Confined Space Entry Training

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Definition of a Hazardous Atmosphere – Flammable Gas, Vapor or Mist >10% LFL

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Hazardous atmosphere flammable gas vapor or mist greater than 10% LFL or LEL

 Blog Post #9 – In previous blog posts, we discussed how to identify confined spaces, and provided several examples of such spaces. Next we will examine the factors that determine whether or not each confined space identified at your workplace must be classified as a permit-required confined space, starting with a hazardous atmosphere that contains a flammable gas, vapor, or mist in excess of 10% of its lower flammable limit, or LFL.

 OSHA Definition of a Permit-required Confined Space

The Federal OSHA definition of a permit-required confined space for general industry can be found in 1910.146, paragraph B, titled definitions, and in 1926.1202, also titled definitions, for the construction industry. That is where OSHA lists the four types of hazards that require a confined space be classified as a permit required confined space. Those four types of hazards are:

  • The space contains an actual or potential hazardous atmosphere;

  • The space contains a material with the potential to engulf the entrant;

  • The space is configured to trap or asphyxiate the entrant; or;

  • The space contains some other recognized serious safety or health hazard.

 What is a Hazardous Atmosphere?

 The Federal OSHA definition for “hazardous atmosphere”, the first classification listed above, is also found in 1910.146, paragraph B, definitions, for general industry, and in 1926.1202, definitions, for the construction industry.

There are five different types, or classifications, of hazardous atmospheres, listed in these two OSHA definitions. Those classifications, which are nearly identical in the two standards, are:

 (1) – Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL);

 (2) – Airborne combustible dust at a concentration that meets or exceeds its LFL;

 (3) – Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent;

 (4) – Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in subpart G, Occupational Health and Environmental Control, or in subpart Z, Toxic and Hazardous Substances, of this part and which could result in employee exposure in excess of its dose or permissible exposure limit;

 (5) – Any other atmospheric condition that is immediately dangerous to life or health.

 The balance of this particular blog post focuses on the first category of a hazardous atmosphere listed above, which is a flammable gas, vapor, or mist greater than 10% of its lower flammable

Greater Than 10 Percent Lower Flammable Limit (LFL)

 OSHA includes this type hazard because they do not want employers to wait until conditions are ripe for a flash fire or explosion to occur inside of a confined space before taking precautionary measures. Atmospheric conditions inside a confined space that contain a low level of flammable gas, vapor, or mist could quickly change for the worse. Therefore, OSHA regulations classify a flammable gas, mist, or vapor present inside a confined space at levels over 10% of its LFL as a hazardous atmosphere. Once that level is reached inside a confined space, or if there is a reasonable probability that it will develop within the space during entry operations, that space must be classified as a permit-required confined space.

 Lower Flammable Limit (LFL) Explained

 So, what is LFL? It stands for Lower Flammable Limit. The LFL is the minimum amount of a particular flammable gas, vapor, or mist that must be present in the atmosphere to ignite and burn. If you introduce an extremely small amount of a flammable gas, vapor, or mist into the atmosphere of a confined space, it might not ignite when exposed to an ignition source (such as a spark or flame) because there is not enough of the material present to form a flammable mixture in the air. How much flammable gas, vapor, or mist is needed in the atmosphere for a fire or explosion to occur? That depends on the gas, vapor, or mist present inside either space, as they all have a different LFL.

 What is LEL?

Be aware the term “LFL” is also referred to as “LEL”, or Lower Explosive Limit. The terms LFL and LEL are basically interchangeable. While OSHA uses LFL in their confined space standards, LEL is commonly used by many gas detection equipment manufacturers, as well as in many written confined space entry programs. Also, I may on occasion use the term LEL throughout future blog posts.

 LFLs of Common Flammable Gasses

The LELs of a few common combustible materials are listed in the chart below. An LEL is expressed as a percentage of the atmosphere within the confined space that is comprised of a particular combustible gas, vapor, or mist. For example, the LEL of Methane gas, with the chemical identifier of CH4, is 5% of the atmosphere at any given point. As you can see, the LELs of various gases differ quite a bit. 

