On Jan. 28, at a Foundation Food Group chicken processing operation in Gainesville, Ga., six workers died and at least 12 people were injured trying to contain a nitrogen leak. Four of the injured were firefighters.
The nitrogen was used as a coolant in a quick-freezing process to prepare chicken parts for restaurants and food service customers. The victims were attempting to troubleshoot the malfunctioning freezer.
In late July, the U.S. Department of Labor held a news conference where it announced that $1 million in fines and 59 citations were leveled against Foundation Food Group, Messer LLC, Packers Sanitation Services and FS Group Inc. Messer installed the freezer and leased it to Foundation. FS Group was fined for not properly training employees on the hazards of liquid nitrogen, according to the Gainesville Times.
“Make no mistake, this was an entirely preventable tragedy,” Labor Secretary Marty Walsh told reporters in an Atlanta news conference.
According to a Reuters’ report, OSHA’s investigation found that the companies failed to implement needed safety protocols to prevent the leak, the workers were not taught about the dangers of nitrogen, and they lacked the training and equipment to save lives.
The companies can challenge OSHA’s penalties within 15 business days, and there are six wrongful death lawsuits under way.
Liquid nitrogen is used in a range of applications from the large industrial operations like this one in Georgia, down to high-end restaurants using it for specialty cocktails and dishes. And the recent rise in popularity of cryotherapy in spas and fitness centers, which often uses liquid nitrogen to chill the body, similar to ice bath immersions, has liquid nitrogen in unexpected places.
As we know, liquid nitrogen is dangerous as it can burn flesh. More importantly, nitrogen displaces oxygen which leads to asphyxiation. It is especially dangerous because, like CO, the body doesn’t recognize the presence of nitrogen until it is too late — there’s no pungent smell, burning to eyes or other early warning signs.
When training or leading firefighters on nitrogen leaks, here are four key factors to keep them safe.
Wear full PPE including SCBA. Having no exposed skin will reduce the risk of frost bite and more serious burns. SCBA is a must as nitrogen displaces oxygen — that means going on air, not just wearing the pack and having the mask dangle around the neck. And as with fires, when working in large facilities like processing plants, firefighters must monitor air consumption to ensure they have enough to make it out of the hazardous environment.
Monitor for oxygen levels. This may be the only indication that nitrogen is present if the tanks are not readily accessible or there is no one on site familiar with the operation. In training evolutions, use a device like HazSim to replicate depleted oxygen and force firefighters to deduce nitrogen may be present.
Ventilate the area. Since nitrogen is inert, it can be safely vented into the atmosphere. Reintroducing outside air will raise the oxygen levels.
Be on the alert for potential explosions. Cryogenic storage containers can hold between 80 and 450 liters at pressures up to 350 psig. They have pressure relief valves and rupture discs to protect against pressure build up. According to Utah State University, pressure and chemical reactions can trigger explosions.
Heat flux will vaporize the liquid and potentially cause pressure buildup in the container and transfer lines. On vaporization, liquid nitrogen expands by a factor of 696; one liter of liquid nitrogen becomes 24.6 cubic feet of nitrogen gas. Cryogenic fluids with a boiling point below that of liquid oxygen can condense oxygen from the atmosphere. Repeated replenishment of the system can thereby cause oxygen to accumulate as an unwanted contaminant. Violent reactions like rapid combustions or explosion may occur if the materials contacting the oxygen are combustible.
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