Confined Space Gas Limits: The Importance of Gas Monitoring in Confined Spaces Pt. 2

Confined Space Gas Limits: The Importance of Gas Monitoring in Confined Spaces Pt. 2

The second in a two-part series on confined space gas monitoring:

They say that knowledge is power. This is certainly the case when it comes to safety in confined spaces. It is only after we are aware of the potential dangers of confined spaces that we can recognize a seemingly empty space as containing life-threatening possibilities.

BW Honeywell GasAlert Micro Clip XL 4-Gas Monitor

In the first part of our Gas Monitoring discussion, we talked about Oxygen (O2) levels and Lower Explosive Limits (LELs) and how to monitor for them with your gas monitor. In this section, we’ll discuss the other two gases OSHA requires all confined space entrants to test for before entering – Hydrogen Sulfide (H2S) and Carbon Monoxide (CO).

Hydrogen sulfide, the gas that smells like rotten eggs, occurs naturally in hot springs, natural gas and in crude petroleum. It also is produced by the breakdown of organic materials. H2S is heavier than air, so be sure to check all levels of your tank or space before entry.

Because of the distinctive smell of H2S, many workers think they can detect it without proper monitoring equipment. Rely on your monitor, not your sense of smell to detect H2S. With constant low-level exposure, or at a higher concentration, a worker’s ability to smell Hydrogen Sulfide will diminish even though the gas is still present.

Carbon monoxide (CO) is very common on job sites. It is produced from internal combustion engines - pumps, cars and trucks, or generators. A worker who breathes large amounts of CO displaces oxygen in their system. This can result in damage to the heart, brain and other important organs.

The OSHA permissible exposure limit (PEL) for CO is 50 parts per million (ppm). This means that over an 8-hour period a worker should not be exposed to more than 50 ppm. Your monitor will keep track of the total exposure over time as well as exaggerated short term exposure. All you have to do is keep track of your monitor.

For all the hazards of confined space atmospheres, proper monitoring will provide a roadmap for safe entry. Knowing what you are monitoring for and how it is produced will give you an added measure of protection when confined space entry is required.

For more information on confined space entry, gas monitors, and OSHA standards compliance, please contact the confined space experts at

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Feb 27th 2015 Administrator

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