Upper and lower flammable limits of common gasses

What does UFL mean?

Note that each of the combustible materials listed in the chart also have their own UFL, or Upper Flammable Limit (expressed in the chart as an UEL). If a flammable gas, vapor, or mist is present in the atmosphere in quantities greater than its UFL, it will not ignite and burn. I bring up this term because while OSHA does not regulate UFLs, they do come into play when we discuss gas detection equipment in later blog posts.

Flammability Characteristics of Methane Gas

As mentioned earlier, the LFL of Methane gas is 5%. So, if Methane gas is present in a confined space, but it does not make up at least 5% of the atmosphere at any point within the space, there will be no flash fire or explosion if there is a spark or other source of ignition. And the upper flammable limit, or UFL, of Methane gas is 15%; So, a confined space containing higher levels of Methane would not burn or explode either. However, if the amount of Methane gas increases or decreases to fall somewhere between its LFL and UFL at any point inside a confined space and there is any source of ignition in that same area, a fire or explosion will occur.

Since Methane gas has an LFL of 5% of the atmosphere, a hazardous atmosphere as defined by OSHA would be present inside a confined space if the amount of Methane gas in the atmosphere exceeds 10% of that level. The presence of that level of Methane gas, which equates to just 0.5% of the total atmosphere, means the space would have to be classified as a permit-required confined space.

Other Hazards Associated with Methane Gas

Before moving on, let’s take a moment to discuss Methane gas, or CH4, a little more, as this is a hazardous gas commonly found in a variety of confined spaces. Methane is a colorless, tasteless gas that has no odor, so its presence cannot be detected by your senses alone. But too much Methane gas inside of a confined space creates not only a potentially flammable atmosphere, as previously discussed, it can also displace oxygen in the space, creating a deficiency of oxygen for an entrant to breathe. Fortunately, while Methane is a highly flammable gas that can also displace oxygen, it is one of the few flammable gases that is not toxic.

Where is Methane Gas Commonly Found?

Methane is created when organic matter decomposes. Therefore, it is commonly found in potentially harmful quantities within confined spaces such as sewers and related facilities, manure pits, and in silos that have held grain or similar materials that has rotted. Methane is also commonly found in confined spaces such as underground utility vaults, especially those located near landfills (the rotting trash creates Methane). Therefore, these spaces are typically classified as permit-required confined spaces.

More Examples of Confined Spaces With Potentially Flammable Atmospheres

Other examples of confined spaces with a reasonable potential to contain an atmosphere containing a flammable gas, vapor, or mist above 10% of its LFL include pipelines, tanks and other vessels that have contained fuels or other flammable or combustible materials, even when they have been emptied of their contents. Also, confined spaces where work processes such as cutting with an oxy-acetylene torch or painting with flammable paints and solvents is taking place inside could potentially contain a hazardous atmosphere. And confined spaces such as vaults or tunnels in which there are leaking valves or piping used to transport flammable gas could also contain a hazardous atmosphere. As such, each of these spaces would also likely be classified as a permit-required confined space.

So, in review, any confined space with an actual flammable gas, vapor, or mist present at levels greater than 10 percent of its lower flammable limit, or LFL, is considered to have a hazardous atmosphere. And that means the space must be classified as a permit-required confined space. The same is true for any confined space in which that level of a flammable atmosphere could reasonably be expected to develop during entry operations. You may also hear the term LEL, which stands for lower explosive level, being used to describe a hazardous flammable atmosphere inside a confined space, as that term is synonymous with LFL.

