 36.5% maximum
with no condensation
 
 
NATIONAL BUILDING/MODEL CODES
The following six model building codes permit the installation of listed vent-free products:
  • National Fire Protection Association (NFPA)
  • Building Officials and Code Administrators (BOCA)
  • Southern Building Code Congress International (SBCCI)
  • Council of American Building Officials (CABO)
  • International Mechanical Code (IMC)
  • International Fuel Gas Code

Only the International Conference of Building Officials-Uniform Mechanical Code (ICBO-UMC) does not permit the product