Abstract: At approximately 12:00 p.m. on February 24, 2023, an employee was performing well site pumping operations for an oil and gas producer. A coworker had been trying to contact the employee unsuccessfully, so he went to the oil and gas well site where the employee was working to check on him. The coworker found the employee unresponsive in the small 9-foot by 10-foot well shack. The door had been closed when the coworker arrived. The well site is a known to have hydrogen sulfide present in the air at times. The coworker observed that a hose was attached to a valve on the discharge side of a pump. The pump is used to transfer fluid from a tank that is used to separate natural well gases from fluid (condensate and produced water) prior to the gases going to a flare. The coworker observed an overturned bucket in the shack with a small puddle of fluid at the end of the hose. The employee was using the hose and bucket in an attempt to clear a blockage from the pump. The coworker pulled the employee from the space and summoned emergency response. He conducted CPR while he waited for medical help to arrive. The coworker reported that the employee had foam in his mouth and blood was coming out of the employee's mouth when he performed CPR. The employee also had chemical type burns. The employee was transported to the hospital, where he was pronounced dead. The employee was overcome by high levels of flammable gases, including potential hydrogen sulfide overexposure.