In our next blog post (#10), we will examine the second criteria of a hazardous atmosphere that could be present inside of a confined space (combustible dust). In the meantime, please provide your feedback and questions to this blog post in the comments section below. And as always, I urge you to share a link to this confined space training blog post with anyone in your network who could benefit from this information. Thanks – Curtis

Difference Between Permit Required Confined Spaces and Non-Permit Required Confined Spaces

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Difference between permit-required confined space and non-permit-required confined space

 Blog Post #8 – In this post to The Confined Space Training Blog, we will discuss the differences between a confined space that meets the Federal OSHA definition of a permit-required confined space versus one that can be classified as a non-permit required confined space.

Why make the distinction between permit and non-permit required confined spaces? Because entry into that space classified as a permit-required confined space is only allowed under an entry program meeting all pertinent requirements of the OSHA permit-required confined space entry standard. However, confined spaces that do not meet the OSHA definition of a permit space, which are called non-permit required confined spaces, may be entered without having to follow those additional precautions.

Criteria of a Permit-required Confined Space per the OSHA Definition

According to OSHA, a space is classified as a permit-required confined space if it meets one or more of the following characteristics:

  1. The space contains an actual or potential hazardous atmosphere;

  2. The space contains a material with the potential to engulf the entrant;

  3. The space is configured to trap or asphyxiate the entrant; or;

  4. The space contains some other recognized serious safety or health hazard.

We will break down each one of these four characteristics in subsequent blog posts. But for now, just be aware that it only takes one of these characteristics to be present, or reasonably expected to be present, for a confined space to be classified as a permit required confined space. Also, a permit-required confined space may contain two or more of these characteristics, and they all need to be identified so the hazards can be adequately addressed before entry operations begin.

What is a Non-permit Required Confined Space?

But what if the confined space does not meet any one of the four characteristics listed above? Then it could be classified as a non-permit space. According to the OSHA definitions in 1910.146 and in 1926 subpart AA, a non-permit required confined space is “a space that meets the definition of a confined space, but does not meet the requirements for a permit-required confined space, as outlined by the OSHA standard.”

When Re-evaluation of a Non-permit Space is Necessary

Keep in mind, however, that an employer must re-evaluate a non-permit required confined space if there are any changes to the use or configuration of that space that might increase the hazards to entrants, or if there is some indication that the initial evaluation of the space may not have been adequate. And if an actual or potential hazard is identified, the space must be reclassified as a permit-required confined space at that time.

For example, if a stainless-steel process tank is newly installed and has never held any material, and it has no agitators inside the tank or fill lines attached, it could be classified as a non-permit required confined space because it does not contain any health or safety hazards. However, if an employee needs to enter the tank to conduct an inspection and must decontaminate the inside of the tank before exiting by wiping it with isopropyl alcohol, which is flammable and toxic, the tank must be temporarily reclassified as a permit-required confined space during the performance of this task.

Reclassification of a Permit-required Confined Space to a Non-permit Confined Space

Last but not least, there are some opportunities where an employer who needs to enter into a permit-required confined space can implement steps to isolate the space from its hazards, allowing it to be temporarily reclassified as a non-permit confined space for as long as those hazards remain eliminated. More on that subject in a later blog post (#19).

Why it is Important to Properly Classify All Confined Spaces

Again, employers need to evaluate each confined space at their worksites to distinguish if it must be classified as a permit-required confined space, which requires implementation of a full permit-required confined space entry program, or if it can be classified as a non-permit required confined space. In the latter case, the space does not have to be identified with a warning sign, no permit is required to be filled out prior to entering the space, and no precautions listed in the OSHA permit-required confined space standards need be taken unless changes to the space or entry operations present an actual or potential hazard.

In our next blog post (#9), we will start examining what constitutes a hazardous atmosphere inside of a confined space. In the meantime, please provide your feedback and questions to this blog post in the comments section below. And as always, I urge you to share a link to this blog post with anyone in your network who could benefit from this information. Thanks – Curtis

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OSHA Requirement for a Competent Person to Identify Permit Required Confined Spaces

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Confined Space Competent Person

Post #5 – The success of an organization’s confined space entry program is ultimately predicated on having a competent person with the ability to identify and evaluate the confined spaces at their work sites to determine whether or not they meet the OSHA definition of a permit-required confined space. And that takes a person with sufficient training and experience to do the job right. But exactly whose job is it to identify and evaluate confined spaces?

