Skip to main content


The Skinny on Confined Spaces

There are rules in our industry. We, as utility or utility contractor employers, must follow the rules for two reasons. The first reason is that, if we don’t follow the rules, we get into trouble with the regulatory authorities. The second and more important reason is that the rules are in place to protect employees from injury or death. So it is with confined spaces. Confined spaces can and have killed workers.

Confined space is a confusing issue among many of our colleagues and one I get questions about all the time. In fact, a recent inquiry about confined spaces in wind generation spurred this article. We will first look at the classification of the spaces we work in so that you start from the right perspective as you try to comply with the rules and effectively protect your workers without going way beyond what’s required. Then we will look at how to practically apply the rules in our workplaces.

The Statistics

According to the U.S. Bureau of Labor Statistics’ Census of Fatal Occupational Injuries, manholes and vaults are the third most frequent locations for confined space deaths. The most common sources of fatal exposure are naturally occurring hydrogen sulfide, carbon monoxide and naturally occurring methane. Trench collapses killed 168 workers in 2020, the year of the most recent census report. Yes, trenches can be confined spaces. 

Looking at the exposure statistics should get our attention. Those spaces are where we work. And we have another emerging confined space issue related to wind generation. There are no census reports yet because wind turbine maintenance is just getting into swing as turbines age and maintenance intervals increase, but we know injuries and fatalities are increasing, too. 

OSHA requires every employer to examine their workplace for confined space hazards and develop a plan for worker protection. 

The utility industry has a special classification known as an “enclosed space.” For all practical purposes, we have two classifications: permit-required confined space and enclosed space. Let’s start with some definitions. Permit-required confined space regulations are found at 29 CFR 1910.146 (Subpart J) and 1926 Subpart AA. Enclosed space standards are found at 1910.269(e) and 1910.269(t). You must be familiar with 1926 Subpart AA and 1910.146 so that you clearly know what a permit-required space is and when a location is considered one (more on that in a bit). Your utility’s enclosed space program and training must be based on 1910.269(e) and 1910.269(t). So, now let’s look at how all this fits together for practical application and keeping your workers safe.  

Understanding Definitions

First, we need to understand the definitions of the spaces we work in. For those, we go right to the definitions in the OSHA standard for permit-required confined spaces in 1910.146. We must also go to the end of 1910.269, where we will find the definitions for keywords used in the 1910.269 standard. Each definition from the standard is followed by an explanation.

“Confined space” means a space that:

  1. Is large enough and so configured that an employee can bodily enter and perform assigned work; and
  2. Has limited or restricted means for entry or exit (e.g., tanks, vessels, silos, storage bins, hoppers, vaults and pits are spaces that may have limited means of entry); and
  3. Is not designed for continuous employee occupancy.

Explanation: This definition does not cover electrical manholes, vaults or wind towers. First, all three defining characteristics must be present. While condition 1 might be construed as a manhole, walk-in vault or subterranean electrical vault, that assumption is clarified by conditions 2 and 3. Condition 2 uses examples to help readers understand the term “restricted means for entry.” These restricted means are typically flanges or plates fastened in place with several bolts, meaning it takes a very purposeful act to try to enter the space. You can also surmise from this description the types of facilities these spaces are in. Condition 3 further clarifies the space as “not designed for continuous employee occupancy.” The word “designed” means that the entryways are engineered for access with space and hardware to facilitate frequent and relatively convenient access. Inside the space is appropriate room for maneuvering, walkways, walking grates, handholds, covers for hazardous equipment, lighting and/or ventilation. “Continuous employee occupancy” means that it is expected and common for employees to routinely enter the space for operation, maintenance or inspection. 

“Non-permit confined space” means a confined space that meets the definition of a confined space but does not meet the four conditions (see below) of a permit-required confined space.

