If you plan on having the medium survive your house burning down, it'll either have to be something really exotic(CNCed cuneiform tablets?) or something boring inside a sufficiently fireproof safe (which can get costly; but are a well recognized product category).
Fireproof safes (actually fire resistant) are not what you want to use for storing electronics or cd/dvd/bd media.
You specifically want a fire resistant "media" or "data" safe.
The difference is that "fireproof" safes are intended to prevent paper from charring/burning, so their design allows for internal temperatures that are high enough to cook your electronics. Media/data safes maintain a significantly lower interior temperature (and humidity), which safeguards your relatively fragile electronic hardware.
And it's not just enough to avoid high temperatures, your safe needs to be sealed against gasses.
In a home fire, you have all types of corrosive and unpleasant chemicals that are created from burning plastics, toilet cleaner, etc.
Those chemicals will generally attack any metal and plastic that they come into contact with (YMMV).
TLDR: You get what you pay for, so get the right thing.