These are basically small concrete boxes sunk into the ground. They're only meant to stick out a bushfire for a few hours.
You could probably just keep a few bottles of oxygen or a carbon dioxide scrubber stashed in there, just in case. If you can spend $10,000 on one of these bunkers, spending a few hundred more isn't going to make a difference.
Anything longer than a few hours would get dicey anyway without room to move around, without room to stash water or food, without a toilet or beds.
These are basically small concrete boxes sunk into the ground. They're only meant to stick out a bushfire for a few hours.
You could probably just keep a few bottles of oxygen or a carbon dioxide scrubber stashed in there, just in case. If you can spend $10,000 on one of these bunkers, spending a few hundred more isn't going to make a difference.
Anything longer than a few hours would get dicey anyway without room to move around, without room to stash water or food, without a toilet or beds.