In my work providing risk management and safety advice regarding gas hazards (mostly flammable), I often speak about the hazards of nitrogen. The January 28 incident that killed six workers at Prime Pak Foods/Foundation Food Group in Gainesville, Ga., reinforces the dangers of not only nitrogen but all asphyxiants.
Nitrogen seems so innocent because it's 78% of every breath we take. It’s hard for people to understand that a little more can kill you with one breath, but this incident reinforces that danger. I’m not sure that nitrogen and asphyxiation hazards in general are given the respect they deserve. I am writing this to reinforce the dangers of gas hazards, to provide you with some training tools for your staff and to give you places to go with the information you need to verify that what you might have or be operating is as safe as you can make it and meets all applicable codes and standards.
I classify gas hazards into four categories:
- Pressure release from the overpressure of a vessel or pipe failing catastrophically.
- Toxicity or poisoning, as from carbon monoxide or hydrogen sulfide.
- Flammability
- Asphyxiation or displacing oxygen.
Additional Resources
The Rules for Compressed Gases
Here are some other places to go for help. The NFPA standard for compressed gases is NFPA 55, (Compressed Gases and Cryogenic Fluids Code). There’s a 2020 edition that is available for viewing for free at www.NFPA.org. The information contained in this document is a must if you own or operate compressed gas or cryogenic systems at your facility. There’s also an organization called the Compressed Gas Association, which is very active in all issues regarding compressed gas safety and has lots of very good information on its website.
Other references
US Chemical Safety Board Videos and information
U.S. Navy Iwo Jima Accident Paper-1990, David Petersen
Make sure that for whatever gas you are using you have MSDS information available and review the hazards related to each category.
Nitrogen is often used for inerting things (purging), heat treating operations and for making things cold. It’s an odorless gas, and unless it’s heated or cooled it’s about the same specific gravity or weight as air. It’s often provided at relatively high pressures and in some cases cryogenically. The high pressure and the cryogenics make for additional hazards.
High pressures and cryogenics imply special piping systems and pressure ratings of connected hoses and fittings, along with a need for periodic leak checks. However, respect for these gases and the things that can go wrong, especially in indoor applications, means that consideration should be given to area oxygen monitoring and alarms along with personal detectors for employees.
Depending on the circumstances, E-stops tied to shut off valves and emergency ventilation systems can be abatement tools. All of these considerations should be evaluated from a classical hierarchy of risk perspective using tools such as process hazard analysis.
It’s not just nitrogen that can immediately become a dangerous asphyxiant. Any inert gas used in a specialized application, especially indoors, is a concern. This could be argon under pressure in welding applications, gases used for chip making and even steam. Steam releases in confined areas can overwhelm those exposed and cook their lungs before they have time to escape. This is why in my safety and risk training programs I advocate for fixing all steam leaks as a priority (especially in high pressure systems).
Simple gasket blowouts between flanges can happen without warning and take lives within seconds if they occur in somewhat confined areas. The Navy suffered such a tragedy with a large steam release in confined areas aboard the USS Iwo Jima in 1990 when 10 sailors died.
I hope that after reading this you have a healthy respect for nitrogen and can consider at least training for your staff if it is in use, even periodic use. There are plenty of materials available at the U.S. Chemical Safety Board website that can help. Make sure that if you use standards like NFPA 56 for purging flammable gas piping systems and you use nitrogen in this process, everyone is aware of what can happen with one breath of nitrogen. Likewise, it’s time right now to review all the other possible asphyxiants, the confined spaces and to get after those steam leaks.
John R. Puskar, P.E. is President of Prescient Technical Services LLC. He is a licensed Mechanical Engineer and has been practicing for over 40 years. His firm has provided safety and risk management programs related to gas hazards and fuel-fired equipment for major manufacturers and utilities throughout the world. Puskar serves on a number of nationally recognized safety standards committees including NFPA 54 (National Fuel Gas Code), NFPA 56 (Flammable Gas Piping Safety), NFPA 85 (Boiler Combustion Hazards), and NFPA 820 (Waste Water Treatment Plant Fire Safety).
