Fortunately, the explosion occurred at night and no one was present in the laboratory when a small steel compressed gas lecture bottle ruptured violently, destroying the hood it was stored in.1 It could have been much worse. Although the cause was never positively determined, it is suspected that chemical reactions, internal corrosion, and/or contamination led to the blast. The cause is not important. What is important is that compressed gas accidents occur too frequently and usually produce serious consequences. The Safety Guys feel this warrants a review of our use and storage of compressed gases in laboratory settings.
We know most laboratory facilities use a wide variety of compressed gases. These can range from the classic inert gases like nitrogen, carbon dioxide, and argon to the highly flammable like hydrogen, acetylene, and oxygen—and the one involved in the accident above. They are used by maintenance personnel for welding and by researchers for animal anesthesia, among many others.
The hazards involved in compressed gas use run the gamut from oxygen displacement (inert gas use), fires, explosions, and toxic exposures to the physical hazards of high pressurization. So in this issue, the Safety Guys offer some tips on accident prevention and safe use of compressed gas cylinders.
Know what you are dealing with
Most workers in laboratory settings are familiar with the physical hazards of dealing with high-pressure, heavy, metal cylinders that come in all sizes and shapes, from little one-pound lecture bottles to railroad tank car-sized vessels. But too many get cavalier about safe handling of these potential “bombs” and associated hazards. The size most commonly used in research laboratories and facilities is the 100-pound-plus cylinder, referred to as a “K”-sized bottle. They are about eight inches in diameter and 48 inches tall, and can contain a wide array of compressed gases.
The requirements for manufacture of cylinders are detailed in Title 49 Code of Federal Regulations, Part 178, Specifications for Packaging, referenced below for those who like to get into the details.2 But for our purpose, we just want to point out the important markings that all cylinders should have permanently stamped on the shoulder. These should show the Department of Transportation specification, the proper service pressure (in gauge pounds per square inch), the manufacturer’s symbol and serial number, the owner’s symbol, and, most important for safety, the date of the initial qualification test and any subsequent tests. Cylinders need to be retested every five years of service. In addition to the permanent markings, the cylinder should also have an identifying label on the shoulder indicating the cylinder’s contents.
Safe handling of cylinders from acceptance to zero (gas left)
The Compressed Gas Association publishes an excellent reference3 as well as a large number of pamphlets on specific gases with detailed information. We will not attempt to cover all the different classes of compressed gases, as that is beyond the scope of this article. What follows are recommended, condensed, general safe-handling rules. We strongly encourage anyone who handles cylinders regularly to become very familiar with these.
Develop written safe-handling procedures
- Develop specific safe-handling and use procedures for your compressed gas cylinders.
Depending on the specific gas used, safety procedures can become quite complex. For example, extremely hazardous gases may require dedicated ventilated storage cabinets, safety interlocks, and elaborate alarm systems. Consult experts for assistance, if necessary.
When accepting full cylinders
- Before accepting or receiving compressed gas cylinders, perform a quick inspection.
- All cylinders should be shipped with regulators removed and safety caps in place.
- Check cylinders for heavy rust or pitting and refuse any questionable ones.
- Check the certification date(s).
- Finally, make sure all cylinders have a durable label that cannot be easily removed and that clearly identifies the contents.
When moving cylinders
- Transport compressed gas cylinders with care.
Since vendors usually move cylinders from the supply truck to our storage area, we need to focus on moving them from the storage room directly to the laboratory. Please do not perform this haphazardly or with a cavalier attitude.
- When transporting, ensure all cylinders are properly secured. Compressed gas cylinders should be transported only using wheeled carts designed for this purpose.
- Make sure safety caps are in place and cylinders are secured to the cart. Common methods include chains, straps, and specialty clamps.
- When moving multiple cylinders do not allow them to bang against or strike each other.
- Finally, become familiar with the route you will travel and be sure to remove all potential obstacles. If lift gates or ramps are used, enlist a spotter or helper before moving cylinders.
When using cylinders
- Double-check the contents to ensure the material is what you think it is and what the label says it is.
- Ensure all cylinders are secured in the work area before making connections. Common methods include chains, straps, and specialty clamps.
- Install a proper regulator when in use, and when not in use remove the regulator and install safety caps.
- Maintain adequate ventilation and temperature control for the use area.
- Finally, close the valve and purge or release the pressure in the system as appropriate and follow your written standard operating procedures at the end of each use.
- Designate a dedicated area for compressed gas cylinder storage, particularly in large facilities and those with high-volume use.
- Segregate cylinders according to fire codes and compatibility. It is important to store by compatibility with proper separation between hazard classes. Be sure to check local fire codes, which specify distances and quantities allowed.
- Secure cylinders to prevent tipping, falling, and knocking together.
- Ensure regulators are removed and safety caps are installed.
- Maintain good ventilation and temperature control.
- Lock and secure the area against theft and vandalism.
- Locate the cylinder storage area away from emergency exits.
- Finally, clearly mark all empty cylinders and segregate these from full cylinders. Empty cylinders should be moved and handled with the same care as full ones and returned to the vendor promptly.
Taking the time to develop and implement a compressed gas safety program for your laboratory research or production facility is paramount in preventing accidents and potential tragedy. Doing this correctly is low cost and easily installed and maintained. Compared with the costs associated with the alternatives it is hard to argue against a good compressed gas safety program.
1. “Lab Safety Gas Cylinders Incidents.” American Industrial Hygiene Association. Falls Church, Virginia. 2016. https://www.aiha.org/get-involved/VolunteerGroups/LabHSCommittee/Incident%20Pages/Lab-Safety-Gas-Cyclinders-Incidents.aspx
2. Title 49 CFR Part 178, Specifications for Packaging. U.S. Department of Transportation. January 2005. http://www.access.gpo.gov/nara/cfr/waisidx_04/49cfr178_04.html.
3. Handbook of Compressed Gases, Compressed Gas Association, Arlington, Virginia. Van Nostrand Reinhold, New York latest edition.
Prudent Practices in the Laboratory, National Research Council. National Academy Press, Washington, D.C., latest edition.
“How Do I Work Safely with Compressed Gases?” Canadian Centre for Occupational Health and Safety. July 2008. http://www.ccohs.ca/oshanswers/prevention/comp_gas.html