Fire extinguisher
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A fire extinguisher

A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not designed 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 handheld cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire.

Types of Extinguishers

There are two main types of fire extinguishers: Stored pressure and generated pressure. In stored pressure units, the expellant is stored in the same chamber as the firefighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers, nitrogen is typically used; water and foam are pressurized with air. Stored pressure are the most common type fire extinguishers. Generated pressure, or cartridge-operated extinguishers, contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the agent. These types as are not 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 an reasonable amount of time. Unlike stored pressure types, these extinguishers utilize compressed carbon dioxide instead of nitrogen.

Fire extinguishers are further divided into handheld and cart-mounted, also called wheeled extinguishers. Handheld extinguishers weight from 2 to 30 pounds (1 to 14 kilograms), and are hence easily portable by hand. They exist in both stored- and generated-pressure types and contain all types of suppressants. Cart-mounted units typically weigh 50+ pounds (23+ kilograms), are cartridge-operated, and typically contain either dry chemical, Purple-K, foam, Halon, or CO₂. Wheeled models are most commonly found at construction sites, airport runways, heliports, and temporary landing sites.

History

A 1905 illustration marketing extinguishers.

The first automatic fire extinguisher of which there is any record was patented in England in 1723 by Ambrose Godfrey, a celebrated chemist. It consisted of a cask of fire-extinguishing liquid containing a pewter chamber of gunpowder. This was connected with a system of fuses which were ignited, exploding the gunpowder and scattering the solution. This device was probably used to a limited extent, as Bradley's Weekly Messenger for November 7, 1729, refers to its efficiency in stopping a fire in London.

The modern fire extinguisher was invented by British Captain George William Manby in 1818; it consisted of a copper vessel of 3 gallons (13.6 litres) of pearl ash (potassium carbonate) solution contained within compressed air.

The soda-acid extinguisher was invented in 1881 by Almon M. Granger. His extinguisher used the reaction between sodium bicarbonate solution and sulfuric acid to expel pressurized water onto a fire.^[1]

A vial was suspended in the cylinder containing concentrated sulfuric acid. Depending on the type of extinguisher, the vial of acid could be broken in one of two ways. One used a plunger to break the acid vial, while the second released a lead bung that held the vial closed. Once the acid was mixed with the bicarbonate solution, carbon dioxide gas was expelled and thereby pressurize the water. The pressurized water was forced from the canister through a nozzle or short length of hose.

Around 1912 Pyrene invented the carbon tetrachloride (CTC) extinguisher, which expelled the liquid from a brass or chrome container by a handpump; it was usually of 1 imperial quart (1.1 L) or 1 imperial pint (0.6 L) capacity but was also available in up to 2 imperial gallon (9 L) size. A further variety consisted of a glass bottle "bomb" filled with the liquid that was intended to be hurled at the base of a fire. The CTC vaporized and extinguished the flames by chemical reaction. The extinguisher was suitable for liquid and electrical fires, and was popular in motor vehicles for the next 60 years. In the 1940s, Germany invented the liquid chlorobromomethane (CBM) for use in aircraft. It was more effective and slightly less toxic than carbon tetrachloride and was used until 1969. Methyl Bromide was discovered as an extinguishing agent in the 1920s and was used extensively in Europe. It is a low-pressure gas that works by inhibiting the chain reaction of the fire and is the most toxic of the vaporizing liquids, used until the 1960s. The vapor and combustion by-products of all vaporizing liquids were highly toxic, and could cause death in confined spaces.

Classification

Internationally there are several accepted classification methods for hand-held fire extinguishers. Each classification is useful in fighting fires with a particular group of fuel.

Australia

In Australia, yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted.^[2]

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 at least 5% 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.

Typical United Kingdom CO2 and water fire extinguishers

The UK recognizes six fire classes. Class A fires involve organic solids such as paper and wood. Class B fires involve flammable liquids. Class C fires involve flammable gases. Class D fires involve metals, Class E fires involve live electrical items and Class F fires involve cooking fat and oil. Fire extinguishing capacity is rated by fire class using numbers and letters such as 13A, 55B. EN 3 does not recognize a separate E class - this is an additional feature requiring special testing (dielectric test per EN 3-7:2004) and NOT passing this test makes it compulsory to add a special label (pictogram) indicating the inability to isolate the user from a live electric source.

In the UK the use of Halon gas is now illegal except under certain situations.^[3]

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 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. No official pictogram exists for Class D extinguishers, though training manuals sometimes show a drill press with shavings burning underneath. The types of fires and additional standards are described in NFPA 10: Standard for Portable Fire Extinguishers.

