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The Real Risks of Fire

By Jay Whimpey, PE, TACDA Board Member

firemen at housefire

Fire Safety and Survival

There are over 360,000 house fires in the United States every year with a substantial number of injuries and deaths. Eighty percent of the deaths and injuries occur in residential structures, with most of those fatalities occurring while those people are asleep. We can reduce the risk of death or injuries by fire through understanding how and where fires start and how to prevent the fires and ensure prompt notification if a fire occurs.

Studies of fires during emergency situations show a substantial increased risk because of the frequency and severity of fires when individuals and families are using cooking and heating methods that are less familiar and more hazardous than they normally use. The principles and methods for preventing fires and protecting ourselves apply both in our everyday lives and emergency situations.

Asphyxiation, or lack of oxygen, causes most fatalities in fires. A fire is dangerous because of the direct exposure to heat and flames that can burn us, super-heated air that can damage the lungs and breathing passages, inhalation of toxic smoke and gases, and simple lack of oxygen. Calculations show that a typical house with 2000 square feet of living space with 8-foot ceilings has 16,000 cubic feet of air and 20.8% of that air by weight is oxygen. At normal conditions, there is roughly one pound of air in 13 cubic feet. So, there are about 1,230 pounds of total air and about 260 pounds of oxygen in the house. If a fire starts and begins to use that oxygen to support the combustion, it only has to use about half of the oxygen before a human would be largely incapacitated and incapable of escape due to lack of oxygen. A human will lose consciousness and die when an additional 5% of the oxygen is gone. When most materials or fuels burn, they use roughly two pounds of oxygen for each pound of fuel. This includes most carpets, plastics, and wood furniture. So, a fire only has to burn 65 pounds of fuel before it is impossible for people in the house to save themselves from the advancing fire. That corresponds to the weight of a single piece of relatively small furniture or a moderate section of carpet.

In an underground shelter that is 10-feet in diameter and 50-feet long there is only 4000 cubic feet of air and it would only take 16 pounds of fuel burning to make the entire shelter deadly to any occupants.

Studies have indicated the average house today can overwhelm the inhabitants by asphyxiation in roughly two minutes once a fire starts because of the fast burning nature of many of the materials that we use for making carpets, furniture, and electrical appliances. The cotton, wood, and wool that we formerly used to make carpet and furniture have been replaced by nylons, polyesters, and other plastics that burn much more readily. The solid wood that was formerly used in furniture has been replaced by plywood and particle board which contain a substantial amount of highly combustible glue or resins. Prompt notification of a fire, especially when we are asleep, is critical to survival.

Fire Prevention and Elimination

The most common type of fire in the home is caused by cooking on a stove top. Of course, most of the fires are small and can be contained quite easily. The fire inside a pan can be snuffed immediately but we should remember to keep a pan lid within easy reach while cooking. A small fire blanket is another option for fires that have spread beyond the pan but are still contained on the cook top. The use of salt or baking soda is also useful but we should be careful not to spread the flaming materials while applying the salt or baking soda. Other combustible powders such as wheat flour or sugar will feed and spread the fire. A fire extinguisher is also useful but can possibly spread the fire if not used properly. The cook top should always be attended to prevent small fires from growing.

Electrical appliances can also be the source of a fire. A loose electrical connection where the resistance at a connection can generate heat and start a fire on the wiring insulation and surrounding combustibles. A short in the power supply or transformer can also create heat and start a fire. The fires that may have been largely contained in the steel case of the appliances in the past are now able to spread to the plastic on circuit boards and electrical leads and then on to the plastic housing. It reduces risk to unplug appliances when not in use and reducing the overall number of appliances that we use. For example, we should carefully consider whether we need an electric can opener. Such appliances have started fires before.

The use of candles, lanterns, and heaters with a live flame should be minimized and such devices should never be left unattended. Fuel should be stored in a separate area and the fuel should not be added to the devices when they are hot. Fueling should preferably be done outside.

Electrical outlets should not be overloaded and the connections on power strips and other electrical distribution equipment should be cleaned regularly. The dust buildup behind cabinets and entertainment centers where there are electrical connections should be cleaned to control dust buildup. Inspect electrical connectors for signs of heat or poor connections.

The storage of fuels and other chemicals in the garage or utility areas of the house should be minimized. The dryer vent and dryer itself should be cleaned regularly to clear lint and other combustibles. The storage of combustible materials in the laundry and utility areas of the house should be minimized.

Bathroom fans should periodically be cleaned and inspected.

