Confined Space Safety: Testing the Atmosphere

Gas Detector
October 03, 2019
By Gina Gould

There are many different aspects and key considerations of confined space work activities.

First, you need to determine whether or not the work area meets OSHA’s definition of a confined space.

OSHA defines a confined space as:

  1. Large enough to enter and perform the assigned work
  2. Not designed for continuous human occupancy
  3. Having a limited or restricted means of entry and/or exit

Next, you need to determine whether or not the space is “permit-required.” OSHA defines this as a space that meets the above criteria, plus one or more of the following:

  1. Contains, or has the potential to contain, a hazardous atmosphere
  2. Contains a material with the potential to engulf someone who enters the space
  3. Has an internal configuration that might cause an entrant to be trapped or asphyxiated by inwardly converging walls or by a floor that slopes downward and tapers to a smaller cross-section
  4. Contains any other recognized serious safety or health hazards

Most of the permit-required criteria are quickly recognizable. But how do you determine if the space “contains or has the potential to contain” a hazardous atmosphere?

The answer is by conducting atmospheric testing.

Testing the Atmosphere

Evaluation tests are performed to determine which chemical hazards may be present while employees are conducting their work. This should be done prior to entering the space.

Once you know which atmospheric hazards you are dealing with, you can identify the necessary steps for protecting your employees.

Even if no atmospheric hazards are identified during the evaluation tests, it’s important to consider the possibility that this could change while the person conducts the work.

For example, chemicals used during repairs or maintenance projects can emit fumes, gases, or vapors that can easily overtake the worker within a confined space. Additionally, welding within a confined space can create hazards associated with sparks and flammability.

This is why it’s a good idea to equip your employees with a personal gas-detection monitor for use in a permit-required space.

There are many different styles of monitors available. Choose one that is able to detect the hazards most likely to be present in the confined spaces at your workplace.

A four-gas monitor is pretty standard for most industries. These monitors are able to detect the following:

  1. Oxygen
  2. Carbon Monoxide
  3. Hydrogen Sulfide
  4. Flammable Gases

Hazardous Gases

Oxygen (O2) can be hazardous both when there is too much and when there is too little.

When there’s not enough oxygen (below 19.5%), workers can become dizzy or lose consciousness. It can even result in death. When there’s too much oxygen (above 23.5%), the space is at risk for a much more dangerous and faster-burning fire.

Carbon monoxide (CO) is poisonous when excess levels are inhaled. It’s a colorless, odorless gas and therefore nearly impossible to detect without a proper monitor.

Hydrogen sulfide (H2S) is a colorless, flammable gas that has a distinct “rotten egg” odor. In addition to being flammable, it can also cause irritation in the eyes, nose, throat, and lungs.

Other flammable gases are measured as LELs, or lower explosive limits. LELs are the lowest concentration of gases or vapors capable of producing a fire. It’s especially important to check for these hazards during welding, repairs, or maintenance activities.

Confined Space Safety

Testing the atmosphere for hazardous gases is just one aspect of confined space safety. A well-rounded confined space safety program also includes written procedures, employee training, proper equipment, a sufficient rescue plan, and various other elements.

Author

Gina Gould

Gina Gould