Abstract: At 3:00 a.m. on July 27, 2022, an employee was bolting a flow meter on a hydrogen cyanide (HCN) line that was dripping fluid with a coworker. The employee stepped away from the job after having difficulty installing the final bolts. The employee waved his hand in front of his face and backed away from the job while removing his fresh air supply. The employee stumbled about twenty feet and collapsed. Coworkers rushed over to the employee to check to see what was wrong with him. Coworkers began removing parts of his chemical protective suit and his chemical boots and began to pour water on him. The employee's eyes rolled to the back of his head and he began to seize while taking shallow rapid breaths. The coworkers called for a man-down signal to dispatch with possible heat exhaustion over the radio. The emergency response team (ERT) responded to the employee's location, initiated CPR, and oxygen was placed on him. The ERT requested for ambulance transport to the plant main gate. While waiting for the ambulance, ERT members asked coworkers at the scene if there was any possibility that the employee was exposed to HCN. The ERT determined that the employee did not meet the criteria for receiving hydroxocobalamin and continued supplying oxygen. During transport to the hospital, the employee received one ampule of amyl nitrite (which is not an antidote for HCN poisoning) as a precaution if he had been exposed to HCN while in the ambulance. At the hospital, the employee received the HCN antidotes but died on July 31, 2022, due to HCN poisoning.