New Confined Spaces in Construction Standard from OSHA: 1926 Subpart AA, 1926.1200

[Note: This is an old article written in 2013. It has some useful information about confined spaces, but if you’re looking for current information about the brand-new (2015) confined spaces in construction rule, click here].

OSHA’s most recent Unified Agenda announced that they’ll be creating a new Confined Spaces in Construction Standard. So, we’ve pulled together a bunch of information on confined spaces in construction to help you prepare.

According to OSHA, nearly 6.5 people die, and 967 people are injured, in confined spaces at construction sites every year. So the hazards and risks are real.

OSHA believes that the new standard can prevent six of those deaths and 880 of those injuries every year.

What Type of Hazards Are Present in Confined Spaces at Construction Sites?

OSHA breaks the hazards down into two large categories: inherent hazards and induced hazards.

Inherent hazards
are associated with specific types of equipment and the interactions among them. These hazards can’t be eliminated without degrading the system or equipment, or without making them inoperative. As a result, the emphasis must be on controlling these hazards. These hazards include high voltage, radiation generated by equipment, defective design, omission of protective features, high or low temperatures, high noise levels, and high-pressure vessels and lines.

Induced hazards
arise and are created when people make incorrect decisions and take incorrect actions during the construction process. Examples include omission of protective features, physical arrangements that cause unintentional worker contact with electrical energy sources, oxygen-deficient atmospheres created at the bottom of pits or shafts, lack of safety factors in structural strength, and flammable atmospheres.

What Are Hazards of Typical Confined Spaces?

Below are some typical examples of confined spaces in construction that include inherent and induced hazards (according to OSHA).

Workers often must enter vaults. The restricted nature of the vaults, and the fact that they’re frequently located below grade, can create a number of safety and health problems (as you’ll see in many of the examples below).

Oxygen-Deficient Atmospheres
While working in vaults, a major problem workers face is the possibility of an oxygen-deficient atmosphere.

Explosive or Toxic Gases, Vapors, or Fumes
While working in an electrical vault, explosives gases such as propane may build up. In addition, welding and soldering inside the space can produce toxic fumes.

Electrical Shock
Electrical shock may occur from power tools, line cords, and similar equipment. This often happens because the contractor has not provided an approved grounding system or provided the protection afforded by ground-fault circuit interrupters or low-voltage systems.

In some cases, purging agents such as nitrogen and argon may enter a vault from areas adjacent to it. These purging agents can displace the oxygen in the vault and cause workers to asphyxiate, sometimes immediately.

Materials Falling In and On
Material or equipment may fall into the vault or onto workers as they enter and leave the vault. If manhole covers were removed, or if they were not installed in the first place, materials can fall in, injuring workers inside.

Condenser Pits
A confined space often found at nuclear power plants is the condenser pit. These are often overlooked as a potentially hazardous confined space, but this is a mistake. These below-grade areas create large areas in which toxic fumes, gases, and similar hazards can accumulate. In addition, they provide areas for oxygen-deficient atmospheres to develop when purging with argon, freon, and other inert gases. Other hazards can be created by workers above dropping equipment, tools, and materials into the pit.

A number of hazards are associated with manholes. First, they can be a dangerous trap into which a worker could fall. Covers are often (but wrongly) removed and not replaced, or else they are not provided in the first place.

Pipe Assemblies
This is a frequently unrecognized confined space. For any number of reasons, workers enter pipes. Once inside, they may be faced with oxygen-deficient atmospheres, often caused by purging with argon or another inert gas. In addition, welding fumes generated by the worker in the pipe, or by other workers operating outside the pipe, may subject the worker to toxic atmospheres. Once a worker is inside the pipe, communication and extraction become difficult, especially in situations when the pipe bends. Another problem that may occur is electrical shock caused by ungrounded tools and equipment or inadequate line cords. Finally, heat within the pipe can cause the worker to suffer heat prostration.

Ventilation Ducts
These sheet metal enclosures are also common at construction sites, and workers often enter them to cut out access holes, install essential parts of the duct, and more. Hazards that ventilation ducts pose include oxygen deficiency, difficult entry and exit, difficult communication, electrical shock hazards, and heat stress.

Tanks are yet another common confined space at construction areas. Workers may enter tanks to clean them and perform repairs. Ventilation in tanks is always a problem, and oxygen-deficient atmospheres, toxic atmospheres, and explosives atmospheres sometimes result. Heat may cause the worker to suffer heat prostration. Because workers often take electrical line cords into the tank, electrical shock is a real hazard. And finally, workers often have to use ladders to enter and exit these, presenting yet another hazard.

Workers entering sumps may encounter oxygen-deficient atmospheres. Another hazard is presented by the wet nature of the sump, which contributes to electrical shock hazards. Finally, the low light levels often cause accidents.

Containment Cavities
These large, below-grade area often have little or no air movement, making ventilation a problem. In addition, an oxygen-deficient atmosphere may exist. If welding and other gases collect in this areas, toxic atmospheres arise. And as these structures near completion, more confined spaces will exist as rooms are built off the existing structure.

