WORKPLACE FIRE RISK AND PREPAREDNESS
Common Work Place Fire Hazards
1. Explosive Substance
● Substance that may cause explosion under the effect
of flame.
2. Flammable Substance
2. Flammable Substance
(Extremely, Highly & Flammable)
● Substance that are flammable based on its
physicochemical properties.
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3. Oxidizing Substance
● Substance that may give rise to highly exothermic in
● Substance that are flammable based on its
physicochemical properties.
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3. Oxidizing Substance
● Substance that may give rise to highly exothermic in
contact with other substance especially flammable
substances.
Selecting Correct Extinguishing Agent
Fire extinguishers are further divided into handheld and cart-mounted, also called wheeled extinguishers. Handheld extinguishers weigh from 0.5 to 14 kilograms (1 to 30 pounds), and are hence, easily portable by hand. Cart-mounted units typically weigh 23+ kilograms (50+ pounds). These wheeled models are most commonly found at construction sites, airport runways, heliports, as well as docks and marinas.
Australia
In Australia, yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted.
Water
Condensed aerosol fire suppression
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Fire Fighting Procedure
1. Identify the chemical hazard before fighting the fire.
2. Refer to the MSDS for correct fire fighting procedure.
3. Observe the chemical reaction information
(during fire, in contact with other material i.e. water, and after fire)
4. Wear approriate PPE.
5. Fight fire using recommended extinguishing agent and method :
a) Starvation method
- Reducing or removing the fuel from the scene of the fire.
b) Smothering method
- Reducing or cutting off the oxygen supply from the scene of fire.
c) Cooling method
- Lowering the temperature or reducing the heat.
There are several methods firefighters use to put out fires. Fire needs 3 things to survive, called "the triangle of fire", heat, oxygen, and fuel. All firefighting techniques remove one of those elements to put out the fire. The first is to spray water or fire retardant on the fire, either using a fire hose or a special aircraft. They smother the fire, removing oxygen, and water cools it. Another method is a fire break. A fire break is a space with no fuel. Therefore, the fire cannot burn past the fire break, and the fire eventually exhausts its fuel and burns out. Those are the two most common ways to put out a fire.
Recent thinking on fires treat them as a four legged stool, now including "chain reaction." Some newer firefighting methods simply break the chain reaction to stop the fire. Chemicals are often used on fires, but the best know way is to use a fine spray of water. Although the water cools the fire (and resulting steam remove oxygen), a spray or even foam can separate the fuel from the air, starving the fire as it rapidly cools.
Selecting Correct Extinguishing Agent
A fire extinguisher, flame extinguisher, or simply an extinguisher, is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not intended for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user (i.e., no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a fire department. Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire.
In the United States, fire extinguishers, in all buildings other than houses, are generally required to be serviced and inspected by a Fire Protection service company at least annually. Some jurisdictions require more frequent service for fire extinguishers. The servicer places a tag on the extinguisher to indicate the type of service performed (annual inspection, recharge, new fire extinguisher) and when.
There are two main types of fire extinguishers: stored pressure and cartridge-operated. In stored pressure units, the expellant is stored in the same chamber as the fire fighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers, nitrogen is typically used; water and foam extinguishers typically use air. Stored pressure fire extinguishers are the most common type. Cartridge-operated extinguishers contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the extinguishing agent. This type is not as common, used primarily in areas such as industrial facilities, where they receive higher-than-average use. They have the advantage of simple and prompt recharge, allowing an operator to discharge the extinguisher, recharge it, and return to the fire in a reasonable amount of time. Unlike stored pressure types, these extinguishers use compressed carbon dioxide instead of nitrogen, although nitrogen cartridges are used on low temperature (-60 rated) models. Cartridge operated extinguishers are available in dry chemical and dry powder types in the U.S. and in water, wetting agent, foam, dry chemical (classes ABC and B.C.), and dry powder (class D) types in the rest of the world.
Fire extinguishers are further divided into handheld and cart-mounted, also called wheeled extinguishers. Handheld extinguishers weigh from 0.5 to 14 kilograms (1 to 30 pounds), and are hence, easily portable by hand. Cart-mounted units typically weigh 23+ kilograms (50+ pounds). These wheeled models are most commonly found at construction sites, airport runways, heliports, as well as docks and marinas.