Here’s what the OSHA confined space regulations say about that.

OSHA Requirements to Evaluate Confined Spaces

The first paragraphs from the general requirements sections of the OSHA confined space entry standards for general industry and construction, respectively, are listed below:

GENERAL INDUSTRY

1910.146(c)(1) – The employer shall evaluate the workplace to determine if any spaces are permit-required confined spaces.

CONSTRUCTION

1926.1203(a) – Before it begins work at a worksite, each employer must ensure that a competent person identifies all confined spaces in which one or more of the employees it directs may work, and identifies each space that is a permit space, through consideration and evaluation of the elements of that space, including testing as necessary.

As you see, both of these performance-based confined space standards place the onus on employers, either individually or through a designated Competent Person, to evaluate their workplaces to determine if any confined spaces are present. Then, they must determine if any of those confined spaces are to be categorized as a permit required confined space, or alternatively, as a non-permit-required confined space.

Special Qualifications or Certifications Needed to  Evaluate Confined Spaces?

While OSHA requires employers to ensure the confined spaces at their worksites are identified and evaluated, their standards do NOT require the completion of any specific training class or “competent person certification” for confined spaces for the person conducting the evaluations. Instead, an OSHA compliance officer would simply speak with whomever the employer has appointed as their competent person to perform the confined space evaluations, and determine if they seem to have adequate experience, training certification, and knowledge needed to do the job competently.

Duties of the Competent Person Evaluating Confined Spaces

The competent person who is designated to evaluate the confined spaces at a worksite to determine whether or not they are permit spaces must be capable of effectively performing the following three tasks for the worksite in question:

  • Identify all confined spaces at the worksite after consideration of all facets of the OSHA definition of a confined space;
  • Determine if each confined space identified at the site will be categorized as a permit-required confined space, or as a non-permit confined space;
  • When conditions demand, re-evaluate (and possible reclassify) a non-permit confined space, should the configuration of that space change in a manner that could cause it to become a permit-required confined space (especially true during progression of the construction process when building a confined space such as a tank). Re-evaluation of a non-permit required confined space must also be performed every time there is a work process or activity taking place inside of, or near, any non-permit confined space which could potentially introduce new hazards that require the non-permit space be reclassified as a permit-required confined space.

In many cases, an employer also will have the person designated as their competent person for confined space identification to serve as the entry supervisor for their confined space entry crew. However, doing so is not a strict requirement of the confined space standards, as those two roles could be filled by different personnel.

OSHA Documentation Requirements for Confined Space Evaluations

In case you were wondering, there is no requirement in the federal OSHA confined space entry standards requiring the employer to document their confined space evaluations; however, some employers may choose to do so anyway.

Identifying Permit-Required Confined Spaces at Multi-employer Worksites

OSHA gives employers working at a multi-employer job-site such as but not limited to construction sites the option to collaborate on identifying permit spaces at a worksite, by agreeing to use one designated competent person to perform the initial surveys. Or they can choose to use their own designated competent person to perform the surveys. But either way, each employer who has an employee who will enter into a confined space is ultimately responsible for compliance with the requirements of the OSHA confined space entry standards, and must therefore utilize due diligent before deciding to count on another employer’s competent person to perform the evaluations.

Designation of a Person Competent to Identify Permit-required Confined Spaces

Obviously, the wide variety in types of confined spaces and the assortment of potential hazards inside of those spaces will vary greatly from site to site. So, a competent person with training and experience in dealing with only one specific type of confined space may be capable of evaluating the spaces in a worksite if it only contains the same types of spaces with which they are already familiar. But that same person may or may not be suitable for evaluating the confined spaces of a type they have not experienced before. Only the employer can decide, based upon his or her knowledge of, and experience with permit required confined spaces, who is adequately prepared and able to be designated as being their competent person responsible for identifying permit-required confined spaces at the workplace.

