LETS CLEAR THE AIR

It's time to clear away the fog of misinformation regarding the impact of VENT-FREE gas product emissions on indoor air quality (IAQ).

The American Gas Association Research Division (AGAR),  working on a grant from the Gas Appliance Manufacturers Association (GAMA), recently conducted conclusive new independent research which shows vent-free gas products perform well within the current accepted national IAQ standards and recomendations. 
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AGA RESEARCH COMPARISON
OF NATIONAL IAQ STANDARDS TO VENT-FREE GAS PRODUCTS EMISSIONS
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Combustion                     Specifying       National IAQ Standard        Vent-free
by-product                       Agency            Exposure level/time            Gas product

Carbon Monoxide (CO)      CPSC            15 ppm avg/8 hrs.                   2.5 ppm/8 hrs.
                                                                25 ppm avg/1 hour                 1.5 ppm/1 hour

Nitrogen Dioxide (NO2)      CPSC            0.3 ppm avg/1 hour                0.22 ppm/1 hour

Carbon Dioxide (CO2)        OSHA           5000 ppm avg/8 hrs.               1500 ppm/8 hrs.

Oxygen (O2)                      NIOSH          19.5% Min./continuous             20.4% continuous 

Humidity (H20)                   ASHRAE       60% Max./continuous              36.5 maximum
                                                                                                         w/ no condensation
                                                                                                        
                                                                                                                                                   
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The findings summarized above consider a broad range of operating conditions for btu input, volume and air exchange rates, including oversized units. 

Bottom line-----------Since the early 1980s, more than 4 million vent-free gas heaters and fireplace products have been installed in U.S. homes.  Now the new AGAR data has verified that listed vent-free gas products more than satisfy IAQ standards, when used over long periods and among sensitive populations. 

If you would like a complete copy of the AGAR study, just write:  Vent-Free Gas Products Division, GAMA, P.O. Box 9245, Arlington VA. 22219 or fax:  703-525-0718

What the Numbers Mean

The table above compares measured emissions from listed vent-free gas products with national indoor air quality guidelines. Here is what each by-product is and why it matters:

  • Carbon monoxide (CO) is an odorless gas produced by incomplete combustion. A properly adjusted vent-free burner with logs placed correctly produces very little CO.
  • Nitrogen dioxide (NO2) can irritate the lungs at high levels. The study measured levels below the CPSC guideline.
  • Carbon dioxide (CO2) is a normal product of burning gas, just as it is a product of breathing.
  • Oxygen (O2) stayed above the NIOSH minimum. Every vent-free appliance also has an oxygen depletion sensor (ODS) that shuts off the gas if oxygen drops too low.
  • Water vapor is released when gas burns. The study found humidity stayed below the ASHRAE maximum, and in dry winter air many homeowners find the added moisture comfortable.

How to Keep Vent-Free Heat Safe and Clean

  • Size it correctly. The National Fuel Gas Code limits vent-free appliances to 40,000 BTU per hour, 10,000 in bedrooms and 6,000 in bathrooms, and to 20 BTU per hour per cubic foot of room volume.
  • Install it right. Have a qualified gas technician install the unit and follow the manufacturer’s instructions and your local codes.
  • Keep the logs in place. Logs that are moved or broken can affect the flame and increase soot and CO. Replace damaged logs only with the manufacturer’s parts.
  • Clean and inspect yearly. An annual check by a service technician keeps the burner, pilot and ODS working properly.
  • Use carbon monoxide alarms. CO alarms are a smart safety measure in every home with fuel-burning appliances.
  • Follow the operating instructions. The owner’s manual explains run times and ventilation. Vent-free products are designed for supplemental heat.

Standards and Further Reading

Vent-free gas heating products sold in the U.S. are certified to the ANSI Z21.11.2 standard for unvented room heaters. The Gas Appliance Manufacturers Association (GAMA) mentioned above merged with the Air-Conditioning and Refrigeration Institute in 2008 to form AHRI, so the mailing address for the study may no longer be current. For up-to-date consumer information, visit the Vent-Free Gas Products Alliance at ventfree.org.

Ready to compare products? See our vent-free gas logs, vent-free fireplaces and vent-free fireplace inserts, or the full fireplace index.

Frequently Asked Questions

Are vent-free gas logs safe to use indoors?

Listed vent-free gas logs that are correctly sized, installed and maintained are designed to meet national indoor air quality guidelines, and every unit includes an oxygen depletion sensor. Follow the owner’s manual and local codes.

Do vent-free gas logs produce carbon monoxide?

All gas burners produce some carbon monoxide, but properly adjusted vent-free logs produce very low levels. Keep logs positioned correctly, have the unit serviced yearly and install CO alarms.

Why do vent-free gas logs sometimes smell?

A light odor is normal for the first few hours while paint and logs cure. Persistent odors can come from dust, household chemicals or misplaced logs; clean the unit and contact a service technician if the odor continues.

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