Australia
| Type | Pre-1997 | Current | Suitable for use on Fire Classes (brackets denote sometimes applicable) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Water | Solid red | Solid red | A | ||||||
| Foam | Solid blue | Red with a blue band | A | B | |||||
| Dry chemical (powder) | Red with a white band | Red with a white band | A | B | C | E | |||
| Carbon dioxide | Red with a black band | Red with a black band | (A) | B | E | ||||
| Vaporising liquid (non-halon clean agents) | Not yet in use | Red with a yellow band | A | B | C | E | |||
| Halon | Solid yellow | No longer produced | A | B | E | ||||
| Wet chemical | Solid oatmeal | Red with an oatmeal band | A | F | |||||
United Kingdom
According to the standard BS EN 3, fire extinguishers in the United Kingdom as all throughout Europe are red RAL 3000, and a band or circle of a second color covering between 5–10% of the surface area of the extinguisher indicates the contents. Before 1997, the entire body of the fire extinguisher was color coded according to the type of extinguishing agent.
The UK recognises five fire classes:
- Class A fires involve organic solids such as paper and wood.
- Class B fires involve flammable or combustible liquids, including petrol, grease, and oil.
- Class C fires involve flammable gases.
- Class D fires involve combustible metals.
- Class F fires involve cooking fat and oil.
Class E has been discontinued, but covered fires involving electrical appliances. This is no longer used on the basis that, when the power supply is turned off, an electrical fire can fall into any of the remaining five categories.
| Type | Old code | BS EN 3 colour code | Suitable for use on fire classes (brackets denote sometimes applicable) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Water | Signal red | Signal red | A | ||||||
| Foam | Cream | Red with a cream panel above the operating instructions | A | B | |||||
| Dry powder | French blue | Red with a blue panel above the operating instructions | (A) | B | C | E | |||
| Carbon dioxide CO2 | Black | Red with a black panel above the operating instructions | B | E | |||||
| Wet chemical | Not yet in use | Red with a canary yellow panel above the operating instructions | A | (B) | F | ||||
| Class D powder | French blue | Red with a blue panel above the operating instructions | D | ||||||
| Halon 1211/BCF | Emerald Green | No longer in general use | A | B | E | ||||
In the UK the use of Halon gas is now prohibited except under certain situations such as on aircraft and in the military and police.
Fire extinguishing performance per fire class is displayed using numbers and letters such as 13A, 55B.
EN3 does not recognise a separate electrical class - however there is an additional feature requiring special testing (35 kV dielectric test per EN 3-7:2004). A powder or CO2extinguisher will bear an electrical pictogramme as standard signifying that it can be used on live electrical fires (given the symbol E in the table). If a water-based extinguisher has passed the 35 kV test it will also bear the same electrical pictogramme - however, any water-based extinguisher is only recommended for inadvertent use on electrical fires.
United States
There is no official standard in the United States for the color of fire extinguishers, though they are typically red, except for Class D extinguishers, which are usually yellow, and water, which are usually silver, or white if water mist. Extinguishers are marked with pictograms depicting the types of fires that the extinguisher is approved to fight. In the past, extinguishers were marked with colored geometric symbols, and some extinguishers still use both symbols. The types of fires and additional standards are described in NFPA10: Standard for Portable Fire Extinguishers, 2010 edition.
| Fire Class | Geometric Symbol | Pictogram | Intended Use | Mnemonic | |
|---|---|---|---|---|---|
| A | Green Triangle |  | Ordinary solid combustibles | A for "Ash" | |
| B | Red Square |  | Flammable liquids and gases | B for "Barrel" | |
| C | Blue Circle |  | Energized electrical equipment | C for "Current" | |
| D | Yellow Decagon (Star) |  | Combustible metals | D for "Dynamite" | |
| K | Black Hexagon |  | Oils and fats | K for "Kitchen" |
Fire extinguishing capacity is rated in accordance with ANSI/UL 711: Rating and Fire Testing of Fire Extinguishers. The ratings are described using numbers preceding the class letter, such as 1-A:10-B:C. The number preceding the A multiplied by 1.25 gives the equivalent extinguishing capability in gallons of water. The number preceding the B indicates the size of fire in square feet that an ordinary user should be able to extinguish. There is no additional rating for class C, as it only indicates that the extinguishing agent will not conduct electricity, and an extinguisher will never have a rating of just C.
- For additional US UL rating information see Fast Flow Extinguishers
| American | European | Australian/Asian | Fuel/Heat source |
|---|---|---|---|
| Class A | Class A | Class A | Ordinary combustibles |
| Class B | Class B | Class B | Flammable liquids |
| Class C | Class C | Flammable gases | |
| Class C | UNCLASSIFIED | Class E | Electrical equipment |
| Class D | Class D | Class D | Combustible metals |
| Class K | Class F | Class F | Cooking oil or fat |
Types of Fire Extinguishing Agents
Dry chemical
This is a powder based agent that extinguishes by separating the four parts of the fire tetrahedron. It prevents the chemical reactions involving heat, fuel, and oxygen and halts the production of fire sustaining "free-radicals", thus extinguishing the fire.
