[cyberax]

This really is a non-issue. If you're at the point where toxins from halon pyrolysis are a problem, then you're likely already dead from other factors (heat, smoke, etc.).

Halon can works even at concentrations of just 2-5% by volume. This is entirely safe to breathe for humans. There's a video of a person discharging a halon extinguisher in a room, and then proceeding to try to light a cigarette. The matches go out immediately after striking the matchbox and the lighter can't even ignite.

CO2 extinguishers are really worse, they need to displace most of the oxygen to be effective. Unfortunately, humans also need this oxygen.

In addition, CO2 stream can cool the burning material, but it can also spread it (so be careful if you use it on burning liquids).

[buildsjets]

In testing aircraft installations, the FAA requires you to demonstrate 6% concentration of Halon 1301 at 12 FAA chosen locations in a compartment for 0.5 seconds, simultaneously, when the test is run at sea level and standard temperature. This is to allow for the fact that the halon bottles may be cold soaked down to -60F and that the system needs to be effective at density altitudes down to -1000 feet.

[jabl]

Engine rooms in ships typically have CO2 systems. There's been several fatalities when crew have reentered the space before the CO2 has been ventilated away. Made worse by CO2 being heavier than air so it can remain in some crawlspace under the engine frame or such.

[cyberax]

Yep. Found that safety video: https://youtu.be/NrP5-E9jmas?t=344 - I was misremembering it a bit.

It's really unfortunate that halon is so dangerous for the ozone layer, none of the replacements are as good as it was.

[jabl]

High-pressure water mist systems seem pretty good, including being usable in spaces with lots of electrical stuff like machine rooms and data centers.

https://www.marioff.com/en/

[cyberax]

Second 292 for the demo.