Compressed Gas Cylinder Safety Basics
Liquid nitrogen is used in many laboratory operations, especially in medical, health care, and related facilities.
A couple of recent tragedies involving compressed gas cylinders captured our attention. In the first, employees were performing a swap of nitrogen-supplying equipment. Liquid nitrogen is used in many laboratory operations, especially in medical, health care, and related facilities. In this case, technicians were operating valves and swapping hoses to switch from the nitrogen manifold that was in service to another system. At the time of the incident, nitrogen was being transferred through the manifold when the portable manifold used to transfer the nitrogen ruptured and came apart, striking workers in the area and causing severe injuries. One employee was killed by blunt force trauma to the face and body, with multiple lacerations and broken bones. Eight other employees were also injured.1
The second horrendous accident also involved a cylinder pressure manifold. A worker was filling a 60-cylinder manifold system of compressed oxygen operating at 2,350 lbs of pressure. During filling, a gas cylinder ruptured. At the time of the cylinder rupture, the worker was turning off the cylinder valves. EMS responded to the scene; the worker was transported to Wayne Memorial Hospital and then airlifted to Pitt Memorial Hospital, where he was hospitalized. Because of the severity of the worker’s injury, medical personnel had to amputate both legs at the mid-thigh level.2
The cause of the first accident was most likely over-pressurization of the portable manifold, leading to its failure. In the second incident, the cylinder was either compromised or perhaps over-pressurized. Both incidents may have been avoided by following basic cylinder lab safety rules. Therefore, the Safety Guys thought it would be a good time to review the use and storage of compressed gases in the lab.
We think most would agree that compressed gas use in laboratory research facilities is quite common. These range from inert gases like nitrogen, carbon dioxide, and argon to the highly flammable hydrogen, acetylene, and oxygen to the specialty gases like isoflurane and halothane used for anesthesia. Therefore, we present some basic tips on the safe use of compressed gas cylinders.
Check your cylinders
Compressed gas is contained, transported, stored, and used from heavy-walled metal cylinders. The first step in safe handling of compressed gas cylinders is to understand and check the permanent stamped markings on the shoulder. The requirements for the manufacture of cylinders are detailed in Title 49 Code of Federal Regulations, Part 178, Specifications for Packaging.3 These should show the DOT 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 dates 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 cylinder handling basic rules
Below is an abbreviated set of basic guidelines applicable to all gas cylinders. We want to encourage you to develop and implement a comprehensive, written safety plan for handling and using compressed gas cylinders. The Compressed Gas Association publishes an excellent reference4 as well as many guides on specific gases with more detailed information. There are also specific lab safety symbols and signs for compressed gases that should be prominent in your lab. An attempt to cover all the different classes and types of compressed gases is beyond the scope of this article.
- Check all compressed gas cylinders before accepting or receiving from your vendor. 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.
- Take care transporting compressed gas cylinders. Even though most of us only move cylinders from the vendor supply truck to our storage area or directly to the laboratory, this step is often done haphazardly or with a cavalier attitude. Compressed gas cylinders should be transported using only wheeled carts specifically 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, inspect 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.
- 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. Prior to use, ensure 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 a safety cap. 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.
- Pay attention to storage areas. We would hope that most sites have a designated area for compressed gas cylinder storage, particularly large facilities and those with high-volume use. However, cylinder storage is often relegated to the back closet and overlooked. General safety considerations (mentioned above) include 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, secure and lock the area to protect against theft and vandalism. Preferably, locate the cylinder storage area away from emergency exits. Another important issue is to store by compatibility along with proper separation between hazard classes. 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.
Summary
Great strides in preventing accidents and potential tragedy are made by taking the time to develop and implement a compressed gas safety program. In most cases, proper safe handling is low cost and easily installed and implemented. It is hard to deny that a good compressed gas safety program pays dividends, especially when compared to the costs associated with the alternative.
References:
1. Accident Report Detail: Accident 46526.015. Occupational Safety and Health Administration, US Department of Labor, Washington, DC. June 2013. https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=46526.015
2. Accident Report Detail: Accident 200358174. Occupational Safety and Health Administration, US Department of Labor, Washington, DC. September 2009. https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=200358174
3. 49 CFR Part 178, Specifications for Packaging. US Department of Transportation, January 2005. http://www.access.gpo.gov/nara/cfr/waisidx_04/49cfr178_04.html
4. Handbook of Compressed Gases., Compressed Gas Association, Arlington, VA. Van Nostrand Reinhold, NY, latest edition.