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In most states it is illegal to store propane tanks indoors. This is because of the way propane behaves in the case of a leak. Although it is stored in the tank in liquid form, propane becomes a gas when it is released. Propane gas is heavier than air, so it will sink to the lowest available space. Leaking tanks inside a home would promptly fill the basement with the flammable gas where a spark (such as the ignition on a water heater or electric furnace) would trigger an explosion.
Even when stored outdoors, a propane leak is dangerous. For this reason, a chemical compound is added to the propane so that it can be detected by smell (propane naturally has very little scent).
Though not regulated by law, tanks should be stored upright and kept clean. In some locales it is required that tanks be kept upright during transport. Rusty or damaged tanks should be replaced. -
One of the dangers of propane tank use involves the extreme pressure under which the liquid propane is kept. Due to thermal expansion, this pressure rises as the temperature of the environment goes up. A tank stored just 80 percent full in 70-degree weather can have an internal pressure greater than 120 pounds per square inch.
For this reason, propane tanks are never filled completely, allowing room for expansion. In addition, propane tank valves feature a pressure release feature that allows gas to leak out when pressure gets too high (around 325 psi). This is because even gradual leakage is less dangerous than an explosion that could occur if a tank ruptures due to excessive pressure. -
In the late 1990s, the National Fire Prevention Association strengthened its regulation of propane tank valves. The new regulations called for the use of overfill protection devices. Valves in compliance are labeled "OPD" and can be identified by their three-lobed handles which are visibly different from traditional propane tank valve handles.
The purpose of overfill protection is to prevent the tank from being more than 80 percent filled with gas. This ensures that there is adequate extra space in the tank so that the propane can expand due to variations in temperature and atmospheric pressure without causing leakage.
Like the old valves, overfill protection valves use an internal float to measure the level of propane in the tank. As OPD valves were mandated, propane buyers were forced to trade in their tanks for new ones with the proper valves. -
Propane is sold in variously sized cylinders for its many applications. In certain cases, laws apply to a specific range of cylinder sizes. In some states, small (portable) cylinders must be plugged with a special device during transport. State and local codes also regulate how much propane can be transported in certain types of vehicles, with limits on how many tanks can be carried in an enclosed vehicle.
Large tanks for household heating are governed by different regulations. These generally include homeowners maintaining the shutoff valve and ensuring that the tank is regularly inspected for leaks. Electronic propane gas detectors are not mandatory but may be a suggested measure in areas where large propane tanks are common. -
There are also laws governing the safe disposal of propane tanks. In general, tanks must be turned over to an authorized propane distributor for disposal. Since most tanks are refilled on a trade-in basis, old tanks can be easily cycled out of circulation. Laws require propane sellers to inspect all returning tanks and label them with an inspection date. Only cylinders that have passed inspection within a certain time limit may be legally refilled.
Although the required procedure for disposing of an old tank varies from state to state, it is always illegal to place a propane cylinder in the trash, even if it is empty. Special municipal collections are sometimes held to remove old cylinders from local households.