Explanation: The purpose of this definition and the way it is written have to do with mitigating any of the four hazards that make a space a permit space. This practice is known as reclassifying a permit space. If you have a permit space, but you mitigate or control the four hazards called out in the definition for a permit-required confined space, that space is now a confined space, recognizing that if any of the mitigated hazards reoccur, that space is instantly now a permit space. Following are the four conditions that make a confined space a permit space.

A “permit-required confined space” means a confined space that has one or more of the following characteristics:

  1. Contains or has the potential to contain a hazardous atmosphere.
  2. Contains a material that has the potential for engulfing an entrant.
  3. Has an internal configuration such that an entrant could 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 hazard.

Explanation: Characteristic 1 is frequently cited as justification for making a manhole a confined or permit space. The reasoning is that, should a fire occur, a hazardous atmosphere would exist. The assumption is true – a hazardous atmosphere would exist – but it does not apply to manholes or vaults. This definition is about confined spaces that are classified as permit spaces. A manhole or an electrical vault does not meet the configuration for a confined space established in the definitions, so this characteristic is not associated with electrical manholes or vaults. This definition also exempts wind towers for the same reason. Characteristic 2 refers to flowing materials, such as water, or flowable solids, such as seed. Characteristic 3 refers to bottom-dispensing hoppers or storage bins. Sloping walls do not relate to manholes, electrical vaults or wind towers. Characteristic 4 is also used to include manholes because electricity is hazardous, and vaults or manholes can contain hydrogen sulfide or carbon monoxide. While this is true, as is the case in characteristic 1, these electrical spaces don’t meet the configuration requirements of a confined space.

So, a confined space has to do with shape and access, while a permit-required confined space has to do with the hazards within the confined space.

An “enclosed space” is defined as a working space – such as a manhole, vault, tunnel or shaft – that has a limited (different from “restricted” in confined space) means of egress or entry; that is designed for periodic employee entry under normal operating conditions; and that, under normal conditions, does not contain a hazardous atmosphere, but may contain a hazardous atmosphere under abnormal conditions.

Note to the definition of “enclosed space”: OSHA does not consider spaces that are enclosed but not designed for employee entry under normal operating conditions to be enclosed spaces for the purposes of this section. Similarly, OSHA does not consider spaces that are enclosed and that are expected to contain a hazardous atmosphere to be enclosed spaces for the purposes of this section. Such spaces meet the definition of permit spaces in 1910.146, and entry into them must conform to that standard.

Explanation: Now we get to the space particularly defined for the electric utility industry, the enclosed space. Rule 1910.269(e), “Enclosed spaces,” explains that the enclosed space classification is in lieu of the permit-space entry requirements contained in 1910.146. This rule further requires that if, after the employer takes the precautions required by paragraphs (e) and (t) of 1910.269, the hazards in the enclosed space endanger the life of an entrant or could interfere with an entrant’s escape from the space, then entry into the enclosed space shall meet the permit-space entry requirements of 1910.146. This is a very important rule because it clarifies that 1910.269(e) does not stand alone as work rules for manholes and vaults. Section (t), “Underground electrical installations,” is part of the requirements for the protection of workers in enclosed spaces. You must be familiar with and follow both to get it right. 

Another Look

Let’s look again at the definition for “enclosed space,” particularly the note to the definition. In simple terms, the note shares two important perspectives from which we interpret the rules of 1910.269(t). First, if it is designed for employee entry, it is not a permit space. Second, if the space is expected to contain a hazardous atmosphere, it is not an enclosed space. Again, this is important in defining an enclosed space, particularly when dealing with basements of wind towers or the nacelle. In a normally operating system, the presence of oil, hydraulics, or electrical equipment and cables is not considered a hazardous atmosphere or other hazard. This is a key issue for manholes and electrical vaults, especially regarding rescue, and here is why.

