Last January 28, workers at the Gainesville, Georgia, chicken-packing plant operated by Foundation Foods began to show up for work. Several workers were assigned positions in the below-ground-level freezing room on Production Line 4, one of several in the large plant. Not too long before, the old ammonia-refrigerant freezing system had been replaced with a new liquid-nitrogen (LN2) system.

On the face of it, liquid nitrogen is a safer chemical than ammonia, which is both toxic and explosive. Nitrogen makes up 78 percent of the atmosphere, and while liquid nitrogen can cause painful burns, as long as it is confined to locations inaccessible to workers, no direct harm from it can result. However, breathing nitrogen gas cannot support life.

The freezing stage itself was in a separate freezing room and consisted of an immersion freezing line in which the chicken pieces were immersed in liquid nitrogen at around -321 F, followed by a spiral freezing chamber where the gaseous nitrogen boiling away from the liquid surrounded the pieces as they spiralled upward on a conveyor belt.

Just after the shift started, Line 4 had a problem, and three maintenance workers entered the freezing room. What they apparently didn’t know was that the malfunction had filled the entire room with evaporated liquid nitrogen, displacing most of the oxygen in the room. The workers immediately passed out and died shortly thereafter. Two more workers entered the room and died, and a sixth was sufficiently overcome that he died on the way to the hospital. The release of liquid nitrogen created a condensation fog that made escape difficult, and at least twelve other workers were injured enough to require hospital care.

Both the US Chemical Safety Board (CSB) and the Occupational Health and Safety Administration (OSHA) began investigations of the accident. In February, the CCB issued some preliminary updates, and on July 23, OSHA announced its intention to assess Foundation Food Group Inc.(the plant operator), Messer LLC (the LN2 supplier), Packers Sanitation Services Inc (the cleaning and sanitation service provider) and FS Group Inc (the equipment and mechanical servicing provider) a total of nearly $1 million in fines.

OSHA found that 26 violations had been committed by Foundation Food Group. The agency discovered that the workers at the plant had received no training or warnings about the hazards of LN2 and safety precautions they should observe. There were no written lockout procedures dealing with how maintenance should be performed. While the following is reading between the lines, something like this accident could have occurred if someone had shut off the LN2 supply to the system while leaving an LN2 valve or joint open in the freezing room, and then someone else came along and opened the shut valve, not knowing it would kill six co-workers.

Lockout procedures are vital for work on hazardous equipment of all kinds, ranging from conveyor belts to high-voltage power systems. If equipment is being worked on, a typical lockout procedure specifies brightly-coloured tags that must be placed on critical controls in a way that will prevent the control from being operated. Evidently, nothing like this was done.

Another standard safety measure is to train everyone who has a reason to work inside a confined space where hazardous gases (such as pure nitrogen) can accumulate. Ideally, an oxygen monitor or some way to indicate a problem with the air inside the room should have been operating, but at least the workers should have been made aware of the possible danger. That way they might not have simply walked into the room to their certain deaths.

If a person strays into an area where there is no oxygen but the air pressure and other conditions seem normal, there is usually no time to react, turn around, or do anything except pass out and drop.

I once saw a dashcam video taken from a state trooper’s car. The trooper had stopped to investigate an accident involving a liquid-ammonia truck. The gas had been released invisibly. You can watch as the trooper walks toward the truck and then falls as if shot through the heart –and eventually dies. Even the miserable coal miners of 19th century England were able to bring a canary into the mine with them to give advance warning of “black-damp”—air without enough oxygen to breathe.

But canaries wouldn’t be allowed by the microbiologists who rule meat-packing plants—too unsanitary.

While there was probably some mechanical malfunction that caused the initial release of nitrogen, the fatalities could have been avoided with better communication among all the parties involved. The factory operators needed to give instructions in their employees’ native language (Spanish) about the hazards of working around LN2.

The LN2 supplier needed to communicate with the factory operators and maintenance workers concerning the delivery and transmission of their product. And the maintenance and supervisory personnel in charge of fixing Line 4 needed much better lockout and safety procedures, which were signally lacking in this tragic case.

Vigilance is perhaps not taught that much in business schools. It sounds like an old-fashioned, rather static virtue, somewhat passé when compared with flashier virtues like competitiveness and enterprise. But clearly, whatever safety procedures and safety officers were in place in the Gainesville plant on January 28 were sadly inadequate to prevent a tragedy that didn’t have to happen.

Not everybody enjoys going around their place of business imagining what could go wrong and how to keep it from happening. But that’s the main job description for those charged with the safety of workers, and it’s a job that looks like a loss on a company’s balance sheet until something like the LN2 accident happens.

Then it’s a lost opportunity, and the beginning of something much worse.

This article has been republished from the Engineering Ethics blog

Karl D. Stephan received the B. S. in Engineering from the California Institute of Technology in 1976. Following a year of graduate study at Cornell, he received the Master of Engineering degree in 1977...