An ammonia leak at a Tyson Foods plant could have been deadly.

A toxic ammonia leak this week at a Tyson Foods plant in Tennessee was yet another reminder that meatpacking and poultry processing plants are some of the most dangerous workplaces in the nation. In the wee hours of the morning September 5, an overnight crew member discovered a “large ammonia leak” at the Goodlettsville plant, The Tennessean reported. Streets and the interstate surrounding the beef processing plant were shut down, and 20 workers and more than 200 residents in the region were evacuated as firefighters spent nearly four hours stopping the leak. While chemical leaks at plants are not an everyday occurrence, they are usually deadly. In January, six people died when a liquid nitrogen refrigerant line ruptured at Foundation Food Group’s Gainesville, Georgia poultry plant. Earlier this summer, federal workplace safety officials proposed nearly $1 million in fines against the four companies responsible for the “preventable tragedy.”