On February 23, 1997, a backup solid-fuel oxygen canister caught fire in the Kvant-1 module. The fire spewed molten metal, and the crew was concerned that it could melt through the hull of the space station. Smoke filled the station, and the crew donned respirators to continue breathing, although some respirators were faulty and did not supply oxygen. After burning for fourteen minutes and using up three fire extinguishers, the fire died out. The smoke remained thick for forty-five minutes after the fire was extinguished. After the respirators ran out of oxygen and the smoke began to clear the crew switched to using filter masks.