- Monoammonium phosphate, also known as "tri-class", "multipurpose" or "ABC" dry chemical, used on class A, B, and C fires. It receives its class A rating from the agent's ability to melt and flow at 177 °C (350 °F) to smother the fire. More corrosive than other dry chemical agents. Pale yellow in color.
- Sodium bicarbonate, "regular" or "ordinary" used on class B and C fires, was the first of the dry chemical agents developed. In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That is, the gas drives oxygen away from the fire, thus stopping the chemical reaction. This agent is not generally effective on class A fires because the agent is expended and the cloud of gas dissipates quickly, and if the fuel is still sufficiently hot, the fire starts up again. While liquid and gas fires don't usually store much heat in their fuel source, solid fires do. Sodium bicarbonate was very common in commercial kitchens before the advent of wet chemical agents, but now is falling out of favor, as it is much less effective than wet chemical agents for class K fires, less effective than Purple-K for class B fires, and is ineffective on class A fires. White or blue in color.
- Potassium bicarbonate (aka Purple-K), used on class B and C fires. About two times as effective on class B fires as sodium bicarbonate, it is the preferred dry chemical agent of the oil and gas industry. The only dry chemical agent certified for use in ARFF by the NFPA. Violet in color.
- Potassium bicarbonate & Urea Complex (aka Monnex/Powerex), used on Class B and C fires. More effective than all other powders due to its ability to decrepitate (where the powder breaks up into smaller particles) in the flame zone creating a larger surface area for free radical inhibition. Grey in color.
- Potassium Chloride, or Super-K dry chemical was developed in an effort to create a high efficiency, protein-foam compatible dry chemical. Developed in the 60s, prior to Purple-K, it was never as popular as other agents since, being a salt, it was quite corrosive. For B and C fires, white in color.
- Foam-Compatible, which is a sodium bicarbonate (BC) based dry chemical, was developed for use with protein foams for fighting class B fires. Most dry chemicals contain metal stearates to waterproof them, but these will tend to destroy the foam blanket created by protein (animal) based foams. Foam compatible type uses silicone as a waterproofing agent, which does not harm foam. Effectiveness is identical to regular dry chemical, and it is light green in color (some ANSUL brand formulations are blue). This agent is generally no longer used since most modern dry chemicals are considered compatible with synthetic foams such as AFFF.
- MET-L-KYL / PYROKYL is a specialty variation of sodium bicarbonate for fighting pyrophoric liquid fires (ignite on contact with air). In addition to sodium bicarbonate, it also contains silica gel particles. The sodium bicarbonate interrupts the chain reaction of the fuel and the silica soaks up any unburned fuel, preventing contact with air. It is effective on other class B fuels as well. Blue/Red in color.
Foams
Applied to fuel fires as either an aspirated (mixed & expanded with air in a branch pipe) or nonaspirated form to form a frothy blanket or seal over the fuel, preventing oxygen reaching it. Unlike powder, foam can be used to progressively extinguish fires without flashback.
- AFFF (aqueous film forming foam), used on A and B fires and for vapor suppression. The most common type in portable foam extinguishers. It contains fluoro tensides which can be accumulated in the human body. The long-term effects of this on the human body and environment are unclear at this time.
- AR-AFFF (Alcohol-resistant aqueous film forming foams), used on fuel fires containing alcohol. Forms a membrane between the fuel and the foam preventing the alcohol from breaking down the foam blanket.
- FFFP (film forming fluoroprotein) contains naturally occurring proteins from animal by-products and synthetic film-forming agents to create a foam blanket that is more heat resistant than the strictly synthetic AFFF foams. FFFP works well on alcohol-based liquids and is used widely in motorsports.
- CAFS (compressed air foam system) Any APW style extinguisher that is charged with a foam solution and pressurized with compressed air. Generally used to extend a water supply in wildland operations. Used on class A fires and with very dry foam on class B for vapor suppression.
- Arctic Fire is a liquid fire extinguishing agent that emulsifies and cools heated materials more quickly than water or ordinary foam. It is used extensively in the steel industry. Effective on classes A, B, and D.
- FireAde, a foaming agent that emulsifies burning liquids and renders them non-flammable. It is able to cool heated material and surfaces similar to CAFS. Used on A and B (said to be effective on some class D hazards, although not recommended due to the fact that fireade still contains amounts of water which will react with some metal fires).
Cools burning material.
