A nitrogen leak at Mississippi Welders Supply on the 600 block of George Street caused the La Crosse Fire Department to evacuate homes in the area Thursday morning.
The call came in to the La Crosse Fire Department around 6 a.m. after someone heard a pop and saw a vapor cloud coming from Mississippi Welders Supply.
The concern was that liquid oxygen had been released into the air. The business and nearby homes were evacuated while authorities investigated.
John Tomten, manager of the cryogenics division of Mississippi Welders Supply, said there were two large tanks next to each other. One was liquid nitrogen; one was liquid oxygen.
Thomten said both of those tanks had a “dual safety release device.” If one of those fails, which in this case happened, someone has to go to the nitrogen tank and turn it off, which switches to the emergency valve. Firefighters had to do this.
In the pressurized tank, the nitrogen is a compressed liquefied gas. Once that hits the oxygen in the air, it turns it immediately to a gas form. Thomten said the hissing sound that people in the area heard was liquid nitrogen trying to leak out of the tank turned into gas and hiss.
Firefighters say they were able to stop the leak on the tank within about half an hour. Then they checked the area with meters to determine it was safe.
The leak was outside the building and no one was in any danger because the gas dissipated as soon as it was released, Thomten said. No liquid spilled and there was no cleanup. The valve that malfunctioned was replaced.
The La Crosse Municipal Transit Utility (MTU) helped displaced residents until authorities determined the area was safe. People were allowed back into the business and their homes just before 7 a.m.
The La Crosse Police Department and Tri-State Ambulance also assisted firefighters during the evacuation.