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Ignition of Flammable Vapors and Gas Water Heaters

This Fact Sheet presents information on the role of gas water heaters in household flammable vapors incidents and the overall safety of these important and cost-effective appliances. Over 50 million homes in the U. S. currently use gas water heaters to provide reliable domestic hot water at costs typically less than one-half that of electric water heaters. The following discussion presents questions on the issue of flammable vapors and gas water heaters and provides perspectives on these products and consumer safety. What is meant by the term "flammable vapors?" Flammable vapors can arise from evaporation of flammable liquids due to accidental spills or misuse in the home. These vapors, usually heavier than air, can accumulate as flammable concentrations over time and spread beyond their liquid source. Upon contacting an ignition source such as an open flame, a spark, or a hot surface, vapors can ignite to cause a fire or an explosion. Generally speaking, the more easily the flammable liquid evaporates, the greater its potential for producing flammable vapors. As a result, spills of gasoline is of prime concern. How frequently are natural gas water heaters involved in ignition of flammable vapors in homes? According to the U. S. Consumer Product Safety Commission (CPSC), gas fired water heaters igniting flammable vapors in homes have been associated with slightly fewer than 2,000 fires per year, resulting in 17 deaths and 316 injuries for all years up to 1 1994. These statistics include both natural gas and propane fueled water heaters. However, only 5% of fires involving ignition of flammable vapors in homes 2 are related in some way to gas water heaters. These incidents occurred across the population of over 50 million homes with gas water heaters. Flammable vapor ignitions for the other 95% of incidents represent a variety of other ignition sources and consumer activities. While the consequences of a flammable vapors fire can be tragic, gas water heaters are associated with a small fraction of flammable vapor ignitions and are involved with a very small percentage (approximately 0.15%) of total household fires.

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What are the sources of flammable vapors involved in house fires? According to CPSC, more than 75% of flammable vapor incidents involving gas water heaters are due to spills of improperly stored gasoline or improper indoor use of gasoline. Improper handling of gasoline includes storage indoors, which in most jurisdictions in the U. S. is prohibited by local fire codes and in many locations is against the law. In addition, gasoline stored indoors has sometimes been stored next to water heaters in basements or in utility closets. Improper use of gasoline has included use as a solvent for cleaning household items and automotive parts. Other sources of flammable vapors include a variety of solvents (e.g., volatile paint strippers and related chemicals) used improperly such as without proper ventilation. Safety precautions to avoid flammable vapor ignition incidents are commonly listed on the solvent container by the manufacturer. What current codes and standards help protect consumers from water heater caused fires? As discussed above, most local fire codes and many local laws prohibit storage of gasoline indoors other than in garages. The voluntary consensus standard for residential gas storage water heaters, Z21.10.1 which is recognized by the American National Standards Institute (ANSI), requires a label on the water heater storage tank regarding avoiding storage and use of flammable liquids in the vicinity of gas 3 water heaters (see Figure on following page). The label also calls for elevating the water heater in areas where flammable materials are stored or used so that the burner and pilot flames are at least 18 inches above the floor. As the label states, this requirement is intended to reduce, but does not eliminate, the risk of flammable vapors ignition. The National Fuel Gas Code (NFGC) prohibits the installation of gas appliances (including water heaters) in areas where the open use, handling, or dispensing of flammable liquids

"CPSC Splits Vote on Gas Water Heaters," News from CPSC, Release #95-043, December 15, 1994. 2 ibid.

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"Gas Water Heaters: Volume 1, Storage Water Heaters with Input Ratings of 75,000 Btu Per Hour or Less," ANSI Z21.10.1-1998/CSA4.1-M98.

occurs, unless the design, operation, or installation reduces the potential of ignition of the flammable va4 pors. The NFGC also requires that gas water heaters in residential garages be installed so that all burners and burner ignition devices are located not less than 18 inches above the floor, except where appliances are installed in separate, enclosed space and where 5 combustion air is taken from outside the garage. These national codes and standards, combined with consumer awareness of flammable vapors hazards and adherence to instructions for use of flammable liquids would, in most cases, substantially eliminate the risk of flammable vapors ignition and its consequences. What has been the involvement of consumers in flammable vapors ignition events? Consumer misuse of gasoline and other flammable liquids is the major source of risk of ignition of flammable vapors, regardless of the ignition source. As discussed above, consumer activities such as improper storage and use of these materials or use without manufacturer-recommended precautions has been a major contributing factor to ignitions. In response to this aspect of incidents, the Gas Appliance Manufacturers Association (GAMA), working with the National Fire Protection Association (NFPA), produced an extensive consumer education program to increase consumer awareness of flammable liquids hazards in the home and to encourage safe use of household chemi6 cals. Are changes needed in gas water heater design? While CPSC has determined that current 7 water heater designs are not unsafe, water heater manufacturers are trying to incorporate flammable vapor ignition resistance technologies into new models. To that end, the manufacturers have worked through the Z21.10.1 national consensus standard process for gas water heaters to add a test procedure to the current standard for product certification to test the flammable vapor ignition resistance of gas water heater designs. This test procedure will be effective in the near future so that all gas water heaters submitted for approval under the Z21.10.1 consensus standard will be tested for resistance to ignition of flammable vapors. Are natural gas water heaters available that mitigate ignition hazards? Currently, a limited number of models of gas water heaters are advertised as designed for flammable vapors ignition resistance. In the near future, with the promulgation of revisions to

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the ANSI standard for flammable vapors ignition testing, more models are expected to be brought to market. Up to date information on models and manufacturers of gas water heaters with this feature is available from GAMA (contact information is available through the GAMA website: http://www.gamanet.org). What should consumers do? First and foremost, consumers should not store highly flammable liquids such as gasoline indoors, except in limited quantities in garages. In addition, gasoline should never be used for cleaning purposes anywhere indoors. Gasoline and other flammable liquids should be stored in proper containers with appropriate, tamper-resistant caps. All flammable liquids should be used according to manufacturers' instructions provided on their containers. Consumers should make sure that their water heaters are installed according to the manufacturer's instructions and local codes. In garages, this typically means that ignition sources in water heaters (burners and pilots) should be elevated 18 inches from the floor. Consumers should consult with their local fire department, gas utility, or appliance installer for other requirements in their area. With compliance to local requirements and proper handling and storage of flammable liquids, flammable vapor ignitions and fires involving gas water heaters are a remote possibility If consumers think that a flammable vapor ignition resistant gas water heater is right for them, they should consult with local installers or retailers or GAMA to identify available water heater models that offer this feature.

National Fuel Gas Code: 1999 Edition, ANSI Z223.11999/NFPA 54-1999, Section 5.1.8. 5 ibid, Section 5.1.9. 6 [GAMA campaign citation] 7 "CPSC Splits Vote on Gas Water Heaters," News from CPSC, Release #95-043, December 15, 1994.

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