- APW (Air pressurized water) cools burning material by absorbing heat from burning material. Effective on Class A fires, it has the advantage of being inexpensive, harmless, and relatively easy to clean up. In the United States, APW units contain 2.5 gallons (9 liters) of water in a tall, stainless steel cylinder. In Europe, they are typically mild steel lined with polyethylene, painted red, containing 6–9 liters (1.75–2.5 gallons) of water.
- Water Mist uses a fine misting nozzle to break up a stream of deionized water to the point of not conducting electricity back to the operator. Class A and C rated. It is used widely in hospitals for the reason that, unlike other clean-agent suppressants, it is harmless and non-contaminant. These extinguishers come in 1.75 and 2.5 gallon units, painted white in the United States and red in Europe.
Wet chemical and water additives
- Wet Chemical (potassium acetate, carbonate, or citrate) extinguishes the fire by forming a soapy foam blanket over the burning oil and by cooling the oil below its ignition temperature. Generally class A and K (F in Europe) only, although newer models are outfitted with misting nozzles as those used on water mist units to give these extinguishers class B and C firefighting capability.
- Wetting Agents Detergent based additives used to break the surface tension of water and improve penetration of Class A fires.
- Antifreeze Chemicals added to water to lower its freezing point to about −40 °F. Has no appreciable effect on extinguishing performance.
Clean agents and carbon dioxide
Agent displaces oxygen (CO2 or inert gases), removes heat from the combustion zone (Halotron, FE-36) or inhibits chemical chain reaction (Halons). They are labelled clean agents because they do not leave any residue after discharge which is ideal for sensitive electronics and documents.
- Halon (including Halon 1211 and Halon 1301), a gaseous agent that inhibits the chemical reaction of the fire. Classes B:C for lower weight fire extinguishers (2.3 kg; under 9 lbs) and A:B:C for heavier weights (4.1–7.7 kg; 9–17 lbs). Banned from new production, except for military use, as of January 1, 1994 as its properties contribute to ozone depletion and long atmospheric lifetime, usually 400 years. Halon was completely banned in Europe resulting in stockpiles being sent to the United States for reuse. Although production has been banned, the reuse is still permitted. Halon 1301 and 1211 are being replaced with new halocarbon agents which have no ozone depletion properties and low atmospheric lifetimes, but are less effective.
- Halocarbon replacements, HCFC Blend B (Halotron I, American Pacific Corporation), HFC-227ea (FM-200, Great Lakes Chemicals Corporation), and HFC-236fa (FE-36, DuPont), have been approved by the FAA for use in aircraft cabins in 2010. Considerations for halon replacement include human toxicity when used in confined spaces, ozone depleting potential, and greenhouse warming potential. The three recommended agents meet minimum performance standards, but uptake has been slow because of disadvantages. Specifically, they require two to three times the concentration to extinguish a fire compared with Halon 1211. They are heavier than halon, require a larger bottle because they are less effective, and have greenhouse gas potential. Research continues to find better alternatives.
- CO2, a clean gaseous agent which displaces oxygen. Highest rating for 7.7 kg (20 pound) portable CO2 extinguishers is 10B:C. Not intended for Class A fires, as the high-pressure cloud of gas can scatter burning materials. CO2 is not suitable for use on fires containing their own oxygen source, metals or cooking media. Although it can be rather successful on a person on fire, its use should be avoided where possible as it can cause frostbite and is dangerous to use as it may displace the oxygen needed for breathing, causing suffocation.
- Mixtures of inert gases, including Inergen and Argonite.
- compressed CO2 sprinkler is another design used to fight the electric fires with cubic cylinder of 7 cubic meter starting from 1 meter above the sprinkler level.
- Novec 1230 fluid (aka "dry water" or Saffire fluid), a fluoronated ketone that works by removing massive amounts of heat. Available in fixed systems in the US and in portables in Australia. Unlike other clean agents, this one has the advantage of being a liquid at atmospheric pressure, and can be discharged as a stream or a rapidly vaporizing mist, depending on application.
- Potassium Aerosol Particle Generator, contains a form of solid potassium and other chemicals referred to as Aerosol Forming Compounds (AFC). The AFC is activated by an electrical current or other thermodynamic exchange which causes the AFC to ignite. The Majority of installed currently are fixed units due to the possibility of harm to the user from the heat generated by the AFC generator.
Class D
There are several Class D fire extinguisher agents available; some will handle multiple types of metals, others will not.
- Sodium Chloride (Super-D, Met-L-X or METAL.FIRE.XTNGSHR) contains sodium chloride salt, which melts to form an oxygen-excluding crust over the metal. Useful on most alkali metals including sodium and potassium, and other metals includingmagnesium, titanium, aluminum, and zirconium.
