Chapter Corner

Confined Spaces

Posted in: Safety Corner, July 2013

Insights_DangerSign.gifThe electrical trade presents many hazards to the electrical contractor who must at times work on energized equipment, on roofs, or on busy job sites. Being lowered down into vault or walking into some other confined space where work must be performed adds yet another dynamic to the job and other existing hazards that requires special skills. Confined spaces are challenging on many fronts. Let's walk through some things you may want to consider and review available tools that can help in the preparation for work in confined spaces. Identifying and labeling confined spaces, instituting and maintaining onsite emergency response plans, and providing training for workers and supervisors can save lives. Let's explore more on this topic together.

Identifying Confined Spaces

A confined space does not have to only be those locations where you are lowered into a pit or other similar underground vault type of situation; there are many other less obvious examples that meet the OSHA definition of confined spaces. OSHA defines a confined space as a space that:

  • Is large enough and so configured that an employee can bodily enter and perform assigned work

  • Has limited or restricted means for entry or exit

  • Is not designed for continuous employee occupancy.

Many examples exist to help define confined spaces. The work being performed doesn’t just have to be electrical work, confined spaces present themselves to all types of trades. Some obvious examples include tanks, vessels, silos, storage bins, hoppers, vaults and pits. Take a second look at the definition above. There are many other less obvious examples and situations on the job that may meet this definition.

For example, in addition to the above definition, OSHA uses the term "permit-required confined space" (permit space) to describe a confined space that has one or more of the following characteristics:

  • Contains or has the potential to contain a hazardous atmosphere
  • Contains a material that has the potential to engulf an entrant
  • Has walls that converge inward or floors that slope downward and taper into a smaller area which could trap or asphyxiate an entrant
  • Contains any other recognized safety or health hazard, such as unguarded machinery, exposed live wires, or heat stress

The list above provides more criteria that may help expand our understanding of confined spaces. It’s more than just those physically tight spaces we immediately see in our minds eye when we hear the word. A hazardous atmosphere, and the possible engulf of the entrant, seems to move this definition to other less physically constrained locations. Because work in confined spaces may be required / encountered in any type of trade, the first step to preventing fatalities or injuries is to understand these details, evaluate your work area and be able to identify confined space work.

Identifying the Hazards

Being able to identify a confined space is the first task but we must be able to identify the hazards as well to ensure work, if performed at all, is performed safely. Hazards in confined spaces could resemble the hazards we have in regular workspaces except for the fact that they can be even more hazardous in a confined space. The following are just some of the hazards you may consider for your identified confined space. Use this list with your team to spark the thought process that may lead to identifying other hazards as well.

  • Hazardous Atmosphere: when reviewing the confined space, we must consider the very basic concept of air quality. The hazard may present itself due to a lack of natural air movement, presence of dust and other similar particles, heavier gases that displace oxygen, or other similar situations. The space may be oxygen-deficient, flammable and/or toxic. Atmospheric conditions may exist before you enter or can be caused by the work being performed. All possibilities must be considered.

  • Oxygen-Deficient: OSHA defines an oxygen-deficient atmosphere as one that has less than 19.5% available oxygen. Normal atmosphere contains between 20.8 and 21 percent oxygen. Entering an Oxygen-deficient space will require the use of self-contained breathing apparatus (SCBA) equipment. The cause of the Oxygen deficiency could be due to the work being performed such as welding, brazing or other similar work or due to other not so obvious sources; carbon dioxide, nitrogen or other similar gases that displace oxygen. Oxygen can also be consumed by rusting metal, ripening fruits, drying paint or coatings, combustion, or bacterial activities.

  • Flammable Atmospheres: OSHA defines flammable atmospheres as those with a concentration of flammable vapors at or above 10 percent of the lower explosive limit (LEL) when located in confined spaces. However, atmospheres with flammable vapors below 10 percent of the LEL may be too lean to burn but should still be considered not necessarily safe. When a space contains or produces measurable flammable vapors below the 10 percent LEL, it might indicate that flammable vapors are being released or introduced into the space and could present a hazard over time. Oxygen in the air and a flammable gas, vapor, or dust in the proper mixture makes an atmosphere flammable. With the right recipe and introduction of an ignition source, an explosion will result. The ignition source can be a direct flame or a spark from a tool including those generated from electrical tools. An oxygen-enriched atmosphere, those above 21%, will act to assist the burning of flammable materials such as clothes or even hair causing them to burn violently if ignited. Never use pure oxygen to ventilate a confined space.

  • Toxic Atmospheres: An atmosphere can become toxic when the permissible exposure limits for specific types of airborne substances are exceeded. Substances such as liquids, vapors, gases, mists, and dusts are all fair game in this category of hazard. The product may be stored in the space or actively being used during work. The toxicants may not be located in the specified confined space but rather located adjacent to it. Some good references here are OSHA 29 CFR 1910 Subpart G, “Occupational Health and Environmental Control”, Subpart H, “Hazardous Materials”, and Subpart Z, “Toxic and Hazardous Substances”.

