Lost in Confined Space

Each year, thousands of workers are injured or killed in confined spaces such as tanks, crawlspaces, trenches, and tunnels. In many instances, the confined space was not recognized as such, or the potential danger was downplayed.

An individual whose line of work involves infrequent visits to a confined space can be exposed to the same hazards as a tradesperson whose job involves working entire shifts in a confined space. Such occasional visitors can be considered contractors on the site of host employers, and include engineers, adjusters, inspectors, surveyors, and safety/loss control specialists.

The question arises; can such individuals clearly recognize a confined space and the potential hazards associated with a confined space? The OSHA standard on Permit-Required Confined Spaces (29CFR 1910.146) provides some insights.

5354478916_a68ecab262_mConfined Spaces versus Permit-Required Confined Spaces

A key to this OSHA standard is understanding a “confined space” and a “permit-required confined space”. Confined spaces are often stereotyped as tanks or other types of enclosed vessels. A confined space can be virtually any partially or fully enclosed area. The criteria that define a confined space are:

The space 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; and is not designed for continuous employee occupancy.

All three items must apply for an area to be termed a confined space. Examples of confined spaces include excavations, trenches, boilers, work pits, manholes, tunnels, pipelines, sewers, silos, storage vessels, sumps, process tanks, crawlspaces, and digesters.

For a permit-required confined space to exist, an area must first be categorized as a confined space, meeting all three of the aforementioned criteria. Second, the area must have one or more of the following characteristics:

Contains or has a potential to contain a hazardous atmosphere; or contains a material that has the potential for engulfing the entrant; or 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.


Hazardous atmospheres kill more people than all other confined space hazards combined. In a National Institute for Occupational Safety and Health (NIOSH) study of confined space fatalities, 81 percent resulted from toxic/oxygen deficient atmospheres. Hazardous atmospheres are those which are:

  1. Oxygen deficient/enriched (less than 19.5 percent/greater than 23.5 percent)
  2. Flammable, combustible, or explosive
  3. Toxic
  4. Irritating and/or corrosive

Hazardous atmospheres can cause unconsciousness and death very quickly. Hydrogen Sulfide, a byproduct of organic decomposition found in sewers and sewage treatment plants, can cause death in a matter of minutes.

An engulfment hazard involves liquids and flowable solids that could surround and capture a person, resulting in suffocation or constriction-related death.

Configuration hazards exist where the shape of a space can entrap a person. Tapered or funnel shaped spaces are examples of configuration hazards.

Recognized serious hazards include electrical systems, mechanical components, chemicals, biological agents, potential for explosion, and temperature extremes.

Host Employer Requirements

Host employers, those having control over the specific facility or job site, are required to develop and implement comprehensive confined space programs. The host employer has a responsibility for the safety of all workers on site, including contractors on the site of host employers; i.e., those not directly employed by the host who come on site to provide a service.

Confined space related hazards do not discriminate between host employers and contractors on the site of host employers. Contractors should have a basic understanding of confined spaces, permit-required confined spaces, and associated hazards. For their own safety, these individuals should be able to identify conditions and situations where a host employer should be expected to have a confined space program in effect. Contractors should realize the responsibilities of the host employer, including:

  1. Identifying all permit-required confined spaces in their workplaces
  2. Preventing unauthorized entry into these workplaces
  3. Protecting workers from all identified hazards

For specific confined space/permit-required confined space requirements, please refer directly to § 1910.146 – Permit-required confined spaces, of the OSHA General Industry Standard (1910).

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