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Confined Spaces (Internal Link)

A confined space is an area with a small opening that is large enough for someone to enter, and work. See Figure 1. The size and shape of the space can make it hard to move around or work in for a long time. Examples of confined spaces include:


Confines Spaces
Figure 1
  • manholes 

  • tunnels 

  • sewers and sewer silos 

  • sewage digesters 

  • utility vaults 

  • pumping stations 

  • storage tanks and 

  • pits, vats and process vessels 



Hazards of confined spaces

The air can be unsafe (hazardous atmosphere) for a number or reasons.

  • Not enough oxygen: air that has less than 19.5 percent oxygen is dangerous. Without enough oxygen, workers will die because they will not be able to breathe. 

  • Too much oxygen: air that has more than 23.5 percent oxygen increases firehazards. 

  • Flammable gases (gases that will ignite): Methane is the most common flammable gas in sewers. Methane is formed when materials decompose. 

  • Toxic gases and vapors can kill when levels are high. Hydrogen sulfide smells like rotten eggs and sinks to the bottom of the space. Carbon monoxide is a deadly gas that you cannot smell. 

Other hazards of confined space work include:

  • falling objects 

  • very hot or cold temperatures 

  • collapsing sand, grain or other material 

  • loud noises 

  • slips and falls because of wet surfaces 

Protecting workers from the hazards of confined spaces

The following actions are needed to protect workers from the hazards that can be present in confined spaces:

1. Train workers and supervisors about the hazards of confined spaces and how to protect workers.

2. Fill out an entry permit.

Permits should be filled out before a worker enters a confined space and should contain the following information:

  • the location of the space, when it will be entered and for what purpose; 

  • the supervisor in charge; 

  • the person outside of the space (attendant) who is to let the workers know if they must evacuate 

  • the space or who can call for help in an emergency; 

  • test results for dangers in the air; 

  • hazards in the space and how they will be controlled; and 

  • emergency and rescue services that can be called. 

3. Test the air for hazards BEFORE ENTERING!


The device used to measure the air, the monitor, should be operated from outside the confined space. See Figure 2. The area must first be tested for oxygen. The air must have between 19.5 and 23.5 percent oxygen.
The monitor should be able to reach the lowest point in the space. Some gases, like hydrogen sulfide, are heavier than air and sink to the bottom. Other gases, like methane, are lighter than air and rise to the top. Samples need to be taken from the bottom, middle and top levels. 
Monitoring a Manhole
Figure 2


4. Ventilate the area BEFORE ENTERING!

Ventilation is needed if the monitor shows there is not enough oxygen or if it contains toxic gases. Air that is safe to breathe is forced into the confined space. The air must be monitored again to make sure the ventilation has gotten rid of the hazards in the air.

5. Use the right protective equipment.

The type of protective equipment needed depends on the hazards that are present. Equipment that is commonly used for confined space work includes:

  • an air-supplied respirator (see Chapter 4) when there is too little oxygen or toxic gases; 

  • a full body or chest harness and a lifeline to make a rescue; 

  • hard hats, safety goggles, face shields, gloves, disposable suits and ear protection. A non-sparking flashlight may also be needed. 


   6. Be ready to make a rescue WITHOUT HAVING TO ENTER THE AREA! 
Rescue Equipment
Figure 3

Too often, workers die in confined spaces while trying to rescue a co-worker. Employees must be trained in rescue procedures. Be prepared to make a “non-entry” rescue in case of an emergency. A rescue can be made without having to enter the space by using tripods, winches and other types of retrieval systems. See Figure 3.

The attendant may not enter the space to make a rescue until another attendant has arrived on the scene! 


Laws to protect workers in confined spaces

The Occupational Safety and Health Administration (OSHA) regulation to protect workers from the hazards of working in confined spaces is 29 CFR 1910.146. The rule requires the employer to:

  • assign a trained supervisor to make sure that entry into the space and the work is done safely; 

  • determine whether there is a danger in the space from a hazardous atmosphere, being trapped, or other serious hazard BEFORE ANY WORKER ENTERS THE CONFINED SPACE; 

  • have employees who will work in the confined space fill out entry permits; 

  • prevent entry into the area by employees who are not supposed to go into the space; 

  • test the air for hazards before entering and while working in the confined space; 

  • supply air to ventilate the space; 

  • provide protective equipment to the workers; 

  • have an attendant outside the space at all the times someone is working in the confined space; 

  • have equipment set up and ready to make a rescue without having to enter the space; 

  • have emergency plans in place; and 

  • make sure all employees are properly trained to perform their assigned duties.

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