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:
(italicized statement made by me for clarification)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.
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!