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Enclosed and Confined Spaces

What’s the difference?

The terms “enclosed” and “confined” seem like synonyms. When most of us think of something that is enclosed, we think of it as being confined, and when we think of a confined place, we think of it being somewhat enclosed. How we visualize these two words often accounts for why we have difficulty understanding their differences when it comes to OSHA standards. The enclosed spaces standard is one of the most misinterpreted standards in 29 CFR 1910.269. This standard is often used by utilities and contractors in lieu of the permit-required confined space standard because the assumption is, qualified electrical workers enter a space to perform electrical work, so therefore the enclosed spaces standard applies. But is that a correct assumption?

OSHA standards typically have an application section to inform employers and workers when a specific standard applies. The application section of the enclosed spaces standard, found at 1910.269(e), states, “This paragraph applies to routine entry into enclosed spaces in lieu of the permit-space entry requirements contained in paragraphs (d) through (k) of §1910.146.” That sentence is followed by this statement: “If, after the employer takes the precautions given in paragraphs (e) and (t) of this section, the hazards remaining 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 paragraphs (d) through (k) of §1910.146.”

At first glance, it may appear as though there is no difference between an enclosed space and a confined space. However, there is a specific word that OSHA includes in the application of this standard: “routine.” What does routine mean and why did OSHA include it? The answer to those questions is the intent and reason behind this entire standard’s existence. OSHA states the following in the preamble to 1910.269: “Work in these spaces is part of the day-to-day activities performed by employees protected by this standard.” Routine work, according to OSHA, means part of the day-to-day activities. Workers who enter a space a few times a year or even a few times a month are not routinely entering those spaces – and therefore the enclosed spaces standard does not apply.

An enclosed space and a permit-required confined space have many similarities, and in fact, most enclosed spaces would be considered permit-required confined spaces if the enclosed spaces standard did not exist. For example, enclosed spaces include manholes, vaults, tunnels and shafts that have limited entry and egress; these spaces could easily be considered permit-required confined spaces as well. Employers are required to have safe work practices for entering both types of spaces, and training requirements are also similar between the two. Workers who enter both types of spaces are required to be trained in the procedures and hazards associated with the spaces they enter. Attendants for both spaces are required to be trained in emergency rescue procedures. This includes proper equipment (e.g., tripod, davit arm) setup and usage as well as how to notify the proper emergency response unit.

Hazard identification and mitigation are a big part of both standards, and both require evaluation of potential hazards prior to entry. This includes testing the atmospheric conditions of each space to ensure the air quality is safe for a worker to enter. Additionally, both standards require the use of ventilation if a hazardous atmosphere is found.

Although the two standards have similarities, there are also some significant differences. For example, let’s consider each of their definitions.

According to 1910.146, “Permit-required confined spaces,” a confined space is “a space that is large enough and so configured that an employee can bodily enter and perform assigned work; and has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry); and is not designed for continuous employee occupancy.” Further, a permit-required confined space is “a confined space that has one or more of the following characteristics: contains or has a potential to contain a hazardous atmosphere; contains a material that has the potential for engulfing an entrant; has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section; or contains any other recognized serious safety or health hazard.”

OSHA defines an enclosed space in 1910.269 as a “working space, such as a manhole, vault, tunnel, or shaft, that has a limited 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.”

Although these two spaces seem similar, there are a few subtle differences between them, such as “not designed for continuous employee occupancy” versus “designed for periodic employee entry under normal operating conditions.”

Attendant requirements are another significant difference between the two standards. An attendant is required at all permit-required confined spaces, and OSHA describes a long list of their required duties. However, an attendant is only required outside of an enclosed space “if a hazard exists because of traffic patterns in the area of the opening used for entry” (see 1910.269(e)(7)) or when work is performed inside manholes and vaults with energized electric equipment.

The last major difference is the requirement for a permit. Obviously, a permit-required confined space requires a permit, however, no permit is required when performing work under the enclosed spaces standard. A permit is a form that is used as a checklist to ensure the proper precautions are in place before, during and after entry into the space. There are specific requirements for information that is to be included on the permit, including the names of entrant(s) and attendant(s), air monitoring results and emergency response procedures.

So, is there really a difference between an enclosed space and a confined space? The answer is yes and no. For most of these types of spaces, there is no discernible difference, and as mentioned earlier, most of these spaces would likely be classified as permit-required confined spaces if the enclosed spaces standard did not exist. So, why does it exist? The enclosed spaces standard was developed specifically for workers who work in an underground utility system on a day-to-day basis; these systems are typically found in large metropolitan areas. In contrast, the standard was not developed for workers who may enter a confined space periodically throughout a month or a year.

Workers who enter a space only a few times a year would most likely need to be reminded about the expectations and specific requirements for entry, which is a good reason to have a permit in place. As mentioned earlier, the permit serves as a checklist to ensure the correct controls are used throughout the process. Workers who enter these spaces routinely, however, have a different perspective. They utilize these controls as part of their daily work activities. But regardless of the classification of the space, hazards must still be identified and properly controlled.

About the Authors: Pam Tompkins, CUSP, CSP, is president and CEO of SET Solutions LLC. She is a 40-year veteran of the electric utility industry, a founding member of the Utility Safety & Ops Leadership Network and past chair of the USOLN executive board. Tompkins worked in the utility industry for over 20 years and has provided electric power safety consulting for the last 20-plus years. An OSHA-authorized instructor, she has supported utilities, contractors and other organizations operating electric power systems in designing and maintaining safety improvement methods and strategies for organizational excellence.

Matt Edmonds, CUSP, CIT, CHST, is vice president of SET Solutions LLC. A published author with over 15 years of safety management experience, he also is an OSHA-authorized instructor for general industry and construction standards. Edmonds provides specialty safety management services for electric power organizations throughout the U.S. He has been instrumental in the development of training courses designed for electric power organizations, including OSHA 10- and 30-hour courses and SET Solutions’ popular OSHA Electric Power Standards Simplified series.

About OSHA Electric Power Standards – Simplified: Topics in this series are derived from SET Solutions’ popular OSHA electric power course offered through the Incident Prevention Institute ( The course is designed to help learners identify standard requirements and to offer practical ways to apply the standards.