Propane safety, direct from the National Fire Protection Association

[MikeAurelius]

I recently sent an e-mail message to the NFPA discussing the use of 20# and similar propane tanks and asking about the possibility of BLEVE (boiling liquid expanding vapor explosion) incident with a tank that small.

Here is their response, and I found it to be highly enlightening:

The American National Standard for storage and use of propane cylinders is NFPA 58-2004, Liquified Petrleum Gas Code, which is adopted in all 50 states. NFPQ 58 does not allow 20# propane cylinders to be used or stored in residences. This includes garages attached to residences, and detached garages. Use is permitted to a limited degree in industrial buildings, but only where it would be impractical to locate the cylinder outdoors and pipe the gas in.

The major hazard is not BLEVE, but overheating and release of the propane torch fire, which can extend 20 ft from a cylinder (from the pressure release valve). This can spread fire horizontally, and can be a significant threat to firefighters.

(italicized statement made by me for clarification)

This corrects several statements I and others have made in the past as to what defines a "garage", and as you can see, also covers detacted garages and apparently commercial buildings as well.

As is stated, even storing your bbq with the tank attached inside your garage when not in use is in violation of NFPA 58.

I urge everyone to keep the above information in mind as you safely work on your lampworking projects!

[Vince]

There isn't anything new here as these prohibitions have been part of NFPA 58 for a long time and Mike and I have frequently stressed them. The distinction being made in the reply is that it is considered that the volume of LP gas in a 20# cylinder could vent through the relief valve faster than the pressure increase could rupture the tank causing a BLEVE. Since there are only 20# of propane to deal with, the tank would soon be empty and all chances of a BLEVE removed. That doesn't mean that serious damage and deaths couldn't occur by the horizontal flame sheet as they certainly could and most likely would. A fire from the contents of a 20# tank would incinerate virtually everything in a normal home or similar sized building and kill anyone or anything unlucky enough to be in its path. It is extremely dangerous as Mike and I have stated in this forum many, many times.

BLEVEs typically occur in larger tank storage systems, such as bulk storage tanks and tank cars because there the relief systems frequently can't vent faster than the pressure builds up from the many tons of boiling LP gas available. These are awesome events and cause widespread destruction, often devastating entire neighborhoods and throwing large, heavy debris as far away as a mile.

The net is: Don't keep propane tanks in your home or garage. Keep them outside. They are dangerous.

What constitutes a commercial building varies with jurisdiction and the class of occupancy defined in the permits. Even there, should it be permitted, storing propane inside the building isn't less dangerous, it is just permitted. Permitted does NOT mean that something is less dangerous but simply that a judgment call has been made that the risk to life and limb is somewhat less because of the uses to which the building is being put and the type and skill of people occupying it. "Permitted" is not a synonym for "safe".

Vince