Coming up in the next blog post (#6); we will start a deep dive into understanding the OSHA definition of a confined space.

Final Note: Thanks for reading the blog. Please help spread the word about our confined space entry training blog by sending a link to the blog to others in your network who could benefit from this information. Thanks – Curtis

Understanding the Scope and Application of OSHA’s Various Permit Required Confined Space Entry Standards

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Which OSHA Confined Space Entry Standards Apply

Post #4 – As mentioned in an earlier blog post (#2), OSHA has three different sets of confined space entry standards; one applies to construction work, and another applies to general industry work. OSHA also have a standard that applies to confined space work conducted in the Maritime industry, but that standard will not be discussed in this blog post.

It is imperative that you understand which of the OSHA standards apply to your particular confined space entry operations, and conversely, which one does not, as the requirements of each standard differ. And the way to make sure you understand is to refer to the sections that list the scope and the application for each of the OSHA confined space entry permit requirements.

Scope of the OSHA Confined Space Entry Standards Applicable to General Industry

1910.146(a) lays out the scope of the OSHA permit-required confined space entry standards for general industry workplaces. It states:

“This section contains requirements for practices and procedures to protect employees in general industry from the hazards of entry into permit-required confined spaces. This section does not apply to agriculture, to construction, or to shipyard employment (parts 1928, 1926, and 1915 of this chapter, respectively).”

To reiterate information provided in post #2, general industry work typically consists of activities performed during the manufacturing of goods or products, including those at chemical plants and refining operations. General industry work also includes most general maintenance activities. Service industries such as telephone and cable companies, restaurants, coffee shops and bakeries are also covered by the OSHA 1910.146 general industry standards for confined space entry, as are warehousing and logistics operations and the healthcare industry. 1910.146 would even apply to work involving entry operations at establishments such as bowling allies and amusement parks.

Scope of the OSHA Confined Space Entry Standards Applicable to Construction

For the construction industry, 29 CFR 1926, paragraph 1201(a) explains the scope of the confined spaces in construction standards. This paragraph states the following:

“This standard sets forth requirements for practices and procedures to protect employees engaged in construction activities at a worksite with one or more confined spaces.”

According to 1910.12(b), work regulated under 1926 subpart AA construction standards applies only to confined space entry operations related to construction, alterations, and/or repairs, which include painting and decorating. This would include, but is certainly not limited to, confined space entry work involved in the construction of a brand-new structure, major renovation or repair of all or part of an existing structure, repainting portions or all of a structure, and demolition work. 

Which Confined Space Standard Takes Precedence?

Here is the tricky part; while the 1926 subpart AA confined spaces in construction standard does not apply to general industry work, that standard does apply to construction work conducted inside of a confined space that happens to be located at a general industry worksite.

Consider the following hypothetical of how entry into a tank, which as we will see in an upcoming blog post is usually considered a confined space, could feasibly be regulated by both the OSHA confined space entry standards for construction and also the confined space standards for general industry, switching back-and-forth over the course of time. Notice how the determination depends on the work activities that are taking place, and not the location.

  1. A large tank is fabricated in the shop at a manufacturing company, including having a protective lining sprayed onto the interior tank surfaces by a worker: this work is regulated under 146 General Industry requirements for confined space entry.
  2. The tank is erected at a chemical plant expansion project, where workers enter the tank to install fill lines and drain pipes: this work is regulated under 1926 Subpart AA Construction requirements for confined space entry.
  3. After the chemical plant is up and running in normal production, entry is made into the tank once a year to conduct an inspection of the protective lining on the interior surfaces of the tank to determine its general condition: this preventive maintenance work is regulated under 146 General Industry requirements for confined space entry.
  4. After an annual inspection discovers damage to the lining caused when the tank was previously struck by a forklift, a lining crew enters the tank to blast out the old lining and reapply a new tank lining: this repair work is regulated under 1926 Subpart AA Construction requirements for confined space entry.
  5. Subsequent annual entries are made to conduct inspections of the interior lining to determine its general condition: this preventive maintenance work is regulated under 146 General Industry requirements for confined space entry.
  6. After 30 years of use, the tank has been deemed obsolete, and is scheduled to be demolished. A crew enters the tank to cut loose interior braces and baffles as part of the tank demolition process; this demolition work is regulated under 1926 Subpart AA Construction requirements for confined space entry.

