Fire Understanding

The Phenomenon of Fire

Fire is the visible heat energy being released from rapid oxidation of afuel.  Something is
'on fire' when the exothermal release of heat from the oxidation reactionreaches visible light level.

Basically, combustion takes place within two modes-flaming andflameless. The flaming mode can be viewed as a tetrahedron, with each siderepresenting one of the four basic
components of flaming combusion: fuel, heat, oxygen and uninhibited chainreaction. Here the practical emphasis is on extinguishing an existingfire.

The classic fire triangle illustrates the flameless mode, the three legsrepresenting fuel, oxygen and heat. Air provides oxygen forcombustion. The heat required for ignition varies with the characteristicsof the fuel. Fuel is any substance that will sustain combusion after theinitial application of heat to start it. Here the practical emphasis is onpreventing a fire from starting by prohibiting the formation of thetriangle.    

How Flammable Liquids Safety Equipment Defeats Fire

Safety equipment for use in storing, transporting or dispensingflammable liquids is designed to control one or more of the legs of the FireTriangle.

Containment of the liquid fuel to prevent it from spreading in event offire is a primary function of all safety containers. These containers includesafety cans, rinse and wash tanks, bench and plunger cans, rinse and washtanks, bench and plunger cans, drip cans, storage cabinets, waste containersand others.

Dissipation of heat to prevent flammable liquid vapor from reachingignition temperature is another function built into certain types of safetyequipment. This is accomplised by the flame arrester which is common tosafety cans and faucets, bench cans and other equipment. The flame arrester, inthe form of a wire mesh screen or perforated baffle plate, permits escapingvapor to burn but dissipates heat so that vapor inside the container will notignite or explode.

Closing out oxygen is still another function of certain safetycontainers. For example, when the lids of self-closing rinse and cleaningtanks shut, they snuff out fire by closing off the oxygen supply.

Characteristics of Flammable Liquids

In order to best understand the hazards of flammable liquids and thecontrol procedures and to interpret the tabular material, the followingdefinitions will prove useful.

Underwriters Laboratories, Inc., Flammability Hazard Classification.

In addition to the NFPA, this is also a system for grading the relativeflammability hazards of various liquids. This is a useful classificationbecause actual hazard in use of a flammable liquid is dependent on a number offactors in addition to flash point. These are the UL classes of relativeflammability hazards:

Ether : class 100 (max hazard)
Gasoline : class 90-100
Alcohol (ethyl) : class 60-70
Kerosene  : class 30-40
Paraffin Oil : class 10-20

Classifications, Flammable and Combustible Liquids.  

A flammable liquid is one having a flash point below 100 degree F andhaving a vapor pressure not exceeding 40 lb/sq in. absolute at 100 degree F. Acombustible liquid is one having a flash point at or above 100 degree F.

Vapor. In any liquid there is a constant movement ofmolecules. As temperature increases, the molecules speed up, someacquiring enough energy to escape from the liquid surface as a vapor.When vaporescapes from a flammable liquid into the air, a flammable or explosivesituation can occur, dependent upon the proportions of the air/vapor mixture.

Flash point is the lowest temperature of a flammable liquid at which itgives off vapor sufficient to form an ignitable mixture with the air near thesurface of the liquid or within the vessel used. Combusion is not continuous atthe flash point. Flash point is the basic characteristic used by NFPA toclassify the relative hazards of liquids.

Ignition temperature is the minimum temperature to which flammableliquid vapor in air must be heated in order to initiate or cause self-sustainedcombustion independently of the original heat source.One might tend to discountthe high hazards of flammable liquids when noting the relatively high ignitiontemperatures (gasolines, for example, are in the 500 to 800 degree Frange). But what must be recognised is that an extremely small area andduration of temperature contact is all that's needed to set flammable vaporaflame. A static spark with the duration of a few thousandths of a second,contacting a few molecules of the vapor/air mixture is enough to raise thetemperatures above the ignition point.

Flammable (explosive) range of flammable liquids is the percentage rangeof liquid vapor in air, by volume, within which ignition canoccur. Gasoline, for example, has an explosive range between 1.4% and7.6%. This indicates that any concentration of gasoline vapor in airbetween these percentage limits will ignite at any temperature above -45 degreeF (flash point) when an ignition source provides a contact temperature in therange of 500 degree to 800 degree F (ignition temperature, depending on type ofgasoline). Auto engine carburetion is designed to keep the gas/air mixturefed to the cylinders within this explosive range. Too 'lean' a mixture (near orbelow 1.4%) or too 'rich' (at or above 7.6%) causes engine firing failure orfaulty operation because the gasoline vapor/air mixture is at the limits of theexplosive range.

