File: Health and Safety 3 5/77/20M"Residential fires and their life loss have become a significant problem throughout the U.S. The National Fire Protection Association (NFPA) estimates that fires in the U.S. kill 12,000 persons each year and result in injury to several thousand more. Dwelling (residence, apartment and mobile home) fires in Missouri accounted for $23,307,408 in property damage and 45 lives lost according to the 1975 Missouri Fire Marshal's annual report."--First page.David E. Baker (Rural Safety Specialist, Department of Agricultural Engineering), Bob M. Gassaway (Senior Research Technician, University Wide Rural Development), Bill Westhoff, Jr. (Coordinator Fire Training, University of Missouri-Columbia

Baker, David E.

Gassaway, Bob M.

Westhoff, Bill

University of Missouri: MOspace

Stie11te 1111d ~e,1t110!01f1 GUIDE e ~ -f z ~ ~ G'T•f' Staff' 11 tie, Ca•,w• u M C P116/islted /,fl tlte ll11iversilfl of ,Missouri - eot11111/,i11tKte11sio111Jivisio11~oUcAl\~ Home Fire Detection David E. Baker, Rural Safety Specialist, Department of Agricultural Engineering; Bob M . Gassaway , Senior Research Technician, University Wide Rural Development; Bill Westhoff, Jr ., Coordinator Fire Training, University of Missouri-Columbia Residential fires and their life loss have become a signifi-cant problem throughout the U.S. The National Fire Protec-tion Association (NFPA) estimates that fires in the U .S. kill 12,000 persons each year and result in injury to several thousand more. Dwelling (residence, apartment and mobile home) fires in Missouri accounted for $23,307,408 in property damage and 45 lives lost according to the 1975 Missouri Fire Marshal ' s annual report. The majority of fires start from smoking or smoking materials, and almost half the time bedding and upholstery are the first items to ignite (Figure I). 60 56.0% Other Matl's 2.5% ----- -Clothing 3.7% 50 ------40 Upholstery 23.8% 30 -----20 Bedding 26.0% 13 .8% Materials __ :L.31£ _ IO - Buildings 4.0% -----Flammable Liquids 6.5% Smoking Heaters 7.5% , .. .°..'.h':'.. ~2~. l Fixed Wiring 4.3% Electrical 7.0% Cooking Stove I I 4.3% Arson So urce : N FPA No. F R 72- 1, " A Study of Res ide ntia l F ire s, " 1972 Figure 1. Major causes of fires. 11.5% All Other Sources Figure 2. Where fires start. Where and When Do Fires Start? A N FPA study of 400 residential fires that caused 1,301 fatalities indicates that 70 per cent of fires originated in the living room, kitchen and basement (Figure 2) . This study also showed that there is little difference between night (46%) and day (56%) in regard to when fires start. The story is quite different when you look at multiple-death fires (those fires which result in three or more fatalities) . The chance of multiple life loss is three times greater in dwelling fires than in fires in other types of occupancies . About 83 per cent of multiple-death fires occur between 8 p.m . and 8 a .m. , when people are asleep and unaware of development of a fire until it is too late . Fire officials estimate that 50 per cent of life loss due to dwelling fires could be saved by installing early warning fire detection devices . 1907 Archive version - check for updatesChoosing an Early Warning System Home fire detection systems come in basically two types: heat and smoke detectors. The "basic" home detection system will rely heavily on the use of smoke detectors. Smoke detectors typically consist of a sensing chamber, alarm sounding device and the electrical power transmission means. Home smoke detectors come in two types: ionization and photoelectric. Ionization. The ionization smoke detector uses a radioac-tive source (typically Americium-241, an alpha emitting radionuclide) to ionize the air within the sensing chamber. The ionization of air by the radioactive particle causes a very small electrical current flow . When smoke from a fire enters .the chamber, its presence causes a reduction of the current flow. The reduced flow is sensed by the appropriate elec-tronic circuitry, which in turn triggers the alarm horn (Figure 3). Photoelectric. Photoelectric smoke detectors use the principle of scattered or reflected light to indicate the pre-sence of visual smoke (similar to the automatic eye used to open doors). Under no smoke conditions the chamber is dark , and the light shines across the chamber and is received in a light trap on the far side. When smoke is present in the chamber, a photocell located at right angles to the light source senses the light scattered off the smoke particles and, at a suitable illumination level, triggers the alarm horn (Figure 4). Both types of detectors work on the principle of sensing the presence of smoke. The photoelectric detector senses the large smoke particles-those in the visible range. The ion chamber detector senses the small particles-those in the nonvisible range. If a fire starts as a slow smoldering fire (upholstery) with-out any flame, a good photoelectric unit would be superior to a good ion chamber detector in terms of detection time. Con-versely, if flaming is present in the fire, a good ion chamber will detect it faster than a good photoelectric detector. For this reason it is a good idea to use both in your detection system. The other type of home fire detection system is the heat detector. Heat detectors are available in two types: fixed temperature and rate-of-rise. Fixed Temperature Detectors. These are preset to sound an alarm when the air temperature exceeds the "fixed" temperature. The most popular fixed temperature detectors used in homes are preset to sound an alarm when the temperature exceeds 135° F. Other units are available to be preset up to temperatures of approximately 200-225° F. These may be used in an attic where summer temperatures normally may reach 135° F. Rate-of-Rise Heat Detectors. These sound an alarm when the temperature in the immediate vicinity exceeds the preset rate of degree rise per time factor (minutes, etc.). Power Sources To protect the purchaser and establish criteria for the manufacture and installation of home fire detection systems, the National Fire Protection Association has developed NFPA No. 74-Standard for Household Fire Warning Equipment. NFPA Code No . 