[Hillarys Gate Cult]

Isn't halon an oxygen scavenging system, therefore not appropriate for confined occupied areas?

You are correct.

[HangThemHigh]

"Isn't halon an oxygen scavenging system, therefore not appropriate for confined occupied areas?"

"You are correct."

Halon is not an oxygen scavenger, it scavenges free radicals (partially burned fuel, basically). This makes it very effective at fighting fires, even at relatively low Halon concentrations (low enough concentrations that you could get out safely). If the Halon concentration is very high, as it might easily become in a confined space, it can displace oxygen and kill by asphyxiation.