Inerting refers to the process of introducing an inert gas into a confined space to displace an already-present gas that poses some sort of hazard.
This process may be used to displace toxic gases, but it is most commonly used to displace oxygen or to reduce the concentration of oxygen within a space if displacement is not possible due to a space being fully enclosed.
Safeopedia Explains Inerting
Inerting is commonly used to prevent unwanted combustion from occurring; for instance, the use of an inerting system is often used by commercial airlines to meet the U.S. Federal Aviation Administration’s Fuel Tank Flammability Reduction rule. In addition to being used to prevent the unwanted combustion of fuel tanks, inerting systems are also used to prevent combustion in the chemical and petrochemical process industries.
Inert gases are chosen to displace unwanted gases because they do not readily react with other chemicals and thus pose no reactivity hazard. The most common methods of inerting are referred to as “purging” methods, and they work by using the inerting gas to force another substance from a particular space. In addition to preventing unwanted combustion as an ongoing safety control, inerting systems can also be used as emergency explosion suppressants in the event that a safety failure creates an incident with an imminent risk of explosion.
The most common inerting gas is nitrogen. Nitrogen is not technically an inert gas but only reacts under a limited range of circumstances, and it is more cost-effective than other gases. Carbon dioxide is also a common inerting gas, and it can be used instead of nitrogen when a gas that is heavier than air is required. However, as carbon dioxide is corrosive in the presence of moisture and reacts more readily than nitrogen, there are a number of situations where its use is not appropriate.
Noble gases are more expensive than nitrogen or carbon dioxide but are also fully inert, and they may be used in specific instances where their properties provide a necessary additional advantage. For example, argon is used as an inerting gas for the purpose of preventing aluminum dust explosions. In the shipping industry, a ship's exhaust gases are often used for inerting purposes.
While inerting is used to reduce occupational risks associated with combustive or toxic gases, inerting gases themselves also pose an occupational hazard. Because the purpose of an inert gas is to displace the presence of oxygen within a space, inadvertent exposure to inert gases may cause fatal asphyxiation. Some inerting gases, such as carbon dioxide, also have a toxic effect. Because of the asphyxiation risks, OSHA classifies the atmosphere produced by inerting processes as being “IDLH,” or “immediately dangerous to life or health.” Major occupational safety standards that are relevant to the use of inerting in most jurisdictions include confined-space standards, as well as standards related to the control and handling of hazardous substances.