Explosive range figures are based on normal atmospheric temperatures andpressures.  There may be a considerable variation in explosive range whereother temperatures and pressure are present. Increases in temperature willwiden the explosive range.  Pressure differences depend on theflammable liquid involved but substantial vacuum (pressure decrease) willgenerally narrow the explosive range.

Specific gravity of flammable liquids is important in fire preventionplanning to anticipate behavior of hazardous materials where water or otherliquids are present under fire conditions. Many flammable liquids withspecific gravity below 1 (lighter than water) are also insoluble inwater. In the event of fire with such liquids present, water may beineffective as an extinguishing agent.

Water solubility refers to the degree to which a flammable liquid issoluble in water. This is useful in determining effective extinguishingagents and methods. Alcohol-resistant type foam, for example, is usuallyrecommended for water soluble flammable liquids.

Vapor pressure of liquids is below 40 pounds per square inch absolute,at 100 degree F, by definition. Materials with higher vapor pressures aredefined as gases at 100 degree F to establish a convenient technical separationbetween the two forms of matter. Vapor pressure is the pressure exerted byvapor above the surface of a liquid in a closed container. It is caused byevaporation and is stabilized by confinement in a closed container to apressure characteristic of the specific liquid.As temperature increases, thevapor pressure of a liquid increases. At the point where the vaporpressure equals atmospheric pressure, the escape of molecules from the liquidsurface is greatly accelerated and boiling takes place.

Vapor pressures of flammable liquids are an important consideration infire prevention.They give the relative speed of evaporation: the higher thevapor pressure, the greater the evaporation rate and the more vapor escapepotential every time a safety container is opened.

Boiling point of a liquid is the temperature of the liquid at which itsvapor pressure equals the atmospheric pressure.

Vapor density, as commonly used in fire protection, is the weight of avolume of pure gas compared to the weight of an equal of volume of dry air atthe same temperature pressure.  A figure greater than 1 indicates that agas is heavier than air. This means that any escaped vapor will settledownward onto floors and flow with air currents, around corners and down stairsor elevator shafts to pool in low spots. If the source liquid is open and acontinuous supply of vapor is flowing, a spark anywhere along the vapor trail -perhaps hundreds of feet or several floors away - will set off an explosion andfire that may envelop an entire building almost instantly.

Fire Protection Improve

Australia, -- Standards Australia has released an interim standard to assist fireauthorities in the selection and development of protective clothing forfirefighters. Fire agencies, the fabric technology industry, manufacturers andunion representatives contributed to the development of interim standard AS4967 -- 2001 -- Protective clothing for firefighters -- Requirements and testmethods for protective clothing used for structural firefighting. The recentlyselected New South Wales Fire Brigade uniforms have a garment shell andprotective liner for ease of cleaning and long-term maintenance. They conformto the standard. Two other fire clothing standards have also been released -- AS4824 (Int) -- 2001 -- Protective clothing for firefighters -- Requirements andtest methods for protective clothing used for wildland firefighting, and AS/NZS4821 (Int) -- 2000 -- Firefighters' protective footwear. 

A draft revision of the Standards Australiaportable fire extinguisher standard is expected later this year. Changes toAS/NZS: 1841 -- Portable fire extinguishers, may include the removal of the"E" fire classification when the extinguishing agent is a conductorof electricity, such as water or a conductive aqueous solution. There isconcern about the potential exposure of an operator to electrocution. 

Work continues on a revision of the StandardsAustralia fire maintenance standard. It is anticipated the revised AS 1851 --1995 -- Maintenance of fire protection systems, will be published in the secondhalf of 2002. The existing 16 parts of the standard will be consolidated. It isalso anticipated the standard will be referenced in the Building Code ofAustralia, making it mandatory.

Fire Hazard from Fire Filling Portable Gas Can In vehichle

• In incidents reported to NIOSH in the US, firesspontaneously ignited when workers or others attempted to fill portablegasoline containers (gas cans) in the backs of pickup trucks equipped withplastic bed liners or in cars with carpeted surfaces. Serious skin burns andother injuries resulted.

• These fires result from the buildup ofstatic electricity. The insulating effect of the bed liner or carpetprevents the static charged generated by gasoline flowing into the container orother sources from grounding. The discharge of this buildup to the groundedgasoline dispenser nozzle may cause a spark and ignite the gasoline.

• Both ungrounded metal (most hazardous) and plastic gascontainers have been involved in these incidents, a NIOSH Hazard ID said.

Recommendations for prevention
Construction workers and others in small businesses who often work withgasoline powered equipment commonly use portable gas containers. Homeowners usegas cans for their landmowers and other equipment.

