Is it (fire) safe?

If you put your backup tapes in a fire safe you probably think it will protect them from fire. But that isn't always the case...

Visualize this. In a locked store room a small portable fire safe sits on a table. In that safe your company's daily backup tapes are stored. Each morning someone places the tapes in the safe, and removes an old set. Every month a set of tapes is transferred off site to your secure storage facility. A simple precaution against fire.

“But is it safe?”

(If you know the film, it helps if you can imagine Lawrence Olivier's maniacal dentist from the film Marathon Man asking the question in a menacing voice.)

A firesafe — that's straightforward isn't it? No need to read the instructions. You just put your tapes in the box (no point in locking it since it's in a locked room already) and if there's a fire that can be extinguished within the one hour the safe is rated for then your backups will survive intact, won't they?


But in this case (which is taken from a recent threat analysis survey I was involved in) probably not. Here's why.

First, it's important to know that there are many types of safes and ratings for safes. A safe rated for protection against theft is not necessarily rated for protection against fire — or vice versa. But this was a “fire safe” so it should have protected the backup tapes against fire, shouldn't it?

No. A fire safe protects its contents by including insulation which changes phase from solid to gas at a particular temperature. Think of it like a kettle full of water. It takes a few minutes to raise the temperature of the kettle to 100°C. At this point the water starts to boil. The temperature of the kettle doesn't rise to 110°C for a long time because the energy from the heat is used to convert water to steam first. Similarly in a fire safe the temperature will rise to a particular point, then not rise any further until a component in the insulation has turned from solid to gas. Then the temperature will rise quickly, and the contents will be destroyed.

A fire safe is therefore designed for a particular maximum internal temperature. Paper and documents can withstand heat up to about 177°C (350°F), but magnetic media will start to fail at about 52°C (125°F). A fire safe designed to contain magnetic media must therefore prevent the temperature rising above 52°C (125°F) to be effective. A media safe can be used for documents, but not vice versa. The safe in question was of the wrong sort. The internal temperature would have rapidly risen to about 177°C and destroyed the contents. A media safe should have an Underwriter's Laboratory UL 72 Class 125 (i.e. 125°F) rating.

So substitute a media fire safe for a document fire safe and ask the question again, “Is it safe?”

No. Remember the description of how fire safes work. When the temperature rises, moisture is released to absorb the energy from the fire. Some fire safes requrire the contents to be placed in protective containers to avoid damage from this moisture.

So nip down to the supermarket, buy some cheap dishwasher-safe plastic boxes, and put the tapes inside.

“So is it safe?”

Not yet.

To be effective, the fire safe needs to be locked. The lock isn't there to prevent theft. Indeed, the typical firesafe lock isn't designed to deter the determined criminal with a paperclip, let alone with a hammer and screwdriver. The safe needs to be locked so it won't burst open if it falls, is knocked around by the water from a fire hose, or when the box expands due to the heat.

Finally it should be on the floor. Preferably a ground floor. There are two reasons for this. One reason is to prevent any damage to the heads of firemen who happen to be standing underneath it when the floor collapses. The other is to prevent damage to the hot safe itself when it is dropped. It (and it's contents) may not survive the fall.

“So is it safe now?”

Yes. But only as safe as it was rated to be. For media safes, a safe is typically only rated to be exposed to fire for half an hour or an hour. Perhaps enough for the fire department to arrive and extinguish a small fire, but probably not enough if the fire safe is located in a hot spot (such as a storage room full of flammable materials) of a well-established fire.

So don't keep the safe in a room full of flammable materials, and make sure those fire detectors and sprinklers are working too!

26 June 2005

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