Let’s begin with the number and location of hand-held fire extinguishers — Page 160, Lesson 255

I want to walk you through the operational requirements for hand-held fire extinguishers in an aeroplane. We’ll start with the core principle: the extinguisher must be used on the correct type of fire, and you must be aware of the hazards that come with using extinguishers inside the closed environment of the aeroplane. Let’s begin with the number and location of hand-held fire extinguishers. The regulation says the number and location should be such that they provide adequate availability for use. When deciding how many and where to put them, you have to account for three main factors: first, the number and size of passenger compartments; second, the need to minimise the hazards of toxic gas concentrations; and third, the locations of toilets, galleys, and similar areas. These considerations may result in the number of extinguishers being greater than the minimum specified — so the minimum is just a baseline, not a target. Now, the flight deck extinguisher. There must be at least one extinguisher installed on the flight deck. That extinguisher must be Halon 1211 — the chemical name is bromochlorodifluoromethane, with the formula CBrClF₂. This extinguisher must be suitable for both flammable fluid fires and electrical equipment fires. So it’s a multi-purpose unit for the two most likely fire types on the flight deck. Additional extinguishers may be required for the protection of other compartments that are accessible to the crew in flight. There is an important restriction on dry chemical fire extinguishers. They should not be used on the flight deck or in any compartment that is not separated from the flight deck. Why? Two reasons. First, the discharge has an adverse effect on vision — it can blind you temporarily. Second, even if the dry chemical is non-conductive, the chemical residues can interfere with electrical contacts. So dry chemical is prohibited in those areas. Now, for galleys: if a galley is not located on the main passenger deck, at least one extinguisher must be provided at that galley location. For cargo and passenger compartments: at least one readily accessible extinguisher must be available in each class A or class B cargo or passenger compartment, and also in each class E cargo compartment that is accessible to the crew in flight. Finally, the excerpt mentions a table that details the number of extinguishers which must be conveniently located in the passenger compartment. That table gives the specific minimum numbers based on passenger capacity, but the text here only introduces it — the actual numbers are in the table itself. To summarise: you need Halon 1211 on the flight deck for flammable fluid and electrical fires; no dry chemical on the flight deck or connected compartments; and extinguishers positioned based on compartment size, toxic gas hazard, and locations of toilets and galleys. The goal is adequate availability while minimising the hazards of using extinguishers in a closed environment.