Some are better than others. You need to do the research and understand what they do from a cost benefit stand point. But, I'll leave the burning to death versus shortening your life a few years decision up to you.
That's why you get Halon, and only Halon, for cockpit use. Pure 1301 is the safest, but hard to find. More common is a 1301/1211 mix. 1211 is toxic above a certain concentration, so you'll see "minimum room volume" limitation on the bottle. Make sure you get a bottle with a smaller minimum volume than your cabin volume (may take some research, but the data are available). Everything else (CO2, dry chem, HFC's, HCFC's, Halotron, etc), is a lot worse for toxicity/lethality and effectiveness in the cockpit environment, which is why aircraft cabin/cockpit use is the one big exception to the Halon ban.
"A lot" is right -- about ten times the effective extinguishment concentration for Halon 1301. However, with 1211, the toxicity level is only about three times the effective extinguishment concentration, which is why that minimum room volume limit is important.
One of the problems in discussing Halons is that there are over a dozen different compounds called "Halon", some of which (like 2402) are highly toxic, and others of which are virtually non-toxic (like 1301). 1301 was the "silver bullet" in that it wasn't toxic in any concentration (suffocation not being the same as toxicity) and extinguishes fires in pretty low concentrations (2-6%, depending on the type of fire). The only problem with 1301 is that due to its low boiling point, it's primarily a volume fill agent, and loses effectiveness when you're trying to put out a point or streaming fire rather than a large volume fire. That's why 1211 is added to the mix for aircraft extinguisher. While it adds streaming capability, it also adds toxicity, so it's used in a mix with 1301 to maximize effectiveness while keeping toxicity to an acceptable level.
Neither pure 1211 nor any HCFC ("Halotron" and other names) extinguisher is a good idea in a cockpit (or any other enclosed space unless you can bail out). 1211 is too toxic, and HCFC's will probably produce a lethal post-fire environment (ask your doctor about exposure to hydrofluoric acid, which is a pyrolization product of the exposure of HCFC's in an effective concentration to heat). The best choice for both toxicity and effectiveness for all foreseeable cockpit fires remains a 1301/1211 mix as long as the minimum room volume limit is observed.
With Halotron, it is only the pyrolized byproducts which are really nasty, and you don't get those without exposure of the agent to the heat of the fire. The neat agent is not particularly toxic. Toxic effects from neat 1211 begin at about 2%, with one-minute exposure effects at about 4%, and lethality is somewhere well above 6%. The good news is that it kills the fire so fast, the residual pyrolysis product concentrations are relatively low. So, one gets you on the front end, and the other on the back end. 1301, however doesn't get you on either end.
Yes. It's hard to find pure 1301 units, and for the reasons discussed above you probably want a 1301/1211 mix anyway, but it is legal for this application.
Well, all the legal available replacements. 13001 is actually more effective, but not being produced because of the cardiac sensitization issues.
Don't get caught by EPA with that stuff.
You were told wrong. Breathing halon over the short term hasn't been shown to have any ill effects. The real concern with flood systems is that you might have areas where there is insufficient air to breath properly. However over the average, Halon doesn't need to be in very high concentrations to be effective. Contrary to what some people tell you, it does NOT displace the oxygen to below the free burning level. It interferes with the fire chemical reaction.
No, it's pretty much the safest of most of the agents.
Again, that's strictly for Halon 1301. H2402 can be about a five-stepper, and H1211 can cause significant effects within a minute at 4% concentration. Of course, only H1301 is used in occupied space flooding systems, so that may not affect the specific case under discussion, but please beware of using the word "halon" in any blanket statements without specifying which Halon you are discussing -- that's how these rumors and OWT's start.
I was told to get out of the room before the doors locked (automatically). If you cannot get out in time, then lie down on the floor and don't panic because all the oxygen will be displaced. Someone will be there to help when you wake up. That was a few decades ago. I hope they have improved the technology.
I'm not sure lying on the floor is a good idea, since the molecular weight of H1301 is about five times that of air -- which means it's going to settle to the ground. Or maybe they just wanted to make sure you wouldn't fall and hurt yourself when you passed out.
Have you compared that 156 to the actual cabin volume of your airplane? I suspect a lot of light singles are less than 156 cu ft net volume (after you exclude seats and other items).
Let's get something strait because there is a lot of misinformation out there. And if you need my background, I was a firefighter up in Maine back in the 1990s, then a merchant marine officer and now a Navy Surface Warfare Officer. I have trained on, worked with and used most of the portable and fixed systems out there. First off, Halon does not displace O2. That is what CO2 extinguishers do - they stop the fire by removing the oxygen. Because of that, you have to be careful about using CO2 in confined spaces and when used in fixed systems (like merchant ship engine rooms), you must evacuate....or die. Halon does not work that way. Halon chemically interrupts the chain reaction that occurs in combustion, thus putting the fire out. There is some debate about how toxic the by products of halon use on fire are (which may be due to the fact that there are a few varieties of Halon). Bottom line is, you won't die from Halon discharge, but depending on how much of the byproducts you inhale, you may have some health complications later down the road (which is what Michael was alluding to).
OK, not the way water displaces air, but it does reduce the O2 concentration in the space, and when the H1301 concentration gets high enough (around 600,000 ppm of H1301) to drive the O2 concentration low enough, people start to suffocate.
That is also why you need vastly higher concentration of CO2 to kill a fire, and why it's such a lethal threat -- you have to get the CO2 concentration to the same level that suffocates people in order to suffocate the fire. OTOH, brominated Halons kill the fire at concentrations an order of magnitude lower because they interfere with the chemical kinetics of the combustion process. So, you don't need to dump suffocating concentrations of brominated Halons to kill fires, and that's why they are the agent of choice for occupied spaces.
For 1301 that's true. For other Halons, that's not true. That's why you have to know which Halon it is with which we're dealing.
Unless it's 2402, in which case you're dead. Beware of Halon systems behind where the Iron Curtain used to be, because they used 2402 in a lot of systems including aircraft engine compartments.
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You've extracted a single line out of context to support your contention that "There are no federal or state regulations prohibiting the buying, selling or use of Halon extinguishers." Al I was trying to say is that it's more complicated than you made it sound.
One could, and many did back in the 90's. We won the argument as far as airplanes were concerned. That's why they're still legal for that use today. But for things like big computer rooms and oil processing facilities, all new installations are things like FM-227.First off... Great thread and wonderful info....
As for the Ozone depleting issues.... Seems to me the VERY small fraction of Halon extinguishers out there present a miniscule problem.. And that is based on the fact they will be deployed... An even smaller fraction are actually discharged to put out a fire so the ozone risk is almost impossible to access...
One could argue that the inferno created by a plane hitting the earth and going up in a fireball will cause more enviromental damage then if a pilot discharges a small extinguisher to put out a inflight fire and get the plane on the ground safely..