Remember, a manhole is covered by both 1910.269(e) and (t). Part (t) requires a first-aid-trained attendant on the surface if the manhole has energized cables or equipment. Part (t) also allows the attendant to enter the manhole for short periods to provide non-emergency assistance. Part (e) requires an attendant as well. The part (e) enclosed space attendant must be first-aid trained and is not permitted to enter the space to assist workers inside. In fact, the rule uses the phrase “immediately available outside the enclosed space,” and those duties performed by the attendant must not distract the attendant from monitoring employees within the space or ensuring that it is safe for employees to enter and exit the space. So, why the difference? It is explained in the preamble. Part (t) specifies that the hazard is “electrical contact” to the exclusion of all other hazards. Part (e) includes other hazards such as gases, water and fires/explosions. Where the only hazard has been determined to be contact with an exposed electrical hazard, an attendant can briefly enter the space. 

The Bottom Line

The bottom line on rescue from a manhole, vault or wind enclosed space is this: OSHA makes it clear in the preamble to 1910.269 that the intention is to have a space for the electric utility industry that recognizes both the nature of enclosed spaces and the types of tasks we perform in those spaces. Wind is somewhat different in configuration, but it is still electric utility generation, transmission and distribution, so we still benefit from that. 

Here is a summary of what you should know about enclosed spaces:

  • OSHA’s intent is that all confined spaces are hazardous until they are classified by a competent person and remediated to make the space safe to enter. Otherwise, they shall be treated as permit spaces. 
  • OSHA also intends that a competent person must classify electrical manholes, vaults, tunnels or shafts as enclosed spaces in accordance with the standard before workers enter those spaces.
  • Classification of an enclosed space requires detection of flammable gases, toxic fumes and oxygen levels.
  • Where unacceptable atmospheres require ventilation, gas checks must assure the ventilation is effective prior to any entry.
  • Where electrical systems exist, a competent person must inspect and assure the integrity of the insulating systems. 
  • A manhole or vault that’s only hazard is electrical shock requires an attendant who can occasionally enter the space to assist workers (see 1910.269(t)(3)(ii)).
  • An enclosed space has more potential hazards, not just electrical hazards, so an enclosed space attendant cannot enter the space (see 1910.269(e)(7)).
  • Enclosed space rescue where a hazardous atmosphere exists (e.g., smoke, fire, gas, toxic fumes) must be non-entry rescue. This requirement means enclosed space entrants must be equipped with rescue lines.
  • A manhole or vault that has come to contain any hazardous condition, such as smoke, gas or flood, is a permit space and non-entry rescue must be performed, meaning the entrants must be in a harness and lifeline where those potential hazards exist. 
  • Entry rescue must be made by a qualified person in protective gear, and an attendant must be on the surface during the rescue entry. 
  • Any space that has a hazardous atmosphere must be effectively ventilated or treated as a permit space.
  • Workers around any confined space of any classification must be trained to the requirements of the 1910.269 standard before they enter or serve as an attendant.

Some Final Notes on Wind

When it comes to wind generation, rescue for a basement or the bottom of a tower is not too difficult to figure out and plan for. The nacelle has proved to be more difficult, and we have had several bad outcomes in those spaces in the past decade. The nacelle gets surveyed for hazards by a competent person just like a manhole does. If hazardous conditions are discovered, remediation must occur. Leaking fluids is a big one, especially if they are flammable. 

Egress from a nacelle is either down the ladder or out the top hatch. If the exit is the top hatch, timely rescue must be in the plan. The roof rescue is often a rappel, so that equipment must be in place while the work is going on. Rappelling should also be considered down the ladder. In a fire, it is much faster to rope down the ladder than to climb down it. 

About the Author: After 25 years as a transmission-distribution lineman and foreman, Jim Vaughn, CUSP, has devoted the last 24 years to safety and training. A noted author, trainer and lecturer, he is a senior consultant for the Institute for Safety in Powerline Construction. He can be reached at

Train the Trainer 101, Current

Jim Vaughn, CUSP

After 25 years as a transmission-distribution lineman and foreman, Jim Vaughn, CUSP, has devoted the last 24 years to safety and training. A noted author, trainer and lecturer, he is a senior consultant for the Institute for Safety in Powerline Construction. He can be reached at