Confined Space

Many workers are injured and killed each year while working in confined spaces. Of those deaths, approximately 60% are individuals who entered a space trying to rescue someone else.

A confined space is defined by its characteristics, it is any space that:

  • Has limited access for entry and exit AND
  • Is not intended for continuous human occupancy AND
  • Is large enough for a person to enter and conduct work

There are two different types of confined space, permit required and non-permit required.

Non-Permit Required

These are confined spaces that do not have the potential to cause serious harm or death as a result of hazards in the space.

The atmosphere in these spaces must be tested BEFORE ENTRY to ensure that conditions have not changed. If the atmospheric conditions change the space will become a Permit Required confined space.

Examples  of non-permit required confined spaces on campus include:

  • Utility Tunnels
  • Crawl Spaces
  • Elevator Pits
  • Air Handling Units

Permit Required

These are confined spaces that have hazards that could cause serious harm or death.

These spaces have one or more of the following characteristics:

  • Contains, or has the potential to contain, a hazardous atmosphere
    • Oxygen below 19.5% or above 23.5%
    • Presence of toxic gases (carbon monoxide & hydrogen sulfide are most common)
    • Presence of combustible gases (methane, gasoline fumes, acetylene…)
  • Contains material that could engulf an entrant
  • Contains obstacles that make entry and exit difficult
  • Contains some other serious safety or health hazard
    • Electrical hazards
    • Mechanical hazards (mixers, crushers…)

Confined Space Workers


Attendants stand outside the confined space and monitor the Entrant’s safety.

The attendant:

  • Monitors entrants during the job and tracks all entry & exit from the space
  • Monitors and records atmospheric conditions in the space before and during work
  • Ensures no one accidentally enters the space
  • Summons emergency response, if needed

The attendant NEVER enters the confined space!


The people going to work in the confined space are the entrants.

The entrant(s) must:

  • Ensure that the space has been adequately ventilated, isolated, emptied, or otherwise made safe for entry
  • Be familiar with the work to be performed and the procedures for working safely
  • Follow all safety rules and procedures for the job/task
  • Use all appropriate PPE
  • Immediately exit the space upon word of the attendant


Supervisors must ensure the safety of their employees.

The supervisor must:

  • Ensure that all personnel are aware of the hazards associated with the space and that safety briefings are attended by all participants
  • Fill out required work permits
  • Ensure rescue services are available before allowing any entry into the space
  • Ensure protection is provided to entrants by verifying that hazards have been removed or adequately addressed
  • Support the attendant’s authority in controlling access to the space
  • Verify that all personnel have exited the space prior to closing

Working in a Confined Space

There are four steps for working in a confined space

1. Test the Atmosphere

If problems are detected with the atmosphere in the confined space, the area will need to be ventilated. No one can enter the space until the atmosphere tests show the space is safe for entry. Ventilation must continue throughout the confined space work.

Before entering any confined space, the air inside the space must be checked using one of the 4-gas meters.

These meters check oxygen, carbon monoxide, and hydrogen sulfide levels, and check for the presence of flammable vapors in the atmosphere.

  • Oxygen: levels must be between 19.5% and 23.5%
  • Carbon monoxide: the permissible exposure level over eight hours is 50 ppm and the ceiling is 200 ppm
  • Hydrogen sulfide: the permissible exposure level over eight hours is 10 ppm
  • Any flammable vapors must be below 10% of the lower explosive limit (LEL) before entry.

2. Work and Hazard Briefing

Everyone involved in the confined space work must attend a briefing on the procedures to be used, the hazards involved, the personal protective equipment required, and the emergency plan.

  • If the space being entered is a Permit-Required confined space, a Confined Space Entry Permit is required. This paperwork must be completed and reviewed during the briefing.

3. Enter Space

Once steps one and two are complete, work in the confined space can start. Before entering the space, personnel should make sure they have their personal protective equipment on.

  • If the confined space requires an entry permit, everyone entering the space must sign in and they must sign out when they leave. The attendant will maintain the sign-in log.

