Final answer:
Displacing the atmosphere in a permit space with a noncombustible gas renders the environment noncombustible, reducing the risk of fire or explosion by preventing combustion in confined or sensitive areas.
Step-by-step explanation:
Displacing the atmosphere in a permit space by a noncombustible gas to such an extent that the resulting atmosphere is noncombustible effectively makes it noncombustible. This safety procedure is used to prevent fires or explosions by ensuring that the concentration of combustible gases or dust in the air is reduced to a level where combustion cannot occur. In practical terms, this process involves the introduction of a gas like nitrogen or carbon dioxide to displace the oxygen in the space, reducing the risk of flammable materials igniting in environments such as confined spaces, tanks, or silos. These measures are critical when working in environments where the control of combustible materials is necessary for safety.