Compressed gas cylinders must be respected for their potential to cause injuries and property damage and disruption to operations due to leaks of toxic, flammable, and asphyxiating compressed gas, explosions and pressure release of pressurized systems, and the sheer kinetic energy resulting in any catastrophic failure of a gas cylinder.
Only trained and qualified personnel shall be allowed to use compressed and liquefied gases. Training should include the associated hazards of the materials, necessary safety precautions, proper operation of the cylinder/regulator/related equipment, personal protective equipment (PPE) and emergency response procedures. UW Chemical Safety Office provides general training on gas cylinder safety.
Types of Hazards
In addition to physical hazards inherent in all gas cylinder, the contents of each cylinder has inherent hazards depending on the properties. Understanding the hazards determines specific storage and use practices, regulatory requirements, and campus policies. Hazard information should be clearly indicated on each cylinder. The contents of cylinders fall into one (or more) of the following categories:
- Flammable or Combustible
- Poisonous or Toxic
- Combination of Hazards
UW Gas Policy Policy
The University of Wisconsin–Madison requires approval by the Environment, Health & Safety Department (EH&S) prior to both the initial purchase and initial use of the high-hazard gases falling into the categories listed below. Approval is not required for re-orders of gas cylinders as long as their use has not changed. This policy is designed to ensure that the users have performed a hazard assessment, enacted appropriate engineering controls, and have received the necessary training prior to using the gases. It is the responsibility of the individual who intends to use a high-hazard gas to contact the Chemical Safety Office. The gases in the following hazard classes are subject to this policy:
- All gases that are designated by Global Harmonization System (GHS) classification as Category 1 or 2 for acute toxicity;
- All corrosive gases as designated by GHS, including both gases that are corrosive to the skin and/or corrosive to metal;
- All pyrophoric gases.
Additional information can be found in Appendix A1 of the Campus Chemical Hygiene Plan. Requests for assessments can be submitted through this form.
Gas Cylinder Storage Requirements
Cylinders must be stored in an upright position with the cylinder caps in place and must be secured with a chain or strap above the midpoint, but below the shoulder of the cylinder. Cylinders less than 18 inches tall may be secured by approved stands or wall brackets. Oxidizers and fuel gases must be separated by at least 20 feet, or by a non-combustible wall at least 5 feet high with at least a one hour fire rating. Flammables must be kept at least 20 feet from all sources of ignition. Additional restrictions and best practices can be found in the Gas Cylinder Safety document.
Cylinder hand trucks are the only acceptable means of transporting gas cylinders within a building and to an appropriate vehicle. Cylinder hand trucks must have a strapping or locking mechanism to ensure the gas cylinders cannot move during transport. Cylinders must have a safety cap secured at all times in transport or storage.
Short-term vehicle transportation of cylinders is only allowed in UW–Madison approved vehicles. The cylinder must be strapped or locked to the inside of the vehicles in a vertical orientation. Cylinders must meet the Department of Transportation’s requirements for labeling, marking, and placarding. The labeling on most current cylinders meet the DOT requirements and it is therefore important not to remove the labels. Remove the cylinder from the vehicle as soon as you have reached your destination and place it in proper storage. Contact UW Chemical Safety Office if you have questions or assistance with transportation of cylinders.
Cylinder Returns and Disposal
While the contents of gas cylinders are purchased from vendors, the cylinders themselves are typically rented from the corresponding vendor, with an associated demurage (rental cost). Empty or unused cylinders should be returned to vendors in a timely fashion. If unable to return a cylinder to the vendor, contact chemical safety for disposal. Due to shipping regulations and restrictions, cylinders of high-hazard gases can be expensive to return to the vendor. Return shipping costs should be budgeted prior to purchase. Contact Chemical Safety if you have disposal or cylinder return questions.
Flammable, oxidizing, and pyrophoric gases are subject to specific limits on the allowable quantities and requirements for storage and use. Information on the allowable quantities can be found in Appendix D of the Campus Chemical Hygiene Plan.
Lecture bottles are small compressed gas cylinders (typically 12–18 inches long and 1–3 inches in diameter) and are used in laboratories working with small quantities of gases or specialty gases. These are still subject to the same regulatory requirements but have special concerns with the use, storage, and disposal.
Additional Safety and Risk-Mitigation Devices
It is the responsibility of all users of gas cylinders to reduce, when possible, the risks associated with hazardous gas cylinders. A number of simple engineering controls are available to researchers. These devices including demand flow regulators, excess flow valves, restrictive flow orifices, and purge assemblies. Contact Chemical Safety to discuss the use and benefits of these devices.