Propane is a by-product of natural gas processing and petroleum refining; it is commonly used as a fuel for engines, barbecues, portable stoves, residential heating and can be used for lighting. I consider propane the best fuel to store in bulk. It is the safest, easiest to store and has a very long shelf life. Propane will last as long as the container remains intact.
Propane is stored as a liquid when under pressure in the tanks. Upon being released to the atmosphere, it vaporizes into a gas. While it is the safest fuel to store, it still has a certain degree of danger. The tanks should be store in the position that the manufacture specifies.
An example of the incorrect storage of propane tanks.
The picture below depicts an unsafe storage position for small propane cylinders. The picture assumes that the 20 lb. cylinder has a little over 50% propane. Even with the tank around half full, the liquid inside is above the level of the safety relief valve. The relief valve needs to be in communication with the vapor space of the cylinder in case it opens. For this reason, all consumer propane cylinders such as this should be stored in an upright position. This would normally be the 4 – 40 pound tanks. Larger tanks of propane should be placed in a location per the manufactures recommendation.
Propane tanks are readily available up to a 1000 or more gallons and in most parts of the US are easy to get filled. Many areas have few regulations on the locations of the tanks and the condition of storage. Since propane is a heavier then air gas and will flow along the contours of the ground like water, a big consideration is where to place your tanks. Place your tank downhill if possible from your residence and other important locations in case of a leak. I have seen it flow downhill and accumulate under a building until it reached an ignition source. The resulting explosion destroyed the building.
If you are on currently on natural gas and are thinking of converting to propane in an emergency, contact your propane company and get the correct size orifices for propane. They are different from natural gas and if you fail to change them, it can create a serious hazard.
I like propane as a fuel and have a duel fuel truck that runs on both propane and gasoline. We also have tri fuel generators that will run on propane, natural gas and gasoline. If you are thinking of converting vehicles or generators to propane get the conversion kits beforehand, without them; this would be a very difficult conversion to make.
Propane is an efficient fuel that is easy to store and safer than most if you follow the rules. Here are some links to previous posts that I have written on this subject. The Correct Fitting for 4-40 Pound Propane Tanks, What Happens When Your Propane System Fails and How do You Prevent It , Tri-Fuel Generator Conversions.
Where I live you can still get propane cheaper than gasoline and it does not have the short shelf life of modern gasoline.