Automatic fire suppression

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Automatic system in a computer room

Automatic fire suppression systems control and extinguish fires without human intervention. Examples of automatic systems include fire sprinkler system, gaseous fire suppression, and condensed aerosol fire suppression.

The first fire extinguisher patent was issued to Alanson Crane of Virginia on Feb. 10, 1863. The first fire sprinkler system was patented by H.W. Pratt in 1872. But the first practical automatic sprinkler system was invented in 1874 by Henry S. Parmalee of New Haven, CT. He installed the system in a piano factory he owned.

Types of automatic systems[edit]

Today there are numerous types of Automatic Fire Suppression Systems. Systems are as diverse as the many applications. In general, however, Automatic Fire Suppression Systems fall into two categories: engineered and pre-engineered systems.

Engineered Fire Suppression Systems are design specific. Engineered systems are usually for larger installations where the system is designed for the particular application. Examples include marine and land vehicle applications, computer clean rooms, public and private buildings, industrial paint lines, dip tanks and electrical switch rooms. Engineered systems use a number of gaseous or solid agents. Many are specifically formulated. Some, such as 3M Novec 1230 Fire Protection Fluid, are stored as a liquid and discharged as a gas.

Pre-Engineered Fire Suppression Systems use pre-designed elements to eliminate the need for engineering work beyond the original product design. Typical industrial solutions use a simple wet or dry chemical agent, such as potassium carbonate or monoammonium phosphate (MAP), to protect spaces such as paint rooms and booths, storage areas and commercial kitchens. In Europe, a small number of residential designs have also emerged. These units often employ water mist with or without a surfactant additive, and target retrofit applications where the risk of fire or fire injury is high but where a conventional fire sprinkler system would be unacceptably expensive.

Components[edit]

By definition, an automatic fire suppression system can operate without human intervention. To do so it must possess a means of detection, actuation and delivery.

In many systems, detection is accomplished by mechanical or electrical means. Mechanical detection uses fusible-link or thermo-bulb detectors. These detectors are designed to separate at a specific temperature and release tension on a release mechanism. Electrical detection uses heat detectors equipped with self-restoring, normally-open contacts which close when a predetermined temperature is reached. Remote and local manual operation is also possible.

Actuation usually involves either a pressurised fluid and a release valve, or in some cases an electric pump.

Delivery is accomplished by means of piping and nozzles. Nozzle design is specific to the agent used and coverage desired.

Extinguishing agents[edit]

In the early days, water was the exclusive fire suppression agent. Although still used today, water has limitations. Most notably, its liquid and conductive properties can cause as much property damage as fire itself.

Agent Primary Ingredient Applications
FM-200 Heptafluoropropane Electronics, medical equipment, production equipment, libraries, data centers, medical record rooms, server rooms, oil pumping stations, engine compartments, telecommunications rooms, switch rooms, engine and machinery spaces, pump rooms, control rooms
3M Novec 1230 Fire Protection Fluid Fluorinated Ketone Electronics, medical equipment, production equipment, libraries, data centers, medical record rooms, server rooms, oil pumping stations, engine compartments, telecommunications rooms, switch rooms, engine and machinery spaces, pump rooms, control rooms
IG-55 Argon and nitrogen Same applications and FM-200 and Novec 1230 fluid; less Class B style hazards
FE-13 Fluoroform Police evidence freezers, inerting natural gas pumping stations or trains/trucks/cranes operating in cold weather, electronics, medical equipment, production equipment, libraries, data centers, medical record rooms, server rooms, oil pumping stations, engine compartments, telecommunications rooms, switch rooms, engine and machinery spaces, pump rooms, control rooms
Wet Chemical Potassium carbonate Commercial kitchens
ABC Dry Chemical Monoammonium phosphate Paint booths, dip tanks, coating operations, flammable liquid storage areas, paint mixing areas, exhaust ducts
Regular Dry Chemical Sodium bicarbonate Gasoline, propane and solvents, live electrical equipment, flammable liquids
Carbon Dioxide Carbon Dioxide Non-occupied control rooms, coating operations, paint lines, dust collectors, transformer vaults, live electrical equipment, flammable liquids, commercial fryers
Foam Synthetic detergent, polysaccharide, fluoroakyl suffaccant Flammable liquids
Purple K Dry Chemical Potassium bicarbonate High hazard commercial and industrial applications, especially with flammable liquids
Solid aerosol particulate Potassium nitrate Used in condensed aerosol fire suppression, high hazard commercial and industrial applications, no ozone depletion or global warming potential
Halotron 1 2,2-dichloro-1,1,1-trifluoroethane Live electrical equipment, flammable liquids
Water Mist Water All Classes of Fire (A,B,C,F) Ordinary flammables (Paper, wood, cloth), Flammable liquids, Kitchen Fires (K,F Class), Electrical Fires
Water Water Ordinary flammables (Paper, wood, cloth)

Health and environmental concerns[edit]

Despite their effectiveness, chemical fire extinguishing agents are not without disadvantages. In the early 20th century, carbon tetrachloride was extensively used as a dry cleaning solvent, a refrigerant and as a fire extinguishing agent. In time, it was found carbon tetrachloride could lead to severe health effects.

From the mid-1960s Halon 1301 was the industry standard for protecting high value assets from the threat of fire. Halon 1301 had many benefits as a fire suppression agent; it is fast acting, safe for assets and required minimal storage space. Halon 1301s major drawbacks are that it depletes atmospheric ozone and is potentially harmful to humans.

Since 1987, some 191 nations have signed The Montreal Protocol on Substances That Deplete the Ozone Layer. The Protocol is an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. Among these were halogenated hydrocarbons often used in fire suppression. As a result manufacturers have focused on alternatives to Halon 1301 and Halon 1211 (halogenated hydrocarbons).

A number of countries have also taken steps to mandate the removal of installed Halon systems. Most notably these include Germany and Australia, the first two countries in the world to require this action. In both of these countries complete removal of installed Halon systems has been completed except for a very few essential use applications. The European Union is currently undergoing a similar mandated removal of installed Halon systems.

Modern systems[edit]

Since the early 1990s manufacturers have successfully developed safe and effective Halon alternatives. These include DuPont FM-200, American Pacific’s Halotron and 3M Novec 1230 Fire Protection Fluid. Generally, the Halon replacement agents available today fall into two broad categories, in-kind (gaseous extinguishing agents) or not in-kind (alternative technologies). In-kind gaseous agents generally fall into two further categories, Halocarbons and Inert Gases. Not in-kind alternatives include such options as water mist or the use of early warning smoke detection systems.

References[edit]