As the previous set of scenarios demonstrate, the over-riding factor to determine which set of OSHA confined space entry permit requirements apply to a given situation is usually the type of work (general industry or construction) being performed inside the confined space, as opposed to the location where the confined space work happens to be taking place.

Application – Workplaces Where OSHA Confined Space Standards Do Not Apply

I will wrap up this blog post by touching certain employers to whom the OSHA confined space entry permit requirements do not apply. The OSH Act of 1970, which establishes coverage of federal OSHA standards, was originally written to apply only to private sector employers in the U.S. and its territories. That means public employers like state and local government agencies (e.g.: municipalities and counties) are not regulated by the OSHA standards, including those for confined space entry operations, unless they happen to be located in one of the states or territories operating under a State Plan OSHA program, as explained in a blog post #2.

Also exempt from coverage by the OSH Act, and therefore exempt from the federal OSHA confined space entry standards, are workplaces for which other federal agencies have laws that regulate employee safety in certain operations. For example, entry into underground mines, which logically seem to be confined spaces, are actually covered by the Mine Safety and Health Administration (MSHA) regulations, and are therefore exempt from OSHA standards for confined space entry. And construction work conducted at worksites overseen by the U.S. Army Corp of Engineers must follow the EM-385-1-1 requirements for confined space entry.

Do Federal Confined Space Entry Requirements Apply to the Feds?

One last interesting factoid; the OSH Act originally did not apply to Federal agencies, meaning federal employers were not required by Congress to follow OSHA’s confined space entry standards; in fact, not even OSHA was required to follow their own confined space entry regulations! However, because of an executive order issued in 1980, federal agencies do now have limited coverage by OSHA standards, and must therefore comply with applicable OSHA confined space entry requirements (and all other applicable OSHA standards) during their entry operations.

Additional Information and Training on Confined Spaces

Hopefully this blog post helps clarify which OSHA confined space entry requirements apply to work being conducted at your site. Or, it may make you realize OSHA lacks jurisdiction over confined space entry operations at your worksite, and that you must figure out what alternate set of regulations may apply. You can learn more about this and other topics by taking one of the online confined space training courses available on our website.

In the next blog post (#5), we will address exactly who is responsible for making sure all permit-required confined spaces at the worksite are properly identified.

Final Note: Thanks for reading the blog. Please help spread the word about our confined space entry training blog by sending a link to the blog ( https://confinedspacetraining.net/confined-space-training-blog/ ) to others in your network who could benefit from this information.

Thanks, – Curtis

Key References Needed to Understand the OSHA Confined Space Entry Standards

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OSHA confined space standards preamble in federal register and letters of interpretation plus CSE FAQs

Post #3 – In the previous post to the confined space training blog, I identified various OSHA standards governing confined space entry work for construction and general industry work (as well as the maritime industry). However, many of the terms used in these confined space standards are not well defined, if defined at all, whereas other parts of these standards are vague and seem to be open to interpretation. These issues often lead to uncertainty about whether or not you are in compliance with the requirements of the OSHA confined space entry standard.

Fortunately, OSHA provides many key documents that expand on their various confined space entry requirements, offering much needed information that helps clarify their standards. (Note: from this point forward in my blog posts, I will focus primarily on the OSHA confined space entry standard for general industry and construction, and not on the OSHA maritime regulations for confined spaces). The following is a recap of some of the more helpful OSHA documents.