- Copper based (Copper Powder Navy125S) developed by the U.S. Navy in the 70s for hard-to-control lithium and lithium-alloy fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface-lithium only.
- Graphite based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR) contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well. Unlike sodium chloride powder extinguishers, the graphite powder fire extinguishers can be used on very hot burning metal fires such as lithium, but unlike copper powder extinguishers will not stick to and extinguish flowing or vertical lithium fires. Like copper extinguishers, the graphite powder acts as a heat sink as well as smothering the metal fire.
- Sodium carbonate based (Na-X) used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. Limited use on other metals. Smothers and forms a crust.
- Some water based suppressants may be used on certain class D fires, such as burning titanium and magnesium. Examples include the Fire Blockade and FireAde brands of suppressant. Some metals, such as elemental Lithium, will react explosively with water, therefore water-based chemicals should never be used on such fires due to the possibility of a violent reaction.
Most Class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel.
Fire extinguishing ball
Several modern ball or "grenade" style extinguishers are on the market. They are manually operated by rolling or throwing into a fire. The modern version of the ball will self-destruct once in contact with flame, dispersing a cloud of ABC dry chemical powder over the fire which extinguishes the flame. The coverage area is about 5 square meters. One benefit of this type is that it may be used for passive suppression. The ball can be placed in a fire prone area and will deploy automatically if a fire develops, being triggered by heat. Most modern extinguishers of this type are designed to make a loud noise upon deployment.
This technology is not new, however. In the 1800s, glass fire grenades filled with suppressant liquids were popular. These glass fire grenade bottles are sought by collectors. Some later brands, such as Red Comet, were designed for passive operation, and included a special holder with a spring-loaded trigger that would break the glass ball when a fusible link melted. As was typical of this era, some glass extinguishers contained the toxic carbon tetrachloride.
Condensed aerosol fire suppression
Condensed aerosol fire suppression is a particle-based form of fire extinction similar to gaseous fire suppression or dry chemical fire extinction. As with gaseous fire suppressants, condensed aerosol suppressants use clean agents to suppress the fire. The agent can be delivered by means of mechanical operation, electric operation, or combined electro-mechanical operation. To the difference of gaseous suppressants, which emit only gas, and dry chemical extinguishers, which release powder-like particles of a large size (25-150 microns) condensed aerosols are defined by the National Fire Protection Association as releasing finely-divided solid particles (generally <10 microns), usually in addition to gas.
Whereas dry chemical systems must be directly aimed at the flame, condensed aerosols are flooding agents and therefore effective regardless of the location and height of the fire. Wet chemical systems, such as the kind generally found in foam extinguishers, must, similarly to dry chemical systems, be sprayed directionally, onto the fire. Additionally, wet chemicals (such as potassium carbonate) are dissolved in water, whereas the agents used in condensed aerosols are microscopic solids.
Selecting Appropriate PPE
Workplace Fire Fighting Team must be provided with approriate fire clothings :
1. Breathing apparatus (SCBA)
2. Fire proof clothing
3. Fire proof boots
4. Heat resistant helmets
5. Heat resistant mask
6. Heat resistant gloves
7. Chemical splash clothing (when necessary)
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Fire Fighting Procedure
1. Identify the chemical hazard before fighting the fire.
2. Refer to the MSDS for correct fire fighting procedure.
3. Observe the chemical reaction information
(during fire, in contact with other material i.e. water, and after fire)
4. Wear approriate PPE.
5. Fight fire using recommended extinguishing agent and method :
a) Starvation method
- Reducing or removing the fuel from the scene of the fire.
b) Smothering method
- Reducing or cutting off the oxygen supply from the scene of fire.
c) Cooling method
- Lowering the temperature or reducing the heat.
There are several methods firefighters use to put out fires. Fire needs 3 things to survive, called "the triangle of fire", heat, oxygen, and fuel. All firefighting techniques remove one of those elements to put out the fire. The first is to spray water or fire retardant on the fire, either using a fire hose or a special aircraft. They smother the fire, removing oxygen, and water cools it. Another method is a fire break. A fire break is a space with no fuel. Therefore, the fire cannot burn past the fire break, and the fire eventually exhausts its fuel and burns out. Those are the two most common ways to put out a fire.
Recent thinking on fires treat them as a four legged stool, now including "chain reaction." Some newer firefighting methods simply break the chain reaction to stop the fire. Chemicals are often used on fires, but the best know way is to use a fine spray of water. Although the water cools the fire (and resulting steam remove oxygen), a spray or even foam can separate the fuel from the air, starving the fire as it rapidly cools.