The Underwriters Laboratories rate fire extinguishing capacity in accordance with UL/ANSI 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

Installation

Fire extinguishers are typically fitted in buildings at an easily-accessible location, such as against a wall in a high-traffic area. They are also often fitted to motor vehicles, watercraft, and aircraft - this is required by law in many jurisdictions, for identified classes of vehicles. Under NFPA 10 all commercial vehicles must carry at least one fire extinguisher (size/UL rating depending on type of vehicle and cargo (ie. fuel tankers typically must have a 9.1 kg (20 lb). when most others can carry a 2.3 kg (5 lb).) The revised NFPA 10 created criteria on the placement of "Fast Flow Extinguishers" in locations such as those storing and transporting pressurized flammable liquids and pressurized flammable gas or areas with possibility of three dimensional class B hazards are required to have "fast flow" extinguishers as required by NFPA 5.5.1.1.

A fire extinguisher fitted to the passenger seat of a car.

Varying classes of competition vehicles require fire extinguishing systems, the simplest requirements being a 1A10BC handheld portable extinguisher mounted to the interior of the vehicle.

Types of extinguishing agents

Dry Chemical (lyophobic colloid)

A small, disposable sodium bicarbonate dry chemical unit intended for home kitchen use.

A typical dry chemical extinguisher: 5lbs. monoammonium phosphate dry chemical.

Powder based agent that extinguishes by separating the four parts of the fire tetrahedron. It prevents the chemical reaction between heat, fuel and oxygen, thus extinguishing the fire.

• Monoammonium phosphate, also known as ABC Dry Chemical, used on class A, B, and C fires. It receives its class A rating from the agents ability to melt and flow at 177 °C (350 °F) to smother the fire. More corrosive than other dry chemical agents.
• Sodium bicarbonate, used on class B and C fires. Interrupts the fire's chemical reaction.
• Potassium bicarbonate (aka Purple-K), used on class B and C fires. About two times as effective on class B fires as sodium bicarbonate. The preferred dry chemical agent of the oil and gas industry. The only dry chemical agent certified for use in AR-FF by the NFPA.
• Potassium bicarbonate & Urea Complex (aka Monnex), 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.

Foams (lyophilic colloid)

Applied to fuel fires as either an aspirated (mixed & expanded with air in a branch pipe) or non aspirated 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 extinguishers. It contains flour tensides ^[4] which can be accumulated in human body.
• 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 fats to create a foam blanket that is more heat resistant then the synthetic AFFF foams.

An American water extinguisher

Water

Cools burning material.

• APW (Air pressurized water) cools burning material by absorbing heat from burning material. Effective on only Class A fires, but has the advantage of being inexpensive, harmless, and relatively easy to clean up.
• 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. Used widely in hospitals for the reason that unlike other clean-agent suppressants, it is harmless and non-contaminant.

Water Additives

• Wet Chemical (potassium acetate) extinguishes the fire by forming a soapy foam blanket over the burning oil (saponification) and by cooling the oil below its ignition temperature. Generally class A and K (F in Europe) only.
• Wetting Agents Detergent based additives used to break the surface tension of water and improve penetration of Class A fires. Enables a 3 liter water extinguisher to achieve the fire fighting capacity of a 9 liter plain water type.

Clean Agents

Agent does not extinguish by smothering, but displaces oxygen, or inhibits chemical chain reaction. They are labeled 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 ; 5 lbs or less) 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 halons which have no ozone depletion properties and low atmospheric lifetimes, but are less effective. Currently Halotron I and Halotron II are meant to be replacements with significantly reduced ozone depletion potential.
• 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.
• Mixtures of inert gases, including Inergen and Argonite.

Class D

• Sodium chloride/Bicarbonate Urea Graphite and Copper forms a crust over the burning metal and performs like a heat sink to draw heat away from the burning material, also smothers to a degree. Copper dry powder was developed by the U.S. Navy for lithium fires and will cling to vertical surfaces.

Maintenance

An empty fire extinguisher which was not replaced for years.

Most countries in the world require regular fire extinguisher maintenance by a competent person to operate safely and effectively, as part of fire safety legislation. Lack of maintenance can lead to an extinguisher not discharging when required, or rupturing when pressurized. Deaths have occurred, even in recent times, from corroded extinguishers exploding.

There is no all-encompassing fire code in the United States. Generally, most municipalities (by adoption of the International Fire Code) require inspections every 30 days to ensure the unit is pressurized and unobstructed (done by an employee of the facility) and an annual inspection by a qualified technician. Hydrostatic pressure testing for all types of extinguishers is also required, generally every five years for water and CO₂ models up to every 12 years for dry chemical models.

