Extinguishing Agents and Portable Fire  Extinguishers Inert Cold Gases Halogenated Hydrocarbons Dry Powders Water 17-10 Figure 17-10.  Hand held fire extinguisher requirement for transport  aircraft. Class A type fires are best controlled with water by cooling  the material below its ignition temperature and soaking the  material to prevent re-ignition. Class A, B, or C fires can be controlled by dry chemical  extinguishing agents. The only all purpose (Class A, B, C  rating) dry chemical powder extinguishers contain mono- ammonium phosphate. All other dry chemical powders  have a Class B, C U.S – UL fire rating only. Dry powder  chemical extinguishers best control class A, B, and C fire  but their use is limited due to residual residue and clean up  after deployment. NOTE: While Halons are still in service and are appropriate  agents for these classes of fires, the production of these  Two types of Halons are employed in aviation: Halon  1301(CBrF$_{3}$) a total flooding agent, and Halon 1211  (CBrClF$_{2}$) a streaming agent. Class A, B, or C fires are  appropriately controlled with Halons. However, do not use  Halons on a class D fire. Halon agents may react vigorously  with the burning metal.  For over 45 years, halogenated hydrocarbons (Halons) have  been practically the only fire extinguishing agents used in civil  transport aircraft. However, Halon is an ozone depleting and  global warming chemical, and its production has been banned  by international agreement. Although Halon usage has been  banned in some parts of the world, aviation has been granted  an exemption because of its unique operational and fire safety  requirements. Halon has been the fire extinguishing agent  of choice in civil aviation because it is extremely effective  on a per unit weight basis over a wide range of aircraft  environmental conditions. It is a clean agent (no residue),  electrically nonconducting, and has relatively low toxicity.  There must be at least one hand held, portable fire  extinguisher for use in the pilot compartment that is located  within easy access of the pilot while seated. There must be at  least one hand held fire extinguisher located conveniently in  the passenger compartment of each airplane accommodating  more than 6 and less than 30 passengers. Each extinguisher  for use in a personnel compartment must be designed to  minimize the hazard of toxic gas concentrations. The number  of portable, hand held fire extinguishers for transport aircraft  is shown in  Figure 17-10. ozone depleting agents has been restricted. Although not  required, consider replacing Halon extinguishers with  Halon replacement extinguishers when discharged. Halon  replacement agents found to be compliant to date include the  halocarbons HCFC Blend B, HFC-227ea, and HFC-236fa. Carbon dioxide (CO$_{2}$) is an effective extinguishing agent. It  is most often used in fire extinguishers that are available on  the ramp to fight fires on the exterior of the aircraft, such as  engine or APU fires. CO$_{2}$ has been used for many years to  extinguish flammable fluid fires and fires involving electrical  equipment. It is noncombustible and does not react with most  substances. It provides its own pressure for discharge from  the storage vessel, except in extremely cold climates where  a booster charge of nitrogen may be added to winterize the  system. Normally, CO$_{2}$ is a gas, but it is easily liquefied by  compression and cooling. After liquification, CO$_{2 }$remains in  a closed container as both liquid and gas. When CO$_{2}$ is then  discharged to the atmosphere, most of the liquid expands to  gas. Heat absorbed by the gas during vaporization cools the  remaining liquid to –110 °F, and it becomes a finely divided  white solid, dry ice snow. Carbon dioxide is about 1½ times as heavy as air, which  gives it the ability to replace air above burning surfaces and  maintain a smothering atmosphere. CO$_{2}$ is effective as an  extinguishing agent primarily because it dilutes the air and  reduces the oxygen content so that combustion is no longer  supported. Under certain conditions, some cooling effect  is also realized. CO$_{2}$ is considered only mildly toxic, but  it can cause unconsciousness and death by suffocation if  the victim is allowed to breathe CO$_{2}$ in fire extinguishing  concentrations for 20 to 30 minutes. CO$_{2}$ is not effective as an  extinguishing agent on fires involving chemicals containing  their own oxygen supply, such as cellulose nitrate (used in  some aircraft paints). Also, fires involving magnesium and  titanium cannot be extinguished by CO$_{2}$. 7 through 30 31 through 60 61 through 200 201 through 300 301 through 400 401 through 500 501 through 600 601 through 700 1 2 3 4 5 6 7 8 Passenger capacity No. of extinguishers