Abstract: At 9:00 a.m. on November 8, 2019, an employee working on a farm was performing maintenance and repairs on an Anhydrous Ammonia Farm Field Applicator known as a "toolbar". The employee was hand twisting the tee to separate it from the nipple. The nipple had dual male end threads connecting the tee to the cooler. A coworker (Operator) had bled the toolbar the previous evening due to a leak detected at the nipple. The nipple was located at the back side of the cooler between the cooler to the tee. Under normal operations, ammonia flows from one of two side-by-side 1000-gallon tanks through the hose, strainer, valve, tee, nipple, cooler, manifolds, and then to the knives which inject the chemical into the soil. The next morning, the employee said he verified the system was unpressurized by opening a bleeder. The employee was disconnecting the system hose components and had removed the last component tee leading to the nipple connected to the cooler. The cooler is where approximately 4 gallons of ammonia is stored in the system during normal operations at a pressure of approximately 57 psi. The employee thought the system was empty and unpressurized because the coworker bled the system the previous night. But some liquid ammonia remained in the cooler after the system was bled off. The low temperature for the day was 14 degrees Fahrenheit. The employee hand twisted the tee off the nipple opening a direct air path to the cooler and ammonia vapor burst out of the nipple with a hissing sound for about two seconds and struck the employee's hands and legs. The employee was wearing chemical goggles and 12-inch black rubber gloves, but the ammonia still made skin contact inside the gloves on his wrist and hands and inside his clothing on his legs. The employee sustained severe caustic chemical burns to the hands and legs and was hospitalized.