Fire Response

It should be emphasized that the primary responsibility of everyone in the house is to get out of the house as quickly as possible if there is a fire. To that end, an escape plan should be prepared that includes designating multiple escape routes for every room in the house, a single meeting area outside the home, and plan to notify the emergency response personnel. It is important to discuss and demonstrate the plan for younger members of the family and make sure they can actually open windows and exit the window openings if that is part of the plan.

Proper equipment should be stationed at appropriate areas such as fire extinguishers near the doors. Fire blankets should be provided near the kitchen for smothering kitchen fires and other fires where appropriate. A wooden bat or similar tool should be provided to help open windows where appropriate. A fire can create a significant vacuum draft in a home when it finds a place to vent and that can put a negative pressure on widows, making them difficult to open. Thus, a wooden bat for breaking the windows, if necessary, should be stationed near the windows designated for escape. A step stool near the window can help to egress the window and a flexible ladder for the outside of the window, if the window is on the second story of the structure, are also advisable. Special locator stickers should be placed on bedroom windows to notify emergency responders or even neighbors where people in the house normally sleep. The stickers can save time in rescuing the people in the house by directing the response to the right rooms.

Fire Alarm Equipment

The most important pieces of fire equipment for protecting the people in the house are the smoke, heat, and carbon monoxide detectors. The people in the house must rely almost entirely on the detectors while they sleep. As stated earlier in this article, the lack of oxygen kills or incapacitates most victims in their sleep and they die in their beds with no chance to escape.

The most disturbing information about the common smoke detectors in most homes is that they do not work in a timely fashion in many actual fires. The documentation that accompanies most ionizing smoke detectors indicate that they will not work in up to 35% of all fires. There is also a substantial amount of information enumerating the situations and types of fires where the detectors would not be expected to work that seem designed to limit the amount of liability for the manufacturers.

Actual studies have found that the ionizing smoke detectors do not work in roughly 55% of actual fires. They do work many times when the toaster burns a piece of toast or when food is broiled leading to a false sense of security, but when it comes to a real fire burning the actual furnishings or carpets in a house that produce fewer larger particles than when the toast burns, they do not warn the occupants in the structure in time to allow them to escape. Please refer to a short video on YouTube called “When Seconds Count” for some additional information and accounts of testing and actual fires where the smoke detectors failed to provide adequate warning.

To corroborate the findings of several other studies, I conducted some testing on available fire alarms from three different manufacturers. Two ionizing smoke detectors and one combination ionizing smoke detector and CO detector were subjected to some informal testing. Fires with various fuels such as wood, particle board, carpet, and electrical cords with vinyl insulation were established in a portable fire pit about 30 inches in diameter. All three detectors were placed in the smoke plume about 36” above the fire for a period of up to two minutes. The results varied but there were several instances where the detectors failed to trigger when placed directly in the smoke plumes. Even the newest smoke and CO detector failed to trigger after a full two minutes in the electrical cord fire that had the most noticeable black smoke. All the detectors triggered in at least some of the tests after being in the smoke for only 10 seconds which added some validity to the test method, but the findings confirmed that the results were varied and the smoke detectors were not entirely reliable.

There are optical smoke detectors on the market today that are substantially more reliable than the ionizing smoke detectors in most homes. They have been manufactured since the 1970’s and there has never been a fatality from a fire where they have been employed. Applied Fire Technologies of Coppell, Texas manufactures a line of smoke, carbon monoxide, and heat sensors that network together so that every alarm on the local network sounds when one alarm is triggered, thus alerting everywhere in the home. The units have permanent batteries that last for up to 20 years and they run internal diagnostics continuously to ensure that they are operating correctly. They are normally installed by a company representative after an on-site review of each home. You can contact the company and find your local dealer by going to http://www.crossfirealarms.com and going to the “contact us” tab.

Fire extinguishers can be very useful once you have been alerted to a fire but they must be kept in good working order. They are normally fitted with a pressure gauge but they should also be checked to ensure that the powdered fire-retardant material has not solidified. The condition of the fire retardant can be checked by testing the weight balance when the fire extinguisher is gently turned on the side and most of the retardant should be at the bottom. Then the extinguisher can be pushed on its side from a vertical position on a soft carpeted surface. If the horizontal weight balance changes substantially after the “fall” on its side then it can be assumed that the retardant is still loose inside and the fire extinguisher has a high probability of working appropriately when required.

Summary

The images we see on television and in the movies with bright flames of a house on fire with people moving around inside the house and trying to rescue someone are very misleading. Most actual house fires create an environment with thick smoke so that you cannot see anything and acrid and toxic smoke, where an individual cannot maintain consciousness for more than a few seconds. We need to prepare to survive by minimizing the risk of a fire starting with installing the appropriate alarm equipment in place to ensure that we can escape during the early stages while it is possible.


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