Posted On: February 17, 2023

Confined Space Definition: What Are Confined Spaces?

The occupational safety and health field has many terms that don't sound like jargon but have a very specific meaning.

We've talked in the past about a competent person as one example.

Confined space is another.

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The Technical Definition Of Confined Spaces

According to 29 CFR 1910.146(b), OSHA's definition of 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."

Permit-required confined spaces, or 'permit spaces' for short, are confined spaces that have one or more additional dangerous 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."

What Is a Confined Space, Really?

Regulatory language has to be specific so it can be enforced, but that often makes it convoluted.

In plain language, a confined space is one that:

  • Is big enough for someone to climb into for work, and
  • Has limited options for human access, but
  • Isn't designed for a person to spend time in

If a workplace has an area that meets those requirements, then employers are required to evaluate the space for hazards that would make it a permit space (like the possibility that someone could suffocate or get stuck).

If it turns out it is a permit-required confined space, then there are a lot of other safety regulations the employer needs to follow.

OSHA's confined space definitions are designed around a specific category of workplace hazards that share similar precautions. Understanding what makes a confined space dangerous is the key to understanding the definition itself and recognizing what counts as a confined space to OSHA.

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Why is Working in a Confined Space Dangerous?

OSHA has very specific technical definitions of various confined space hazards so that employers and regulators know the exact point at which something is too hazardous.

We're going to stick to a plain-language summary of the reasons a confined space can be dangerous to the people working inside.

Difficulty Entering or Exiting

The most important thing that defines a confined space is that it's difficult to get into (and therefore, out of). If something goes wrong when a worker is inside, escape or rescue can be complicated.

This doesn't necessarily mean confined spaces have a single (or even small) access point. You might think a door – rather than a manhole or hatch – makes a space exempt, but the size and location of the door will matter, as well as the presence of any equipment that needs to be crawled over, under, or squeezed around.

In fact, not all confined spaces are fully enclosed. Partially enclosed spaces can have the same hazards. Even open-topped spaces may count as confined spaces if you need equipment like ladders or hoists to get in and out.

Poor Ventilation

Since a confined space is partially or fully enclosed and not designed for people to spend time in, they're also poorly ventilated.

Combine this with the fact that many confined spaces have (or had) hazardous substances inside, and a confined space can easily develop a hazardous atmosphere.

Essentially, a hazardous atmosphere is one that involves:

  • Too little (or too much) oxygen
  • Buildup of flammable or combustible elements in the air
  • Buildup of airborne contaminants that can make you sick

Possibility of The Space Filling Up

Another major hazard of a confined space is "engulfment," which covers both flooding and being buried by what's called a free-flowing solid. Free-flowing solids are "finely divided" items like grain, mud, and dirt.

A confined space can quickly fill up, leading to your "effective capture," as OSHA puts it. You might end up breathing a liquid or fine solid in, and free-flowing solids can easily press in on your body, leading to strangulation, constriction, or crushing.

Possibility of Getting Stuck

Some confined spaces have converging walls, sloping floors, tapered areas, or intrusive pipes, machinery, or other heavy and fixed items.

Depending on the design, a person can get wedged and trapped in these spaces after slipping, falling, or trying to squeeze into an area. Getting trapped can lead to asphyxiation.

In confined spaces that have mechanical hazards, it's also possible for one of these "entrapping designs" to accidentally push someone into dangerous machinery.

Difficulty Communicating

In a confined space, it might be difficult for anyone on the outside to see or hear a person on the inside.

This makes the inherent dangers of a confined space even riskier because if something goes wrong, the rest of the team might not even know you need rescue.

Even if they do, the strange acoustics of small spaces may make it difficult to be understood, complicating extraction.

Confined Space Examples

People who perform industrial, maintenance, construction, maritime, and agricultural work often encounter confined spaces.

Non-Permit Confined Spaces Examples

Some areas fit the definition of a confined space, but don't or couldn't have any hazards that might cause death or serious harm. These are called non-permit confined spaces, and as long as someone has assessed the potential for hazards first, you don't need special precautions to enter them.

Examples of confined spaces that don't require permits include:

  • Equipment closets
  • Machinery cabinets
  • Ventilated tunnels
  • Drop ceilings

Permit-Required Confined Space Examples

Unfortunately, it's easier to find a dangerous confined space in your workplace than it is a relatively safe one.

There's a long list of confined space examples that usually require permits and precautions:

  • Sewers, storm drains, underground pipes, tunnels, and tunnel systems
  • Storage tanks, vats, or vessels designed to hold liquids, gases, or free-flowing solids
  • Excavations or trenches, which may collapse or flood with little notice
  • Pipes, ducts, conduits, and flues that are big enough to enter
  • Manholes, access shafts, and lifts
  • Industrial boilers, incinerators, scrubbers, and similar chambers
  • Inspection and maintenance pits for vehicles, escalators, or other equipment
  • Industrial pits, mining pits, and cesspools
  • Utility and storage vaults
  • Silos and hoppers
  • Wet or dry wells
  • Cargo holds and void spaces
  • Unventilated areas or rooms on any floor

A few other examples of confined spaces may or may not require a permit, depending on the circumstances and design:

  • Boiler rooms
  • Enclosed chambers
  • Crawl spaces

What is OSHA's Confined Space Requirement?

OSHA actually has three confined space standards:

  • Maritime (shipyard) industry's standard can be found under §1915 Subpart B
  • Construction industry's standard, effective 2015, is located under §1926 Subpart AA
  • General industry (ie, everyone else) abides by the standard under §1910.146

The general confined space requirements for all three "industries" are similar – employers need to assess confined spaces for permit status, follow all permitting rules, perform atmospheric testing, take precautions to minimize exposure to any hazards, and have a rescue plan.

You also need to use signage and training to make employees aware of confined space hazards and teach them how to comply with OSHA's requirements for their own safety.

The safest (and easiest!) way for employers to ensure they fulfill OSHA's confined space training requirement is to rely on courses from an OSHA-authorized provider like us.

We offer multiple online OSHA confined space courses tailored to the different needs of your employees. Some only need a short awareness training while others need extensive entry training, and then there's the construction vs general industry divide.

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