74 requires that AC (home current) powered units must meet the following conditions: • Power supply must be sufficient to operate the alarm signal(s) for at least four consecutive minutes of at least 85 decibels. • A visible "Power On" indicator must be provided. • All electrical systems designed to be installed by other than a qualified electrician shall be powered from a 1907 ELECTRICAL + POSITIVE ELECTRODE POWER SOURCE NEGATIVE ION ,1~,, lf ALPHA - - - '<'I SOURCE ___ -::.-,;:i ..-;:::1 ,., f ~ --:-;;-/1 POSITIVE ION I :,,-, ALPHA PARTICLES - NEGATIVE ELECTRODE CURRENT DETECTOR Figure 3. Circuit of an ion chamber detector. Combustion particles reduce electrical flow and trigger the alarm. LIGHT SOURCE Figure 4. Sensing chamber in a photoelectric smoke detector. Smoke particles deflect the light beam and trigger the alarm. source not in excess of 30 volts and meeting the requirements for power limited fire protective signaling circuits as defined in Article 760 of the National Electric Code No. 70. • The power source for the unit must not be subject to loss of power by a wall switch. • Neither loss nor restoration of the primary power shall cause an alarm signal. NFPA Code No. 74 requires that battery operated units meet the following requirements: • The alarm must be capable of producing an alarm signal of 85 decibels for four consecutive minutes. • The batteries must meet all power requirements for at least one year including routine testing. • A distinctive audible trouble signal must be given at least once per minute for seven consecutive days before the batteries are incapable of operating (from aging, terminal corrosion, etc.) the device for alarm purposes. • The unit must also be capable of producing the alarm signal for four consecutive minutes during the seven days of trouble signal. Battery operated smoke detectors have two advantages and one disadvantage when compared to detectors operated from the dwelling's electrical power. One advantage is that if the electrical power in the dwelling should be off due to an interruption from the utility company or from a fire within the dwelling, the detector will sti ll function. The other advantage is that you can install a smoke detector in an existing dwelling where an appropriately placed electrical outlet is not available. The major disadvantage is that the batteries will need to be replaced once a year. Location The "basic" minimal detection system should consist of one smoke detector outside of each sleeping area and one additional smoke unit on each additional living level, includ-ing the basement and excluding unfinished attics, crawl spaces, etc. If hallways are longer than 40 feet between the sleeping area and living area, two smoke detectors should be used. Heat detectors or additional smoke detectors may be considered by the home owner as a supplement to the basic system. Areas that might be considered for additional heat detectors are the kitchen, dining room, furnace room , attic, garage , etc . A good system should include both types of smoke detectors--one plug-in photoelectric detector and one battery operated ionization detector. A family might consider install-ing a photoelectric unit in tile bedrooms of any family members who smoke there. Mounting One should follow the manufacturer's recommendations for mounting and servicing the detectors. Locate the first unit (ionization) in the center of the hallway ceiling between the bedrooms and the living area not closer than 12 inches away from the wall (Figure 5a). Additional locations should be determined by the family's life style. If a person must wall-mount the detector, it should be mounted no closer than 6 inches and no farther. than 12 inches from the ceiling (Figure 5b). This is to avoid the dead air space. Mobile home owners may want to consider wall mounting their units on an "inside" wall to avoid some of the problems of ceiling drafts . Home owners should not locate smoke detectors in the following areas: • Kitchen-false alarms (burned food, etc). • Garage-temperature extremes and false alarms . • In front of air registers (also open windows or open doors) may create false alarms due to high air velocities . • Attics, bathrooms, inside air ducts, unheated buildings, unheated motor homes-may exceed typical tempera-ture limits 32° F to 100° F. Buying Tips With the advent of modem electronic circuitry in mina-ture, the single station smoke detector has become the subject of strong sales rivalry by several companies vying for the household market. The result is that some sales personnel are using high pressure tactics. · Therefore, it is wise for the potential purchaser of a home fire alarm system to be cautious. Here are some buying tips : • Don ' t be frightened into a quick purchase. Some door-to-door