Electrical Transformers
Electrical transformers often contain a nitrogen purge or dry air. It’s important to vent these by having air pumped in before they are opened. Before entering, test for oxygen deficiency and for toxic atmospheres (this is mandatory).

Heat Sinks
When in these pits, workers are exposed to welding fumes and electrical hazards, particularly because water accumulates in the bottom of the sink. Generally, it is hard to communicate with workers in a heat sink, because the rebar in the walls of the structure deaden radio signals.

Confined Space Within a Confined Space
One of the most hazardous situations of all is a confined space inside another confined space. The very nature of construction work often causes these situations to arise. Examples include tanks within pits, and pipe assemblies or vessels within pits. In these situations, potential hazards associated with both confined spaces (the inner and outer) require testing, monitoring, and control, but in many cases, these procedures are performed only on the outer confined space.

Hazards in One Space Entering Another
While one confined space may be relatively safe for work, access passages from other areas outside or adjacent to the space could, at some point, allow the transfer of hazardous agents into the confined space that once seemed “safe.” For example, a pipe coming through the wall into a container room could create a situation like this, as welding fumes and other toxic materials generated in a different area travel through the pipe and into the “safe” confined space (and, obviously, making it unsafe). A serious problem with this kind of situation is that the workers in the confined space thought to be safe are unaware of the hazards leaking into the area and so they are therefore not prepared to take action to avoid or control it.

What Standards Currently Address Confined Spaces in Construction?


All employees required to enter into confined or enclosed spaces shall be instructed as to the nature of the hazards involved, the necessary precautions to be taken, and in the use of protective and emergency equipment required. The employer shall comply with any specific regulations that apply to work in dangerous or potentially dangerous areas.

Click here for Standard Interpretations of 1926.21(b)(6)(i)


For purposes of paragraph (b)(6)(i) of this section, “confined or enclosed space” means any space having a limited means of egress, which is subject to the accumulation of toxic or flammable contaminants or has an oxygen deficient atmosphere. Confined or enclosed spaces include, but are not limited to, storage tanks, process vessels, bins, boilers, ventilation or exhaust ducts, sewers, underground utility vaults, tunnels, pipelines, and open top spaces more than 4 feet in depth such as pits, tubs, vaults, and vessels.

Click here for Standard Interpretations of 1926.21(b)(6)(ii)

1926 Subpart J – Welding and Cutting

1926 Subpart P – Excavations

1926 Subpart S – Underground Construction

1926.956—Underground Electric Transmission and Distribution Work

What Resources Does OSHA Currently Offer Regarding Confined Spaces in Construction?

Confined Space in Construction Safety and Health Topic Webpage
A nice overview of links and information.

Anatomy of Confined Spaces in Construction
An introduction to the types of hazards (inherent and induced), typical confined spaces, and unusual conditions.

Overview of Regulations Concerning Confined Spaces In Construction
Tons of helpful outreach information.

Construction Industry Safety and Health Outreach Program
More helpful information and resources.

Construction Pocket Guide
Overview of construction hazards and solutions; safety and health resources; cooperative and state programs; and safety success stories.

Where Will I Be Able to Find this New Rule In the Regulations (Once It Exists)?

It looks like it will be 1926 Subpart AA, 1926.1200.

Does OSHA Have Information about the New Proposed Rule?

Not about the current version of new proposed rule, but here’s a document titled Confined Spaces in Construction (Proposed Rule) that discusses the version proposed in 2007. Since then, there has been a comments period and those comments are being incorporated into the rule that will be released in 2013. Much of the information in this post is drawn from this OSHA document.

Has OSHA Summarized the New Standard?

No. But they DID summarize the proposed rule in 2007, before the comments period and any incorporation of those comments, so here’s that information:

Definition of Confined Space:
A space that is large enough and arranged in such a manner that employees can enter the space, has limited or restricted means of entry/exit and is not designed for continuous employee occupancy.

Employers’ First Responsibility:
Determine if there is a confined space at a job site.

If There is a Confined Space:
Determine if there are existing or potential hazards in the space.

If There Are Hazards:
Classify the space according to the physical and atmospheric hazards found in it.

The Four Hazard Classifications:
Isolated-Hazard Confined Space, Controlled-Atmosphere Confined Space, Permit-Required Confined Space, and Continuous System-Permit-Required Confined Space

Isolated-Hazard Confined Space:
A confined space that has any one of the following characteristics: A hazardous atmosphere; an inwardly converging, sloping, or tapering surfaces that could trap or asphyxiate an employee (for example, a space between walls that narrows towards the base, including, but not limited to, funnels and hoppers); or an engulfment hazard or other physical hazard. This definition is similar to the definition in the general industry standard, but includes more examples of dangerous configurations of confined spaces.

