Abstract: At 8:30 a.m. on May 21, 2021, an employee working as a heavy equipment operator for a solid waste contractor was leveling the ground with a backhoe at a landfill. The employee was sealing an aluminum deposit from two to three years prior. The aluminum reacted with moisture in the ground releasing ammonia as the operator began to level the ground. It could not be determined if the ammonia overpowered the capabilities of the cartridge respirator or if the respirator failed due to a broken seal or other reason. When the employee detected the ammonia, he left the backhoe ran into the wind. The employee collapsed on the ground and coworkers helped him to fresh air. A coworker who is also the employee's son drove him to the hospital. The process is not routine since the aluminum was buried above grade which has not been the case in over 5 years. It was not possible to recreate the exposure. The employee was hospitalized with scarring on his lung that has improved and he is expected to make a full recovery.