If items in a fireproof safe are purposefully set on fire with a fully closed and locked safe, are contents outside of the safe generally safe from fire?

The safe can be placed in a secluded spot and on stone.

Additionally, in general, what digital signals (if any, reliably) are able to penetrate a locked safe?

Probably yeah. A fireproof safe will be airtight, so the system can only produce as much energy as whatever reagents you put inside.

That really depends on the safe but for the most part it should be. It would probably ruin the safe as the inside is probably not fire resistant but also the fire would probably choke out as the safe should be airtight. As for signal penetration, again depends on the safe but I believe that most safes have some layer of thick metal, which should block all signals.

I assume you mean radio frequencies, and the answer is basically none. A grounded fireproof safe is basically a perfect faraday cage.

EDIT: Ok, I actually have a pedantic answer for this. If you put a microphone on a device inside the safe, you can signal it from outside by sending it vibrations, and you could encode a message in binary and thus technically send it a "digital signal". If you wanted to be a little more analog you could use Morse code :)

Ok, that’s a good point and something appreciated insight.

Yes. Ok well that complicates things, but I suppose a piece of string small enough may be able to dangle out of the closed door and maybe be slightly moved…

I know nothing about safes, let alone fireproof safes, but I'd guess that pressure may be an issue, if not a lack of oxygen for the fire to burn through.

Thanks a lot

What you want, if it needs refractory-cement, Kaowool, or whatever the insulation in the walls of fire-safes is, is called a Forge or an Incinerator, maybe a Kiln or a Heat-soak Furnace, and no, an off-the-shelf Fire-safe is far from sufficient without abusrdist-levels of modification.

The heat needs somewhere to go, and those safes, the plastic home-and-office-grade ones anyways, are designed to take external pressure, not hold it in. In-fact, part of why they work is that the oxygen get's sucked-out by the fire outside -they generally aren't air-tight, save maybe the "flood-safe" ones ... which I still would be surprised to see protect anything versus prolonged submersion.

Even if you used an electric heating-element and seal the gap you need for that perfectly, you're going to out-gas the plastics and insulation, destroying the integrity of the safe and contaminating the area with toxic fumes, long before the contents are singed-enough to cause much damage without additional oxygen. Once you've got an open flame, your electric heating-element is fucked, so while you could maybe BS a fire-safe to suit your purpose, its one-time-use and closing/locking it is working against you every step of the way.

If it has to be cheap/free, and low-technical-difficulty, there's Primitivist channels on youtube that will show you how to make a forge from clay and/or clay-brick and mud.

I guess if heat-alone would do what you want, a dutch-oven over an open fire could do, or a charcoal-chimney-starter if the items are small-enough. For PID-document destruction, I use a fire-pit, or rather, I use bills and reciepts to light kindling, but I usually have enough of both that you could almost call the wood in the pit an after-thought.

Very good info and your comment has convinced me that fire is not the solution. I think I know what I can do instead, actually.

For hard-drive and chip-storage destruction, its hard to beat a drill or a hydraulic press. Holes, or snapping the storage-medium in half will generally do. From there to recyclers or landfill, either is less toxic to the environment than burning the stuff in a PC or phone.

Thanks, might well be something I need to look into depending on my decision.

Note, @disorderly@lemmy.world is referring to metal-safes, not the plastic file-safe crap you'll find in Walmart.

Notice that a battery fire will produce it's own oxygen.

Well if the safe is airtight then the fire will stop as soon as the safe is closed because there needs to be oxygen for fire to spread

There are other oxidizing agents that xan maintain fire.

What are you lighting on fire? Why are you burning it? What's the problem you're trying to solve?

Let’s say you put some slow burning rocket fuel in there, and it ignites one day. The inside of the safe will probably melt, smoke will ruin your entire house, but it shouldn’t burn down the whole thing.

Actually, this brings up an interesting alternate use for an old safe like that. If your old fireproof safe is broken, or you lost the key or whatever, you could turn it into a fireplace of sorts. Just flip it the door side up, throw in some logs and a place a large pan on top. May look a bit ghetto style, but who cares as long as the wok veggies and meat taste good.

the fire will die as there will be no oxygen in the safe.

If you fill a safe with rocket fuel and ignite it, the safe is not guaranteed to contain the result.

Like petrol?

It's my rocket fuel, and it was either the safe or the toilet, alright

Just a reminder these safes are not actually fireproof. They are fire resistant and people should check what they are rated for before buying.

Just put an oxygen tank in it too, easy!

You won't even have to worry about fire then!

Your fire is gonna be significantly limited by lack of oxygen. See how long a tiny candle flame stays lit under a cup. A bigger flame will fizzle out even faster. The paper in the safe won't even have a chance to burn, just singe.

Do we dare ask?

Depends. A basically old wood fire? No. But here is other nasty stuff that does not 'burn' as we think of it but still produces enormous heat in exothermic reactions that do not need oxygen to sustain themselves.

If you plan to securely store such material look at appropriate chemical supply storage, not safes.

What is the fireproof safe for?