salesmen use films, pictures and tape recordings which trade on your emotions. Get at least two or three price estimates from different manufactur-ers before purchasing. • Test the units as you install them, or if you elect to have someone else install the units , request that the installer test the units in your presence . • Request an instruction booklet that gives you informa-tion on operation, testing and maintenance of the alarms. • Buy only fire alarms which carry labels showing they have passed the tests of the Underwriter Laboratory (UL) or Factory Mutual (FM). • Understand the guarantee or warranty with the unit you select, and be sure you understand who will repair or replace the unit if it proves defective . Figure Sa. Ceiling mounting. IT ACCEPT ABLE HERE { 12" _J_ Figure Sb. Wall mounting. An Escape Plan Your job is not done, however, when you buy and install smoke detectors. There remains the task of training your family to respond properly when a fire alarm is sounded. The first thing to do is to develop a family plan for escape. It is a good idea to make a floor plan with two escape routes. STEP A (basic floor layout): I. Make an outline of the entire floor area. Dimensions and details need not be exact. 2. Now add each bedroom and label it. 3. Locate windows, doors and stairway. On upper floors , shade in any rooftops that could be used as a fire escape. STEP B (room inspection): I . Go to each bedroom. Select the best window for an emergency escape. 2. Test the window to see that it works easily . .. and is large and low enough. STEP C (complete "Escape Plan"): I . Black arrows show normal exit through hall or stair-way. 2. Colored arrows show emergency exit in case fire blocks hallway or stairs. Every member of the family should have at least two escape routes from his or her bedroom. One usually will be by the door into the hallway , and the other route usually will be by the window. 1907 For two-story homes, it probably will be necessary to provide a chain ladder (the first choice) or a rope ladder to escape. Again thiSTequires training because the person using the ladder must make certain he or she is not going to be crawling past a life threatening fire on a lower floor and must know how to use the ladder. Every member of the family should know exactly what he or she is expected to do in the event of a fire. This can be accomplished by holding family fire drills. The first thing to be taught is that no one should jump from bed and stand up when the alarm sounds. Instead all family members should learn to crawl out of bed onto the floor. In the early stages of a fire, the toxic and super heated fire gases lie in layers near the ceiling, and it is imperative to stay below these gases. There have been many cases in which it appears that victims slept through the build-up of these gases, only to die when they stood up and inhaled the deadly gases. Each family member should crawl to his or her bedroom door. If the door is closed, he should feel the door. If the door is not hot to the touch, it is probably safe to place the weight of his body against the door and open it slowly to see if smoke and flames have filled the hallway. Body weight should be used to keep the door from rapidly opening in the event that there is heavy smoke or fire in the hallway or an explosion of fire gases . If the hallway appears to be clear, the first member of the family into the hallway then can crawl from one bedroom to the next to insure that all inembers of the family are awake. The hallway and nearest outside door should be used for escape ONLY if you are very certain that no flames are visible and there is little or no smoke along the path you must travel. The family should select a meeting place for all family members outside the home near a tree, mailbox, etc. Every-one should go immediately to this meeting place; when every-one is accounted for, someone can be selected to go to a neighbor's home to call the fire department. When calling the fire department, speak slowly and distinctly so that you are sure the fire department understands whose house is on fire and where it is located. In fact, you should practice giving directions to your home, the same directions you would give to a visitor who has never been there before. Once everyone is out of the house , no one should return . More than one person has been killed by going back into the fire to save a few dollars worth of keepsakes . ST A Y OUTSIDE! Obviously , learning the fire escape plan is like learning anything else-you get better at doing it if you practice . Periodically, preferably once a month, someone in the family should sound the alarm in the middle of the night and then monitor the actions of other family members to see that they comply with the fire drill plans. And remember-installation of an early warning fire alarm system combined with a well rehearsed plan for escape may save the lives of you and your family. Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914 in cooperation with the United States Department of Agriculture. Carl N. Scheneman, Vice President for Extension, Cooperative Extension Service, University of Missouri and Lincoln University, Columbia, Missouri 65201. The University of Missouri is an equal employment and educational opportunity institution. 1907 File: Health & Safety 3 5/77/20M 

Home fire detection

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Home fire detection

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