• Avoid the hazardouspractice of leaving the portable gas containers in trucks or cars whenrefueling

• Before filling, remove thecontainers from the vehicle and place them on the ground at a safe distancefrom the vehicle (provides path to dissipate static charge to ground)

• Touch the container withthe gas dispenser nozzle before removing the container lid (provides anotherpath to dissipate static charge to ground)

• Keep the nozzle in contactwith the container inlet when filling (to dissipate static charge buildup fromflow of gasoline)

Additional prevention measures include:

• Manufacturers or retailers- place a hazard label on all plastic liners being sold warning workers not tofill portable gas containers in the bed liner of the truck but always to placethe containers on the ground before filling

• Gas stations - display awarning notice near gas pumps to place all portable gas containers on theground before filling

• Manufacturers - build bedliners that can be grounded to the metal truck, thereby dissipating potentialelectrostatic charge

On Office Fire Prevention Strategies

Learn the location of fireescape routes and how to activate the fire alarm. Participate in practice firedrills on a regular basis. Become familiar with stairway exits - elevators maynot function during a fire, or may expose passengers to heat, gas and smoke.

Through a program of scheduled inspections, unsafe conditions can be recognizedand corrected before they lead to serious injuries. Take a few moments each dayto walk through your work area. Look for items previously pointed out, such asobjects protruding into walkways, file cabinets that are weighted toward thetop or frayed electrical cords. Advise personnel in the area of the hazards andset about correcting them.

• Heat-producing equipment - copiers, work processors, coffee makers and hotplates - are often overlooked as a potential fire hazard. Keep them away fromanything that might burn.

•  Electrical appliances can be fire hazards. Be sure to turn off allappliances at the end of the day. Use only grounded appliances plugged intogrounded outlets (three prong plug).

•  If electrical equipment malfunctions or gives off a strange odor, disconnectit and call the appropriate maintenance personnel. Promptly disconnect andreplace cracked, frayed, or broken electrical cords.

• Keep extension cords clear of doorways and other areas where they can bestepped on or chafed and never plug one extension cord into another.

• Do not allow combustible material (boxes, paper, etc.) to build up ininappropriate storage locations (near sources of ignition).

Emergency Preparedness
One result of the recent trend toward open officeenvironments is that smoke from office fires is not contained or isolated aseffectively as in less open designs. Open office designs allows smoke to spreadquickly and the incorporation of many synthetic and other combustible materialin office fixtures (such as furniture, rugs, drapes, plastic wastebaskets, andvinyl covered walls) often makes 'smoky' fires. In addition to being smoky,many synthetic materials can emit toxic materials during a fire.

For example, cyanide can be emitted from urethane which is commonly used inupholstery stuffing. Most burning materials can emit carbon monoxide.Inhalation of these toxic materials can severely hamper an office worker'schances of getting out of a fire in time. This makes it imperative for officeworkers to recognize the signal to evacuate their work area and know how toexit in an expedient manner.

The local emergency action plan will address potential emergencies that can beexpected in your work area. For emergency evacuation, the use of floor plans orworkplace maps that clearly show the emergency escape routes and safe or refugeareas should be included in the plan.

All employees must understand what actions theyare to take in the work area and assemble in a safe zone. All new employeesshould discuss how they should respond to emergencies with their supervisorsshortly after starting work and whenever their responsibilities under the planchange.

This orientation should include:

Identifyingthe individuals responsible for various aspects of the plan (chain of command)so that in an emergency confusion will be minimized and employees will have nodoubt about who has authority for making decisions.

Identifyingthe method of communication that will be used to alert employees that anevacuation or some other action is required as well as how employees can reportemergencies (such as manual pull stations, public address systems, ortelephones).

Identifyingthe evacuation routes from the building and locations where employees willgather

General guidancefor fires and related emergencies includes:

If you discover a fire or see/smell smoke,immediately follow these procedures:

Notifythe local Fire Department

NotifyCDC Physical Security or Building Security Force

Activatethe building alarm (fire pull station). If not available or operational,verbally notify people in the building.

Isolatethe area by closing windows and doors and evacuate the building, if you can doso safely.

Shut downequipment in the immediate area, if possible.

Ifpossible and if you have received appropriate training, use a portable fireextinguisher to:

assist oneself to evacuate;
assist another to evacuate; and
control a small fire.

Do notcollect personal or official items; leave the area of the fire immediately andwalk, do not run to the exit and designated gathering area.

Youshould provide the fire/police teams with the details of the problem upon theirarrival. Special hazard information you might know is essential for the safetyof the emergency responders. You should not re-enter the building untildirected to do so. Follow any special procedures established for your unit.

If thefire alarms are ringing in your building, you must evacuate the building andstay out until notified to return. Move to your designated meeting location orupwind from the building staying clear of streets, driveways, sidewalks, andother access ways to the building. If you are a supervisor, try to account foryour employees, keep them together and report any missing persons to theemergency personnel at the scene.

