The safe storage of propane cylinders has always been an issue for propane consumers in the residential and industrial LP Gas cylinder markets. It is important to know that the location as well as the position of the cylinder both are part of essential safety practices. Storing propane cylinders with or close to other flammable or combustible materials is considered extremely unsafe and is not advisable under any circumstance. NEVER STORE PROPANE CYLINDERS INDOORS, IN A HOUSE OR GARAGE.
Cylinders awaiting use should be stored in a well ventilated area away from heavy traffic. Propane cylinders stored upright should be placed on a flat surface such as concrete or other non-flammable material that will not collect water. Cylinders that are stored in places that such as damp grass or mud risk exposing the cylinder to conditions that may cause rust and/or pitting that may render the cylinder useless. Storing any propane container indoors is not advisable. It is recommended that a propane bottle be stored outside on a firm surface and away from any source of ignition.
Propane cylinders should always be positioned so that their relief valve is in direct communication with the vapor space of the container. Cylinders that are stored vertically upright will have the relief valve communicating with vapor space. Regarding the cylinder relief valve, it is important to keep the safety relief valve pointed away from anything that escaping propane could come in contact with possibly causing a fire or accident. If cylinders are stored improperly, such as on their side with the relief valve in contact with propane liquid and the safety relief valve opens for any reason, liquid will be escaping instead of vapor posing a much greater danger. In short, be sure the relief valve is communicating with the vapor space of the tank. All consumer propane cylinders should be stored vertically upright in all circumstances.
The pictures below depict unsafe positions of cylinders while in storage. The first 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, consumer propane cylinders such as this should be stored in an upright position. The second picture shows forklift cylinders stored with the relief valve beneath the liquid propane level of the tank. Although industrial type cylinders are allowed to be stored horizontally, they need to be stored with the safety relief valve above the liquid level of the tank if stored on their side, as depicted in the third picture. Additionally, improper storage of bottles can lead to container damage. See pictures of damaged and condemned propane cylinders.