Common Toxic Substances

Hydrogen sulfide (H₂S) is one of the more common toxic gases found in confined spaces. It is dangerous because:

• It impairs your body's ability to breathe, yet it often cannot be smelled or detected in a space.
• It is highly flammable.
• It is heavier than normal air and can collect in a layer at the bottom of a confined space.
• Breathing it in high concentrations can cause immediate collapse and death.

Hydrogen sulfide can come from raw sewage, crude oil, tanneries, or the pulp and paper industry.

Another toxic gas commonly found in confined spaces is carbon monoxide. Carbon monoxide is dangerous because:

• It is colorless and odorless.
• It reduces the ability of your blood to carry oxygen.
• Breathing it in high concentrations can cause collapse and death.

Carbon monoxide is found in the exhaust fumes of gasoline- and diesel-powered machines; therefore, it is common in the industrial workplace.

Methane (CH₄) is highly explosive. It can leak from a gas line and is a by-product of sewage. It is also found in coal mines. Because methane displaces oxygen, it can smother workers.

To learn more about Firefighter Confined Space visit our Firefighter Confined Space Entry & Rescue Online Training web page.