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Prior to 2003 most gas water heaters had an open combustion chamber which allowed the owner to relight the pilot with a match. This presented a danger as hot water heaters in areas where other combustibles such as gasoline or propane caused spontaneous combustion and were a risk to your home and safety.

Residential water heaters manufactured after 2003 are “F.V.I.R.” (Flammable Vapor Ignition Resistant) compliant. For the most part, this means that the combustion chamber is now sealed. In order to light the water heater, you must use the pilot mechanism and you can no longer use a match.

Due to this change, new water heaters are significantly safer than water heaters manufactured before 2003.

Effective July 1, 2003, all water heater manufacturers are required to build their 30,40 & 50 gallon atmospheric vent water heaters to new government standards. The American National Standards Institution (ANSI) have established these new standards to prevent accidental or unintended ignition of flammable vapors, such as those emitted by gasoline.

By July 1, 2005, the ANSI Z21.10.1a-2002 standard will apply to virtually all gas fired residential water heaters with BTU ratings of 75,000 and below.

How do FVIR Water Heaters Work?

All water heater manufacturers came together in cooperation with the Consumer Products Safety Commission to form a Joint Research and Development Consortium. The Consortium agreed upon three basic principles of the F.I.V.R. program:

  • A one way intake system to control the intake of make up air into the combustion chamber
  • A flame arrestor plate to provide a one way path for air to travel through
  • A sealed burner compartment door and assembly to create a sealed junction with the combustion chamber

Air enters through the one way intake system, passes through the flame arrestor plate, and normal combustion occurs in the sealed combustion chamber. In the event that flammable vapors are introduced, the vapors are drawn into the combustion chamber where they ignite in the sealed environment. Due to the flame arrestor plate, the flames are contained within the combustion chamber and cannot escape back out of the heater. Most manufacturers have built in additional features that shut off the flow of gas and seal off the combustion air in the event of a flammable vapor event