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Inert Gas

By: Tabitha Mishra
| Last updated: September 2, 2021

What Does Inert Gas Mean?

An inert gas is a gas that does not form chemical reactions with other chemical substances and therefore does not form chemical compounds.

Traditionally, the term has been used to describe the seven elements in group 18 of the periodic table:

  • Helium (He)
  • Neon (Ne)
  • Argon (Ar)
  • Krypton (Kr)
  • Xenon (Xe)
  • Radon (Rn)
  • Oganesson (Og)

Safeopedia Explains Inert Gas

The term “inert gas” is somewhat of a misnomer, as these gases can, in fact, be reactive under certain conditions. As such, in the context of chemistry and materials science, these gases are generally referred to as noble gases. The term “noble” has historically been used in chemistry (and prior to that, in alchemy) to describe the reluctance of certain metals to react chemically, and the term “noble gas” is used to connote that same reluctance.

Nitrogen's Status as an Idle Gas

Although it is not technically an inert (or noble) gas, nitrogen is often referred to as an inert gas because it shares the same low reactivity and reluctance to form compounds that noble gases do. Certain gaseous compounds, such as carbon dioxide, are also commonly referred to as inert gases for this reason.

Toxicity and Combustibility

Due to their very low reactivity, inert gases are nontoxic and noncombustible. This makes them preferable to use in many situations in which other gases would be unsafe. They can also be used to prevent or suppress unsafe reactions. For example, inert gas fire suppression systems work by displacing the oxygen that is needed to sustain a fire, which can limit the spread of a fire or even extinguish it altogether. The use of inert gas fire suppression systems is very common in workplaces where electrical fires pose a significant risk.

Workplace Uses of Inert Gases

Inert gases are used in workplaces for a number of purposes. Many of these uses are not focused on safety; however, they are also used as an important safety tool, such as in the fire suppression systems discussed above.

Uses of inert gases that aren’t focused on safety include their use as a compressed gas. Numerous industries use inert compressed gases to operate specific pieces of industrial equipment, such as those that rely on pneumatic tools. While these uses aren’t explicitly safety focused, the use of an inert gas is often preferable, as it eliminates any danger that the gas will react if introduced into a potentially hazardous setting.

The use of compressed inert gases is not 100% safe. The primary danger associated with the use of a compressed inert gas is the danger of the gas tank or cylinder rupturing violently, which could potentially cause it to explode due to the sudden pressure release.

Certain types of welding and chemical process activities also use inert gases as “shields” to prevent unwanted chemical reactions. For example, metal inert gas (MIG) welding is a type of arc welding that uses inert gas as a “shielding gas” to prevent airborne contaminants from affecting the welding process. Argon and helium are the most common gases used for this purpose.

In addition to their use as a fire suppression tool, inert gases are also used in a variety of other safety-promoting contexts. For example, an inert gas system is a vital safety tool on oil tankers. Partially filled and empty oil tanks contain combustible vapors that can act as a major explosion hazard if they mix with sufficient quantities of oxygen. Inert gas systems prevent this by injecting inert gas into the empty part of the tank - this forces regular air out of the tank, removing the oxygen-rich conditions necessary for oil vapors to ignite.

Inerting Confined Spaces

Inert gases are also used to eliminate oxygen from confined spaces, such as certain sewers, that are at risk from combustible gases. This process, called “inerting,” generally involves using inert gases to purge combustible gases from the space. If workers need to operate within the inerted space, the lack of oxygen means they will need to use a supplied air respirator at all times.

The tendency of inert gases to displace oxygen-containing air from confined spaces is the primary danger associated with them. Inert gases are classified as asphyxiants, meaning if they’re used in poorly ventilated spaces, they can cause asphyxiation. It is therefore necessary to closely monitor the oxygen content of any enclosed space in which inert gasses are regularly used in order to prevent employees operating in the area from inadvertently suffocating.

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