MacGregorSailors.com

As far as dangerous fuel goes, good old gasoline is the most dangerous. It is followed and not too closely by propane, then alcohol. Gasoline is worst because the vapors are heaver than air and can also pool in low areas. Gas has a much wider ignition bandwidth than propane (fuel to air mixture that is explosive). Gasoline has more energy per volume and we carry a lot of it on board (20 gallons vs 2 quarts). Propane generally has a bad reputation just because it is under pressure, where gasoline is not. Propane has a scent added to let you know it is there, not so with gasoline. The only boat I have ever seen burn to the waterline was due to a gasoline fuel leak. The boat was a total loss in less than 5 minutes. I always keep gasoline and propane topside and alcohol below deck. My other sport (hence the name) involves vast quantities of propane used with great care.

You mean you don't have a giant Origo alcohol stove on your hot air balloon?
Just think how much safer that would be, since it probably would not get off the ground!

..

When it too calm to sail, fly balloons. When it it too windy to fly, then sail. Besides launching or landing a balloon is like flying a 9000 square foot spinaker. It can definetly spill your beer!

Reviving an older thread on the always contentious topic of Propane in the cabin ...

I just happened to see this device on eBay, also carried at Boatersworld ($99). It comes with one remote sensor, additional sensors available ($25 ea). I suppose one could mount several sensors in our various bilge compartments to monitor any potential leaks from cabin-mounted appliances.

Marine Technologies SA-1 Gas Fume Detector

Keep your friends and family safe! This affordable unit detects dangerous fuel vapors, propane, methane, hydrogen (from batteries), and many other explosive vapors. Available in dash mount unit. 1 fume sensor is included, but an additional sensor can be added to either unit for monitoring of a propane locker or gen-set area. On/Off/Test switch insures smooth operation. 2 1/8" diameter.

Also stumbled across this new product at the MacOwners site.
The tank is translucent, so you can see the qty of propane remaining:

[b][u]MacOwners' page[/u][/b] wrote: Lightweight composite propane tank -- 30% Lighter Than Steel Tanks! ($99)

These lightweight, strong, fire resistant propane tanks are the perfect replacement for heavy, clunky metal tanks. Meets or exceeds the same fire standards as aluminum or steel tanks. Highly regulated and extensively tested safety features let you use these tanks with complete confidence. Features:

• Cylinders are equipped with standard UL Listed OPD (overfill protection device) valves
• Composite cylinders are DOT (Dept. of Tranportation) approved
• Corrosion free
• Stackable
• See how much fuel is in the tank
• 5 gallon, #20lb capacity, 11 pounds empty, 18 inches high x 12.4 inches wide
• 2.5 gallon #10lb capacity, 9.7 in. diameter, 17.3 in. tall
• Cylinder is fiberglass, casing is a poly ABS material