Firefighting Foams

Foams for firefighting appHcations are typically made from a concentrated foaming agent diluted with water and then mixed with air. Rather than consider the volume fraction of air in the foam, firefighting foams are characterized by their expansion ratio, which is the increase in volume of the Hquid after the foam is formed. Expansion ratios range from 5 1 to over 1000 1 ratios of 5 1 to 20 1 are called low expansion ratios of 21 1 to 200 1, medium expansion and ratios greater than 200 1, high expansion. 

Supplies of foam firefighting agents can be stored in portable trailers and totes taken to the site where they will be used. Trailers come in a variety of sizes. Smaller wheeled carts can be pushed by employees, while others need to be transported by a vehicle. 

Observe normal precautions appropriate to the circumstances and quantity of material handled. Chitosan is combustible open flames should be avoided. Chitosan is temperature-sensitive and should not be heated above 200°C. Airborne chitosan dust may explode in the presence of a source of ignition, depending on its moisture content and particle size. Water, dry chemicals, carbon dioxide, sand, or foam firefighting media should be used. 

Formaldehyde constitntes about 50% of all aldehydes present in the air. It is one of the toxic efUnent gases emitted from burning wood and synthetic polymeric substances such as polyethylene, nylon 6, and polyurethane foams. Firefighters have a greater risk to its exposure. Incapacitation from the toxic effluent gases is reported to occur more rapidly from the combustion of synthetic polymers than from that of natural cellulose materials. 

Flammable liquid flash point (closed cup) -11°C (12°F) vapor pressure 160 torr at 20°C (68°F) vapor density 1.48 (air = 1) the vapor is heavier than air and can travel a considerable distance to a source of ignition and flash back autoignition temperature 322°C (612°F) fire-extinguishing agent dry chemical or alcohol foam firefighting should be done from an explosion-resistant area use water to flush and dilute any spill and to keep Are-exposed containers cool. Ethylenimine may polymerize under fire conditions. The reaction is exothermic, which may cause violent rupture of the container. 

Deceth-4 Deceth-6 Deceth-9 penetrant, foams firefighting Ammonium hexyl sulfate penetrant, food... 

Flammability Acrolein is very flammable its flash point is <0° C, but a toxic vapor cloud will develop before a flammable one. The flammable limits in air are 2.8% and 31.0% lower and upper explosive limits, respectively by volume. Acrolein is only partly soluble in water and will cause a floating fire, so alcohol type foam should be used in firefighting. The vapors are heavier than air and can travel along the ground and flash back from an ignition source. 

Ammonium and alkanolamine salts of alcohol C12-C14 sulfates are used as foamers in the formulation of firefighting foams. 

Moody CA, JA Field (2000) Perfinorinated snrfactants and environmental implications of their nse in firefighting foams. Environ Sci Technol 34 3864-3870. 

Properly applied firefighting foam can be an effective fire suppressant for most flammable or combustible liquids stored in vertical cylindrical tanks. Foam may... 

In general, fixed water spray fire protection has the two-fold purpose of cooling the affected equipment and flushing any burning liquids from the immediate fire area. This can reduce local damage, limit fire spread, and allow time for other response actions. It should not be expected that these systems will extinguish a fire without the use of other fire protection systems, such as foam, dry chemical, or manual firefighting. 

Manual firefighting, using both water and foam application... 

Firefighting foam is the extinguishing agent typically utilized for flammable and combustible liquid storage tank protection. Protection is through fixed and manual systems for tanks. Such systems require ... 

Where water supplies are inadequate for conventional firefighting and foam making, automatically activated fixed clean agent or CO2 systems may be considered for seal fire protection. The agent should be discharged into the seal area below the secondary seal. Fire detection options for these automatic systems include reusable thermal wires and pneumatic tube devices. Thermal wire is typically the more economical choice. 

Rain drops Combustion engines Soap bubbles Foam (in firefighting)... 

The U.S. Air Force tested the effectiveness of ASH at treating emulsified oil, fuel, and grease, as well as aqueous, fihn-forming foam (AFFF) liquids. These contaminants are common in aircraft wash-rack wastewater and firefighting wastewater. Based on test results, the Air Force determined that ASH can treat contaminated wastewater at a cost of 0.40 to 1.10 per 1000 gal (D208219, p. 502). 

Another phenomenon associated with a crude oil fire is stopover. Basically, die same principles that are responsible for a boilover are the cause of a stopover. The fundamental difference is that in a stopover the reaction is from water that has entered the tank since the start of the fire. Usually this introduction is die result of firefighting activities. A slopover will occur at some point after the heat wave lias been formed. Eidier the water from the hose streams or, after the bubbles collapse, the water in the foam will sink into the oil, contacting the heat wave, where it is converted to steam, and die agitation of the liquid surface spills some amount of oil over the tank rim. 

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