Appendices to the OSHA 1910 Permit-required Confined Space Entry Standards

The permit-required confined space entry standard for general industry has several appendices that provide useful information when developing or evaluating your confined space entry program. Below is a listing of those appendices:

1910.146 App A – Permit-required Confined Space Decision Flow Chart

1910.146 App B – Procedures for Atmospheric Testing

1910.146 App C – Examples of Permit-required Confined Space Programs

1910.146 App D – Confined Space Pre-Entry Check List

1910.146 App E – Sewer System Entry

1910.146 App F – Non-Mandatory Appendix F — Rescue Team or Rescue Service Evaluation Criteria

Currently, the Confined Spaces in Construction standards have no appendices. However, those provided with the general industry standard will also prove to be informative for people in the construction industry when setting up their permit-required confined space entry programs.

Federal Register Preambles to The OSHA Confined Space Entry Standard

When OSHA sets out to create a new or revised standard, they must first publish it in the form of a proposed rule in the Federal Register. This is done so interested parties can review the proposed standard and provide written or verbal feedback during a mandatory public comment period. Then, OSHA will review these comments for consideration when they formulate a final rule. When OSHA publishes the final rule, again in the Federal Register, that document includes not only the text of the new standard, but also a very valuable section of the preamble titled “Summary and Explanation of the Standard” (usually in section III). The preambles to the final confined space entry rules for construction and general industry are available for access at https://www.osha.gov/laws-regs/preambles.

The “Summary and Explanation of the Standard” section of the preambles lists the verbiage of each paragraph of the proposed rule as it was originally written, comments, if any, submitted about each proposed paragraph gathered during the public comments period for the new or revised rule, and OSHA’s responses, if any, to those comments. The preamble also includes OSHA’s final reasoning and determination regarding any revisions to the final language of each paragraph of the final rule. It is in OSHA’s responses to those public comments that you can glean very valuable information about how OSHA interprets and/or plans to enforce each paragraph of a new or revised standard.

The preamble to the OSHA 1910 general industry permit-required confined space entry standard was published in Federal Register volume 58, number 9 on January 14, 1993, beginning on page 4462. The preamble to the 1926 Subpart AA confined spaces in construction rule was published in Federal Register volume 80, No. 85 on Monday, May 4, 2015. I will point out helpful information appearing in specific portions of these documents in many future blog posts.

OSHA Compliance Directive (CPL) for 1910.146 Permit-required Confined Space Entry Standard

OSHA occasionally issues a compliance directive (CPL) or standard directive (STD) on some of their more complex standards or policies. These directives are primarily intended to be used as instruments for OSHA compliance officers and directors to refer to during inspections, helping ensure uniform understanding and enforcement of the associated standard or policy.

On May 5th, 1995, OSHA issued Instruction CPL 2.100, which is a compliance directive on the subject of the “Application of the Permit-Required Confined Spaces (PRCS) Standard, 29 CFR 1910.146”. OSHA updated that particular CPL on September 1 of 2015. There is a wealth of information in the directive that employers and other interested persons can use to better understand how OSHA interprets and enforces the 1910.146 standard. And much of that same information can also be applied to the 1926 Subpart AA construction standard.

Letters of Interpretation – OSHA Confined Space Entry Standards for General Industry and Construction

OSHA receives thousands of inquiries about their various standards every year, with several of those posing questions about the OSHA confined space entry standards for construction or for general industry. In many cases, OSHA formally responds to those inquiries via a “letter of interpretation”, often referred to as a LOI. Because these letters of interpretation are considered public records, OSHA makes them available to the general public (like you and me) for review on their website.

The OSHA letters of interpretation for the 1910.146 general industry standards for permit-required confined space entry and for the 1926 Subpart AA confined spaces in construction standard are all accessed through OSHA’s LOI search page. Be aware that OSHA letters of interpretation for their confined space standards are only intended to apply to the specific circumstances discussed in that letter, and that they should not be applied to other circumstances, no matter how similar. Also, OSHA letters of interpretation are occasionally withdrawn because OSHA changed their mind; these letters will be marked as withdrawn, but are still available for reference as archived material.