If anindividual is overexposed to smoke or chemical vapors, remove the person to anuncontaminated area and treat for shock. Do not enter the area if you suspectthat a life threatening condition still exists (such as heavy smoke or toxicgases). If CPR certified, follow standard CPR protocols. Get medical attentionpromptly.

If youror another person's clothing catches fire, extinguish the burning clothing byusing the drop-and-roll technique, wrap victim in a fire blanket or dousevictim with cold water (use an emergency shower if it is immediatelyavailable). Carefully remove contaminated clothing; however, avoid furtherdamage to the burned area. Cover injured person to prevent shock. Get medicalattention promptly.

Electrical & Fire Safety

Fire and Burn Prevention

• Fires and burnsare the second leading cause of household injuries.  Each year nearly4,000 people in the U.S. die in home fires.  Thousands of others are injuredas a result of fires or accidental burns.  Most of these deaths involvechildren and elderly adults.  Kitchen accidents, space heaters, chimneyfires, faulty electrical wiring, and cigarettes are common causes.  Checkyour home for fire hazards.  Install smoke detectors on every floor.

Tips on Fire Safety

• Dispose of cigarettes, cigars, and matches carefully.

• Install smoke detectors on each floor of your home and test them often.

• Plan two escape routes from each floor of your home and practice usingthem.  Be sure you can open doors and windows from the inside without akey.

• Never leave a burning candle or fireplace unattended.

• Don’t place anything that will burn near a furnace, water heater, spaceheater, or the stove top.

• Don’t use flammable chemicals near appliances with pilot lights.

• Have your furnace and chimney inspected each year.  Some utilitycompanies provide free or low cost inspections.

• Know how to put out kitchen fires.  If a fire occurs, don’tpanic.  For oven fires, close the door and turn off the oven.  Use apot lid to smother a stovetop fire.  Keep a filled ABC-rated fireextinguisher near the kitchen.

• Pay attention when you are cooking.  If you must leave the kitchenturn off all burners.

• Prevent scalds by setting your water heater to 120 degrees or lower. Anti-scald devices are available for bathtubs or showers.

• Know emergency phone numbers for your area.  In most places it is911.  Post the number near each telephone.  Teach children theemergency number.

Tips to Protect Children from Fires and Burns

• Teach children not to play with matches or lighters.  Store them outof sight and reach.

• Teach your children what to do if they smell smoke or hear the smoke alarm.

• Have children practice escaping from a fire.

• Never leave young children alone.

• Place pots and pans on the rear burner of the stove and always turn handlesinward so they are not accessible to toddlers.

• Keep the cords for crockpots, coffee makers, and deep fryers out of thereach of small children.

Electrical Safety

• While enjoyingelectric TVs, radios and other appliances, we may forget they can cause shocksand fires.  In 1990, bad plugs, cords, switches, and outlets caused about13,000 home fires and nearly 200 deaths.  Most electrical fires andinjuries can be prevented.  People should take the time to have theirelectrical systems inspected and learn about electrical safety.

Tips on Electrical Safety

• People who live in homes that are more than 10 years old should considerhaving the wiring inspected.  If your home is more than 40 years old, aninspection is overdue.  Be sure to consult with your local building inspectorbefore making repairs.

• Never place electric cords under rugs or bedding.  Heat or sparks fromthese cords could cause a fire.

• Follow the safety tips on new appliances.

• Check electrical cords for signs of wear.  Replace frayed or crackedcords to prevent shocks and fires.

• Check labels on lamps and use the right size bulb.  Check the label onyour fuse box and be sure you use the right size fuses.

• Fix electrical problems right away.  If fuses blow often, circuitbreakers trip often, switches get hot or people are shocked, something iswrong.

• Cover unused outlets with plastic plugs.

• If a cord has 3-prongs, use it properly.  Don’t remove the extraprong.  The third prong is there because the appliance must be grounded toprevent electrical shocks.

• Take cover during a thunder storm.  If you are indoors, stay away fromopen windows and doors and use the telephone only in an emergency.  If youare outdoors stay in your car and away from water, trees, and metalobjects.  Avoid low areas that might flood in a heavy rain.

• Do not overhaul outlets.  Extension cords shouldn't be used aspermanent fixtures in home rebuilding.

Ground Fault Circuit Interrupters

• A ground faultcircuit interrupter or GFCI is a special type of outlet that preventsshocks.  These outlets are recommended for areas where water isused.  Install GFCIs in bathrooms, kitchens (within 6 feet of the sink),laundry areas, garages, basements, outdoor outlets, and around pools, saunas,and hot tubs.  Test these outlets monthly.

For more information

• Fire Prevention: call your local fire department.

• Electrical Safety: call your local utility or an electrical contractor.