An explosion rocked Schweitzer Hall, which houses chemistry and biochemistry labs, on the Missouri University campus a few short months ago, injuring four students and lab technicians.1 It could have been much worse. It is suspected that combustion of stray gases being used in an experiment, hydrogen being the prominent one of interest, led to the blast. The cause is still being investigated at the time of this writing, but we thought it would be a good time for reviewing our use and storage of compressed gases in the lab.
Laboratory research facilities use a wide variety of compressed gases. These can range from the classic inert gases such as nitrogen, carbon dioxide and argon to the highly flammable hydrogen, involved in the accident above, to acetylene and oxygen used for welding to the specialty gases such as isoflurane and halothane used for anesthesia. So in this issue, the Safety Guys offer a few basic tips on safe use of compressed gas cylinders and preventing accidents and close calls.
How do you know what you are dealing with?
Compressed gas is loaded into, transported in and used from heavy-walled metal cylinders. These cylinders come in all sizes and shapes from little one-pound lecture bottles to railroad tank cars. The size most commonly used in research laboratories and facilities is the eighty-pound cylinders, referred to as “K” size bottles. 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.2 For our purpose, we just want to point out that all cylinders should have permanent stamped markings on the shoulder. These should show the DOT specification; the proper service pressure (in gauge pounds per square inch, psig); the manufacturer’s symbol and serial number; the owner’s symbol; and, most important for safety, the date(s) 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.
Basic rules for safe handling of cylinders from acceptance to zero (gas left)
What follows here is a condensed set of basic guidelines applicable to all gas cylinders. The Compressed Gas Association publishes an excellent reference3 as well as a large number of pamphlets on specific gases with more detailed information. An attempt to cover all the different classes of compressed gases is beyond the scope of this article, but we will gladly respond to readers’ special concerns, perhaps with follow-up articles if interest is high.
Step 1: 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 each cylinder has a durable label that cannot be easily removed and that clearly identifies the contents.
Step 2: Transport compressed gas cylinders with care.
Since we are moving cylinders only from the vendor supply truck to our storage area or directly to the laboratory or facility use area, this step is straightforward but often done haphazardly or with a cavalier attitude. Compressed gas cylinders should be transported using only wheeled carts designed for this purpose. Make sure safety caps are in place and cylinders are secured to the cart. When moving multiple cylinders, do not allow them to bear against or strike each other. Finally, know the route you will travel and remove all potential obstacles. If lift gates or ramps are used, enlist a spotter or helper before moving cylinders.
Step 3: 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. Here are a few basic ground rules to follow. When transporting, ensure all cylinders are properly secured. 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 area. Finally, close the valve and release the pressure in the system at the end of each use.
Step 4: Don’t forget about storage areas.
Most sites have a designated area for compressed gas cylinder storage, particularly large facilities and those with high-volume use. These areas are often relegated to the back closet and overlooked. General safety considerations include many already mentioned above, such as securing cylinders to prevent tipping, falling and knocking together; having regulators removed and safety caps installed; and maintaining good ventilation and temperature control. There are a few important additions, however. First, the area should be locked and secured against theft and vandalism. Preferably, the cylinder storage area should be located away from emergency exits. The next most important issue is storage by compatibility, along with proper separation between hazard classes. Be sure to check local fire codes, which specify distances and quantities allowed. Clearly mark all empty cylinders and segregate these from full cylinders as well. 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 research or production facility will go a long way toward preventing accidents and potential tragedy. Most fixes and corrections are low cost and easily installed and maintained. Compared to the costs associated with the alternatives, it is hard to argue against a good compressed gas safety program.
- Explosion at MU Chemistry Lab Reportedly Injures Four. Williams, Mara Rose. Kansas City Star. June 28, 2010. http:// www.kansascity.com/2010/06/28/2050123_explosionat-mu-chemistry-lab.html?storylink=omni_popular
- 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
- Handbook of Compressed Gases, Compressed Gas Association, Arlington, VA. Van Nostrand Reinhold, NY. Latest edition.
Prudent Practices in the Laboratory, National Research Council. National Academy Press, Washington, D.C. Latest edition.
Compressed Gas Safety page. Canadian Centre for Occupational Health and Safety. July 2008. http://www.ccohs.ca/oshanswers/prevention/comp_gas.html