Once inside the space, the personnel should make sure they are able to communicate. If there is an attendant, all entrants should be able to hear that person throughout the work process. If radios are being used for communication they should be checked to make sure they are working and the volume is high enough.

4. Leave the Space

All equipment and personnel must be removed from the space when work is completed.

  • If the confined space requires an entry permit, the supervisor is responsible for ensuring everyone and everything is out of the space before it is closed. Once everyone is out, the permit should be filed in Rozell.

The job should be reviewed once complete. Any problems that came up during the job should be noted and ways to fix the issues should be discussed. Problems and potential solutions can be stored with the permit paperwork in Rozell, if applicable.

Hot Work

All hot work (e.g., welding, cutting, brazing) done in confined spaces require a Hot Work Permit in addition to the Confined Space Entry Permit.

Special precautions must be taken before and during hot work.

  • All combustible materials in the confined space must be removed before work
  • A fire extinguisher must be available at the site
  • Local exhaust ventilation is required, and must be strong enough to remove atmospheric contamination resulting from the hot work
  • Respirator protection may be required if ventilation is not able to remove enough contaminants to allow for safe working conditions
  • Air monitoring will be necessary throughout the procedure to ensure worker safety

Confined Space Safety

There are several important safety considerations when working in a confined space.

Atmospheric Stratification

Air within a confined space can form layers based on the density of different chemicals present. This stratification has the potential to cause two different problems within a confined space:

  • If atmospheric testing isn’t done at multiple heights within the confined space, hazardous conditions may be missed.
  • When walking through the space the air will mix; air that was safe initially can become hazardous as it combines with unsafe layers.

Thermometer reading cold temperature with snowflake behind it and thermometer reading hot temperature with a sun behind it

Extreme Environmental Conditions

Environmental conditions can be amplified within a confined space.   Confined spaces can become extremely hot or cold and may have very high humidity. Workers within a confined space should take care to ensure they are not affected by the environment they are exposed to, and attendants should be alert for heat and cold related illness symptoms in the entrants.

Workers in hot confined spaces should follow the guidelines in the Outdoor Heat Exposure program.


Low light levels within a confined space can make navigating even more confusing. Employees should be especially careful when moving around confined spaces with low light conditions. Obstacles, ground level changes, and low ceilings or overhead pipes all become more hazardous if you can’t see them very well.

Special protective equipment (e.g., hard hats or headlamps) may be needed in some confined spaces.

Lights being placed in confined spaces that have flammable materials or vapors will need to be intrinsically safe (designed so they do not produce any sparks or much heat).

Respiratory Hazards


If asbestos is loose/friable it has the potential to become airborne when working in a confined space, this is especially true if ventilation is necessary. If the confined space has loose/friable asbestos it will need to be abated by qualified personnel, or the work in the space will need to be completed by qualified personnel using supplied air.

Decaying Material

Spaces that have had water present may have decaying organic matter. This material can produce hazardous gases such as hydrogen sulfide and carbon monoxide. Extra atmospheric monitoring may be necessary in these spaces.


If mold is present in the confined space, workers will require the use of respiratory protection and protective clothing.


Ventilation may be necessary in a confined space if the atmosphere present in the space is not safe or if hot work will produce hazardous vapors. Adequately ventilating a space can be difficult and it may be necessary to partition the working space from a larger area to make ventilating easier and/or for workers to wear respiratory protection along with the ventilation.

The noises from ventilation can make communication between entrants and the attendant more difficult; alternate communication methods may be necessary.

When setting up a ventilation system for confined space work:
  • Make sure air is always being forced into a space, a second pump can be pulling air out but the first pump must always be putting air in
  • Set up the air pump in an area with fresh air away from idling cars, machinery, and the mouth of the confined space
  • Blow air toward where the employees are working
  • Ventilation must continue the entire time workers are inside the space
  • Continuous air monitoring with the 4-gas meters is required whenever ventilation is used in a space

Confined Space Resources