Controlled-Atmosphere Confined Space:
A confined space that has all of the following characteristics: Contains no physical hazards or only isolated physical hazards; and uses ventilation alone to control atmospheric hazards at safe levels. This term was added to designate a distinct type of confined space in which only one type of hazard (atmospheric) is present that requires a specific type of employee protection–active control of the atmospheric hazard at safe levels by ventilation equipment. OSHA believes that the space described by this definition is similar to the space defined by the alternate procedures specified by paragraph (c)(5) of the general industry standard for confined spaces. Both of these spaces involve conditions in which atmospheric hazards are merely controlled by ventilation instead of eliminated completely. Therefore, if the ventilation system stops or malfunctions, the atmospheric hazards could reemerge in the space. Unlike the general industry standard, the proposed standard for construction assigns a name to the space. OSHA believes that naming the space a Controlled-Atmosphere Confined Space will effectively alert employees, especially employees who have little or no experience with these spaces, to the possibility that atmospheric hazards could reemerge in the space if the ventilation system stops or malfunctions.

Permit-Required Confined Space:
A confined space that has any one of the following characteristics: A hazardous atmosphere; an inwardly converging, sloping, or tapering surfaces that could trap or asphyxiate an employee (for example, a space between walls that arrows towards the base, including, but not limited to, funnels and hoppers); or an engulfment hazard or other physical hazard. This definition is similar to the definition in the general industry standard, but includes more examples of dangerous configurations of confined spaces.

Continuous System-Permit-Required Confined Space:
A Permit-Required Confine Space that has all of the following characteristics: Is part of, and contiguous with, a larger confined space (for example, sewers); the employer cannot isolate it from the larger confined space; and is subject to a potential hazard release from the larger confined space that would overwhelm personal protective equipment and/or hazard controls, resulting in a hazard that is immediately dangerous to life and health. This classification of space was mentioned in 29 CFR 1910.146(c)(5)(i), and a sample Permit-Required Space program for sewers was provided in Appendix C of that standard.

OSHA believes it is important to define this classification of confined space in a way that emphasizes that it is subject to a potential hazard release, such as an engulfment hazard, that the employer will not be able to control.

What Are the Major Differences Between the Confined Spaces in General Industry and the Confined Spaces in Construction Standards Proposed in 2007?

Difference General Industry Construction
Organization of Standard Begins with requirements for entering PRCS. Takes a step-by-step approach, explaining how to assess hazards, determine the classification for the space, and how to safely enter it.
Information Exchange Host employer coordinates entry operations with a contractor when the host employer and the contractor both have employees working in or near a permit space. Controlling contractor coordinates entry operations among contractors who have employees in a confined space regardless of whether or not the controlling contractor has employees in the confined space.
Confined Space with Hazards Isolated Doesn’t address working in confined spaces in which hazard has been isolated. Allows employers to establish an Isolated-Hazard Confined Space by isolating or eliminating all physical and atmospheric hazards in a confined space.
Controlled-Atmosphere Permit-Required Confined Space Monitoring required as necessary. Continuous monitoring required unless the employer demonstrates that periodic monitoring is sufficient.
Permit-Required Confined Spaces–Entry Supervisors No explicit requirement for entry supervisor to monitor PRCS conditions during entry. Explicit requirements for entry supervisor to monitor PRCS conditions during entry
Permit-Required Confined Spaces–Written PRCS Plan Requires a written PRCS plan. No written plan required when employer maintains a copy of the standard at the worksite.
Permit-Required Confined Spaces–Early Warning Requirements No specific early-warning requirements for up-stream hazards. Early-warning requirement for up-stream hazards in sewer-type spaces.

General Outline of the Rule as outlined in 2007:

  1. 1926.1201—Introduction
  2. 1926.1202—Scope
  3. 1926.1203—Definitions
  4. 1926.1204—Worksite Evaluation, Information Exchange, and Coordination
  5. 1926.1205—Atmospheric Testing and Monitoring
  6. 1926.1206—Classification and Precautions
  7. 1926.1207—Reassessment
  8. 1926.1208—Permit-Required Confined Space
  9. 1926.1209—PRCS-Initial Tasks
  10. 1926.1210—PRCS-Preparing for Entry
  11. 1926.1211—During Entry
  12. 1926.1212—PRCS-Terminating Entry
  13. 1926.1213—PRCS-Rescue Criteria
  14. 1926.1214—PRCS-Entry Permits
  15. 1926.1215—Continuous System-PRCS
  16. 1926.1216—Controlled Atmosphere Confined Spaces—Requirements for Classification and Accident Prevention and Protection
  17. 1926.1217—Isolated-Hazard Confined Spaces—Requirements for Classification and Accident Prevention and Protection
  18. 1926.1218—Equipment
  19. 1926.1219—Records
Jeffrey Dalto

Jeffrey Dalto

Jeffrey Dalto is an Instructional Designer and the Senior Learning & Development Specialist at Convergence Training. He writes most of the articles on the Convergence Training blog. Jeff has worked in education/training for more than twenty years and in safety training for more than ten. You can follow Jeff at LinkedIn as well.

One thought on “New Confined Spaces in Construction Standard from OSHA: 1926 Subpart AA, 1926.1200

  1. This will change and make the contractors more responsible. Please keep me updated on any changes and updates on this proposed rule.

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