Their technical name is Flammable Vapor Ignition Resistant (FVIR) water heaters. The basic idea behind the design is to prevent flammable gases, such as paint thinner, gasoline, or other household chemicals from exploding and catching the home on fire if they are in the vicinity of the water heater's pilot light. This new FVIR design allows the combustion air into the base of the tank, but not back out. If a vapor ignition occurs, only the vapor inside the base of the tank will burn. The flammable vapors outside the tank will not catch fire.
The new FVIR design also has a sensor on the inside of the base of the tank that shuts off the gas supply if an explosion occurs. This sensor is glass and a one-time use only device. If the water heater has a vapor explosion, the glass breaks triggering the gas to shut off. However, if this occurs, you can't simply replace the glass sensor. You have to replace the entire water heater.
This would probably help discourage the storage of flammable liquids in the house and basement.
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