Frequently Asked Questions and Answers (FAQs) for OSHA Confined Space Entry in Construction Standards

Anticipating questions about their (then) newly-promulgated 1926 Subpart AA confined spaces in construction standard, OSHA published on their website a “Frequently Asked Questions” (FAQ) page about that standard. At the time of this post, there were more than 70 questions and associated answers available on the OSHA confined spaces in construction FAQ page. Readers can get a much better understanding of the OSHA confined space entry requirements not only for the construction industry from these FAQs, but also for many of the similar confined space requirements for general industry workplaces.

OSHA Confined Space Advisor

OSHA developed a resource titled “Confined Space Advisor” on their website. This online tool is essentially a decision flow chart that asks the user questions, and based on their answers, guides them through the various steps of identifying permit-required confined spaces, and subsequently, developing and implementing a permit-required confined space entry program.

The OSHA confined space advisor e-tool is pretty basic in its coverage, and in my opinion, does not adequately answer questions about all confined space entry standards and terms that are vague. However, it does, on occasion, clearly indicates how OSHA defines or interprets a few of them; in fact, there are a couple of instances where I incorporate information taken from the online advisor in the online confined space training courses available on our website.

State OSHA Standards and Requirements for Confined Space Entry

Last but not least; it would be remiss of me not to mention that several states and US territories have opted to form their own State Plan OSHA program, covering most private and public employers in some of these states, and just the public employers in other states. All of these State Plan OSHA programs are required to either adopt the equivalent of the Federal OSHA regulations, or develop and publish their own state regulations that meet or exceed the protections offered in the associated Federal OSHA standards.

In most cases, the Federal OSHA standards for confined space entry in construction and for general industry were adopted verbatim by the various State Plan programs (reference all State Plan program rules at https://www.osha.gov/stateplans/statestandards). However, a few of the state programs created similar standards with a few slight tweaks to reflect other state-specific standards referenced within their rules. For example, the confined space entry standards promulgated by the state of California State Plan program (often referred to as Cal-OSHA) are nearly the same as those published by Federal OSHA, although CA did utilize a different numbering system when they codified their standards. But in the definitions for a “hazardous atmosphere”, which is one of the triggers for classifying a confined space as “permit required”, the CA state rule is slightly different (see both definitions below):

DEFINITION (for both Federal and Cal-OSHA confined space entry standards) –

“Hazardous atmosphere means an atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit space), injury, or acute illness from one or more of the following causes:

FEDERAL OSHA –

(4) Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in subpart D of this part (Occupational Health and Environmental Control), or in subpart Z of this part (Toxic and Hazardous Substances), and which could result in employee exposure in excess of its dose or permissible exposure limit;

Cal-OSHA –

(4) Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in Article 4 of the Construction Safety Orders and Group 16 of the General Industry Safety Orders;”

This slight difference in language can make a huge difference in how these two varying standards are applied. For example, the permissible exposure limit (PEL) for carbon monoxide (CO) incorporated by reference in the 1910 Federal OSHA standard is 50 parts per million (PPM). However, the PEL for CO incorporated by reference in the Cal-OSHA state standard is only 25 PPM. This represents a big variance between the Federal and Cal-OSHA thresholds for when a confined space containing CO is considered to contain a hazardous atmosphere, and therefore classified as a permit-required confined space.

OSHA Confined Space Training Resources

In closing, remember that it is important to be thoroughly familiar with the language contained in the actual OSHA confined space entry standards that apply to your operations. However, there are also many other important OSHA documents available that provide a wealth of information and guidance on how these confined space standards should be interpreted, implemented, and ultimately enforced in the workplace. Links to the resources outlined above, as well as many other valuable resources for confined space entry programs, are available via the course materials tabs associated with the online confined space entry training certification courses for entry supervisors and the competent person offered on our website.

Final Note: Please help spread the word about our confined space entry training blog. Send a link to this blog post to others in your network who could benefit from this information. Thanks, Curtis