  • Physical Hazards

    • Hearing: Decibel levels may increase when in a confined space that does not dissipate or absorb the sound levels that can damage hearing.

    • Moving Parts: When there are physical constraints that may cause you to be near moving parts, entanglement or the many types of physical trauma could result should you come in contact with the moving equipment.

    • Falls: Slipping, sliding, tripping or other causes can result in falls should the confined space place the worker in situations where a fall is possible.

    • Temperature: Whether the extreme temperature is atmospheric or surface related, they can be deadly. High temperatures can result in fluid loss and /or over-exhaustion. Extreme cold temperatures can also result in hazards to the worker from frost bite to hyperthermia.

    • Shifting or Collapse: Depending upon the confined space, surrounding material whether it is grain, boxed or loose product, earthen walls, or any of a list of liquids, could result in burial due to a shift or collapse of your barriers.

    • Visibility: not seeing what you are working on, where your exits are, or where other hazards may be is another possibility when working in confined spaces.

The above should be enough to jog your thought process in identifying the hazards in your specific applications. Not every confined space is considered equal. You must closely review each situation before you or someone else on your team proceeds. Do not assume a confined space is a small space. Remember to consider the atmospheric conditions of your work space.

Planning and Preparation

Each time you or someone on your team plans to enter a work space, someone must determine if that space meets the definition of a confined space. A confined space hazard assessment and control program should be implemented and followed. Before you send a person into a confined space, consider the work that must be conducted and ensure that it must in fact be performed inside the confined space. In many cases where there have been deaths in confined spaces, the work could have been done outside the confined space. The employer must evaluate the workplace to determine if any spaces are permit-required confined spaces. Proper signage must be implemented should the workplace contain permit spaces. If these areas are areas where employees will not enter, additional steps should be taken to prevent entry.

A good way to avoid occurrences of accidents and deaths due to confined space work is to have written procedures and proper training. The employer can go a long way by creating entry procedures for permit-required confined spaces that include the following:

  • Evaluate hazardous conditions and post warning signs at entry.
  • Provide equipment for testing the atmosphere.
  • Document the atmosphere test results. A written entry permit with proper posting of the results outside of the confined space is a good start.
  • Train workers who must enter confined spaces on your documented entry procedures.
  • Implement measures to prevent unauthorized entry.
  • Ensure a safe atmosphere, prior to entry, through implementing such techniques as continuous forced-air ventilation.
  • Maintain a safe atmosphere through continuously monitoring the atmosphere in the confined space.
  • Workers inside should be assisted by attendants outside to maintain communication and implement a rescue plan, if necessary.
  • Never send a working in a confined space without assistance from outside. Never work alone.

One thing we sometimes overlook in our preparation is the planning for if/when things go wrong. When a problem arises, your team must be prepared to respond. Unfortunately, many deaths occur when trying to rescue a worker from a confined space. A good plan for retrieval when evaluating a confined space and the work that is to be performed can lead to an extraction achieved in a safe manner. Although easier said than done, a safe extraction has a much greater chance of success when planned in advance.

The important thing to remember is that each time a worker plans to enter any work space, the worker should determine if that work space is considered a confined space, assess the hazards and plan the work accordingly. The following references could help you create your confined spaces hazard assessment and control program.


  1. Title 29, Code of Federal Regulations, Part 1910.146, “Permit-Required Confined Spaces."
  2. National Fire Protection Association (NFPA), NFPA 101, “Life Safety Code”,
  3. National Fire Protection Association (NFPA), NFPA 70E, “Standard for Electrical Safety in the Workplace”,
  4. Occupational Safety and Health Administration (OSHA), “Confined Spaces”,
  5. Centers for Disease Control (CDC), National Institute for Occupational Safety and Health (NIOSH) “Confined Spaces”,
  6. Centers for Disease Control (CDC), “A Guide to Safety in Confined Spaces”,
  7. Canadian Center for Occupational Health and Safety (CCOHS), “Confined Space – Introduction”,

Closing Remarks

The above is just the tip of the iceberg when it comes to working in confined spaces. It should be enough for a start at developing your confined spaces hazard assessment and control program.

Thomas Domitrovich, P.E. is a National Application Engineer with IEC National Platinum Partner Eaton Corporation in Pittsburgh, PA. He has more than 20 years of experience as an Electrical Engineer and is a LEED Accredited Professional. Thomas is active in various trade organizations on various levels with the Independent Electrical Contractors (IEC), International Association of Electrical Inspectors (IAEI), Institute of Electrical and Electronic Engineers (IEEE), National Electrical Manufacturer’s Association (NEMA) and the National Fire Protection Association (NFPA). Thomas is involved with and chairs various committees for NEMA and IEEE and is an Alternate member on NFPA 73. He is very active in the state by state adoption process of NFPA 70 working closely with review committees and other key organizations in this effort.