Recently the National Fire Protection Association and ICC voted to allow for the elimination of the 30 day inspection requirement so long as the fire extinguisher is monitored electronically. According to NFPA, the system must provide record keeping in the form of an electronic event log at the control panel. The system must also constantly monitor an extinguisher’s physical presence, internal pressure and whether an obstruction exists that could prevent ready access. In the event that any of the above conditions are found, the system must send an alert to officials so they can immediately rectify the situation. Electronic monitoring can be wired or wireless.

In the UK, three types of maintenance are required:

• Basic Service: All types of extinguisher require a basic inspection annually to check weight, correct pressure (using a special tool, not just looking at the gauge) and for signs of damage or corrosion, cartridge extinguishers are opened up for internal inspection & check weighing of the cartridge, labels are checked for legibility, where possible dip tubes, hoses and mechanisms checked for clear free operation.

• Extended Service: Water, Wet Chemical, Foam & Powder extinguishers require every five years a more detailed examination including a test discharge of the extinguisher and recharging- on stored pressure extinguishers this is the only opportunity to internally inspect for damage/corrosion. By recharging fresh agent is used as they all have a shelf life, even water goes foul inside an extinguisher; Note: extinguishers should be percentage tested according to total number of units in any given area. Some extinguishers contain pressure in excess of 1.38 MPa (200psi) and this internal pressure over periods of time affects each brand & make differently depending on their placement & location.

• Overhaul: CO₂ extinguishers, due to their high operating pressure, are subject to pressure vessel safety legislation and must be hydraulic pressure tested, inspected internally & externally and date stamped every 10 years (Every 5 years in the U.S.). As it cannot be pressure tested a new valve is also fitted. If replacing any part of the extinguisher (valve, horn etc) with a part from another manufacturer then the extinguisher will lose its fire rating. This may invalidate insurance, as would incorrect or inadequate servicing if it were to be found.

Fire extinguisher signs

Heavy-duty CO₂-powered fire extinguisher on standby at a temporary helicopter landing site

Fire extinguisher identification signs are small signs designed to be mounted near a fire extinguisher, in order to draw attention to the extinguisher's location (Ex. If the Extinguisher is on a large pole the sign would generally be at the top of the pole so it can be seen from a distance) Such signs may be manufactured from a variety of materials, commonly self-adhesive vinyl, rigid PVC and aluminum.

In addition to words and pictographs indicating the presence of a fire extinguisher , modern extinguisher ID signs also describe the extinguishing agent in the unit, and summarize the types of fire on which it may safely be used.

Public and government buildings are often required, by local legal codes, to provide an ID sign for each extinguisher on the site.^[5]

Similar signs are available for other fire equipment (including fire blankets and fire hose reels), and for other emergency equipment (such as first aid kits).

Placement of fire extinguisher signs

Fire extinguisher signs are mounted above or to the side of the extinguisher they relate to.

Most licensing authorities have regulations describing the standard appearance of these signs (e.g. text height, pictographs used and so on)^[6].

Photo-luminescent fire extinguisher signs

Photo-luminescent fire extinguisher signs are made of a polymer that absorbs ambient light and releases it slowly in dark conditions - the sign "glows in the dark". Such signs are independent of an external power supply, and so offer a low-cost, reliable means of indicating the position of emergency equipment in dark or smoky conditions.

Photo-luminescent signs are sometimes mis-described as being reflective. A reflective material will only return ambient light for as long as the light source is supplied, rather than storing energy and releasing it over a period of time. However, many fire extinguishers and extinguisher mounting posts have strips of reflective adhesive tape placed on them to facilitate their location in situations where only emergency lighting or flashlights are available.

Older luminescent signs sometimes used a radioactive tritium source to energise the polymeric material. This source could pose a hazard when such signs are dismantled or damaged^[7]. Modern photoluminescent materials are, however, not radioactive.

References

Automatic Sprinkler Protection - Goram Dana, S.B.

External links

Wikimedia Commons has media related to:

Fire extinguisher

• Underwriters Laboratories tips
• MSDS Sheets for hand held portable fire extinguishers
• OSHA requirements
• -Extinguisher-museum.com > Online museum about antique fire extinguishers and their history
• Fire Extinguisher Advice
• Fire Extinguisher Information Site
• National Fire Help
• How to use a fire extinguisher
• Aviation requirements for fire extinguishers

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General: Active fire protection — Fire alarm system Fire suppression: Fire extinguisher — Fire sand bucket — Fire sprinkler — Gaseous fire suppression Detection/alarm: Control panel — Heat detector — Pull station — Fire alarm box — Notification appliance — Smoke detector Practices: Fire drill — Fire drill regulations in the USA