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In this event, the crew of a 777 responded to a spurious cargo fire indication by activating the fire suppression system, which suffocates the cargo area. Presumably any pets held there would have died as a result.

What are the SOPs for fire suppression when carrying pets in the cargo hold? Are they held in a separate compartment?

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    $\begingroup$ Don't think there is one. And to be brutally honest, as much as those who love their pets will disagree: The value of an animal compared to hundreds of humans will always be less, so in the event of a fire, the suppression system will be triggered. According to this blog, carrying pets in the cargo hold should be a last resort thing. $\endgroup$ – SentryRaven Jun 26 '15 at 12:04
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    $\begingroup$ After a bit of further research, there seems to be the option of discharging a slightly different agent for cases where animals or perishable goods are transported. See also this PDF. $\endgroup$ – SentryRaven Jun 26 '15 at 12:10
  • $\begingroup$ Not sure if the above sources warrant a complete answer though. $\endgroup$ – SentryRaven Jun 26 '15 at 12:15
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    $\begingroup$ Cargo fire is the worst kind of fire and is easily capable of bringing down the whole plane unlike an engine fire. If EICAS indicates a fire back there I'm blowing the bottles and landing at the nearest suitable. Pets are not a consideration over the human souls on board. $\endgroup$ – casey Jun 27 '15 at 1:41
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    $\begingroup$ As a matter of historical trivia, 727-100s had a aft lower cargo hold that was normally heated, and that was where pets were often carried.There was a switch on the f.e. panel that controlled whether or not it was heated. The switch was colloquially referred to as the "dog killer switch." $\endgroup$ – Terry Jul 5 '15 at 21:45
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What happens to live animals in cargo depends on the type of airplane and the class of cargo compartment they're traveling in. For a typical passenger airliner, if you check your animal as baggage, they're going into the "lower lobe cargo compartment" under the cabin floor. This is classified as a Class C compartment, which essentially means that the crew have no access to it in flight, so it must contain fire detection and extinguishing systems. The applicable regulation is 14 CFR 25.857.

Quite simply, there are no considerations for live animals in Class C compartments. If you look in Boeing cargo fire checklists (copyrighted so can't post here, but you might get lucky with Google), the steps in the checklist deal with discharging the Halon into the cargo compartment and adjusting the pressurization system to minimize flow into the cargo compartment. This helps maintain the minimum required Halon concentration to provide the first big knockdown blast to stop the fire from spreading, and then maintain a low-level concentration to keep it suppressed for the length of the diversion to a landing. Unfortunately, that means any live animals will suffocate since Halon displaces oxygen.

For dedicated freighters such as the 747-400F/747-8F/777F etc., the main deck area is considered a Class E cargo compartment, which doesn't have a fire extinguishing system. If a fire is detected here, the procedure is to depressurize the entire cabin and minimize/cutoff air flow to the main deck area, and climb/descend to a mid-altitude (somewhere in the 24,000-28,000' range depending on the airplane) to minimize oxygen and help suppress the fire. If animals are transported here, rather than the Class C lower lobe compartments, they may survive. They may become hypoxic and lose consciousness, but there's no Halon to suffocate them. Depending on the length of time for the diversion to safe landing site, the lack of oxygen may be a serious issue for some animals just as it can be for humans, but that's a guess as I'm not a vet.

Bottom line is if you're taking your pet with you on a commercial flight, the safest, most comfortable, and least traumatic place for them is with you as a carry-on item.

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    $\begingroup$ I worked in IT in the '80s, and computer rooms were routinely protected with Halon. We were taught that Halon was relatively safe. A number of my colleagues were in the computer room when it was accidentally dumped into a room with at least 6 people working in it. They were all fine. IIRC, we used a concentration of 7% Halon 1301, which cannot displace all the oxygen. Halon works by interfering with the chemical reaction that is fire, $\endgroup$ – user19474 Jul 4 '16 at 15:48
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    $\begingroup$ As said in the other comment, only a low concentration of halon is needed to extinguish a fire. This is because it inhibits the chemical reactions during combustion, while there is plenty of oxygen around. That's great, since humans and animals can still breathe that air. BUT: there is still the smoke in the air, and the stuff produced by the halon in the fire is also nasty. That means, an animal will not die due to the lack of oxygen, but may be due to the gases from the combustion. $\endgroup$ – sweber Apr 21 '18 at 20:49

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