But when it evaporates, the resulting nitrogen gas can fill a much larger space and can rapidly displace air and the oxygen essential to life, leading to an asphyxiation hazard, said Rick L. Danheiser, a professor of chemistry at the Massachusetts Institute of Technology. Because of its low temperature, liquid nitrogen also can cause cryogenic burns on contact, he said.
In poultry and meat plants, the seals on pressurized liquid nitrogen lines must be checked routinely for leaks, union officials said.
If it turns out that the plant was cutting corners to save costs, the company should be prosecuted, said Mark Lauritsen, the director of food processing, packing and manufacturing at the United Food and Commercial Workers International Union, which represents about 250,000 meat and poultry workers.
“This should never ever, ever happen,” given how dangerous the chemical is, Mr. Lauritsen said.
The nitrogen leak was one of several deadly industrial accidents in recent years.
In April 2010, 11 people died when an explosion ripped through the Deepwater Horizon drilling rig in the Gulf of Mexico, unleashing one of the worst offshore oil spills in the United States. In May 2020, 11 people in India died and hundreds were sickened after a tank containing styrene, a liquid used in making plastics, leaked, officials said.
Other recent industrial accidents have sent thousands fleeing from their homes.
In November 2019, 30,000 people in southeast Texas were evacuated after a pair of explosions rocked the Texas Petroleum Chemical plant. And in 2017, 21 emergency workers in Texas were treated for smoke exposure after Hurricane Harvey caused fires at the Arkema chemical plant.
The deadly accident on Thursday morning was silent, at least to one employee, Maria Bonilla, 60.
Ms. Bonilla, a Salvadoran immigrant who does not speak English, was working in the marinating department of the sprawling plant. She did not hear an explosion, or a crash or screams.