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Standard Interpretations - Table of Contents
• Standard Number: 1910.21(b); 1910.23(a)(2); 1910.23(c)(1); 1910.23(c)(3); 1910.27(b)(1); 1910.27(c)(3); 1910.27(c)(7); 1910.27(d)(2); 1910.27(d)(3); 1910.27(d)(4); 1910.132(a)

May 23, 2005

Mr. Stephen Hazelton, PE
TBI Tank Builders, Inc.
13400 Trinity Blvd.
P.O. Box 1527
Euless, Texas 76039

Dear Mr. Hazelton:

Thank you for your letter to the Occupational Safety and Health Administration's (OSHA) Regional Office, in Dallas, Texas, requesting a clarification of OSHA standards that may apply to steel water storage tanks that your company manufactures. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. We apologize for the delay in our response. Your paraphrased questions and our responses are provided below.

Question 1: Is the top of a tank considered to be a "roof" as applied to roofing work in the OSHA rules or is it considered a walking-working surface per Subpart D in 29 CFR 1910 standards?

Response: For purposes of OSHA's construction standards (29 CFR Part 1926), the top of a water storage tank would not be a "roof" but rather a "walking/working surface." See §1926.500(b) Definitions. The top of a water storage tank would be considered a "platform" for purposes of Subpart D of the General Industry standards (29 CFR Part 1910) depending on the frequency of employee use. OSHA has issued guidance on when an elevated working surface will be treated as a platform covered by the standard. See OSHA Instruction STD 1-1.13, "Fall Protection in General Industry 29 CFR 1910.23(c)(1), (c)(3), and 29 CFR 1910.132(a)" (April 16, 1984, copy enclosed).

We also call your attention to the fact that OSHA is engaged in a rulemaking to revise the requirements of Subparts D and I of 29 CFR Part 1910 (
55 Federal Register 13360, April 10, 1990; 68 Federal Register 23528, May 2, 2003). Under the proposed revisions, the top of a water tank where employees sometimes perform inspection or maintenance duties would fall within the definition of a "walking and working surface" as defined in the proposal, and fall protection would usually be required if the surface is more than four feet above an adjacent level. See proposed §1910.27(b)(1).

Question 2: Is fall protection required for people who go on top of the tank?

Response: Pursuant to §1910.23(c)(1), the open sides of platforms more than four feet above an adjacent floor or ground level must be guarded by a standard railing or the equivalent. If the top of a tank is not a "platform" under the analysis called for in OSHA's guidance document, the guardrail requirements of that standard would not apply. However, if perimeter guarding is not provided, fall protection in the form of personal protective equipment would likely be required by §1910.132(a).

Question 3: Is there a maximum slope that is considered acceptable as a walking surface? For example, on a dome shape is it acceptable to place a handrail at the edge and allow someone to walk there regardless of how steep it might be? Does it matter if a non-skid surface is applied?

Response: OSHA's current Subpart D does not include provisions concerning maximum acceptable slopes for walking and working surfaces. Under the proposed standard, the dome top of a water tank might fall within the definition of "ramp", in which case the maximum allowable slope would be 30 degrees from the horizontal. See proposed §1910.21(b)[definition of "ramp"] and proposed §1910.26(b)(1)(ii).

A steeply sloped walking or working surface increases the risk that an employee will slip and fall. Injury could also result if the employee slides into any perimeter guardrails or protrusions in the surface. Personal protective equipment as required by §1910.132 could take the form of shoes with slip resistant soles. Although not personal protective equipment within the meaning of §1910.132, a non-skid surface on the tank itself would provide additional protection, as would the installation of a handrail.

Question 4: If fall protection is used on a domed surface, does it just need to keep the person from falling off the edge or prevent them from sliding down the dome part?

Response: As indicated in our two previous answers, there would appear to be two hazards associated with walking or working on the top surface of a water storage tank — namely, falling off the tank and slipping and falling to the top surface of the tank. If both hazards are present, protection against each would likely be required.

Question 5: Does a flanged or hinged manway cover on the top of the tank need to comply with the "Safe Access Hatch" detail, D-6, in 1910.27? For example, does it need to be counterweighted? Does it need a lock-open device? (The manway may or may not have ladder under it. If a ladder is included, it is usually climbed from the top down, not from the bottom up, and any hasp, lock, or handle will always be on the top side of the manway.)

Response:No. The provisions under 1910.27 do not require that every hinged ladderway opening cover, such as a manway cover, comply with the "Safe Access Hatch", requirements contained in 1910.27(c)(7) and illustrated in Figure D-6. The design specifications contained in 1910.27(c)(7) apply only to hatch covers that are designed and provided with counterweights. In other words, if a hinged cover is designed with a counterweight, then the design specifications of this hatch cover must meet 1910.27(c)(7) requirements. In addition, OSHA standards do not require that manway covers be provided with lock-open devices.

Question 6: Figure D-8 of 1910.27 shows the basket guard hoop with the hoop attached to the rear of the ladder. Can hoops attach to the sides of the ladder, as in the standards published by American National Standards Institute (ANSI), ANSI 14.3-2002?

Response: Yes. OSHA considers such a deviation (i.e., attaching hoops to the side of the ladder instead of attaching to the rear of the ladder) from an OSHA standard to be "de minimis violation", that is, a violation of an existing OSHA standard which has no direct or immediate relationship to safety and health. De minimis violations of the OSHA standards result in no citation, no penalty, and no required abatement.

Question 7: Where a ladder has a step-through detail onto the top of the tank, is a swinging gate required at the ladder?

Response: OSHA standard at 1910.23(a)(2) requires that "Every ladderway floor opening or platform shall be guarded by a standard-railing with standard toeboard on all exposed sides (except at entrance to opening), with the passage through the railing either provided with a swinging gate or so offset that a person cannot directly walk into the opening." However, the proposed paragraph at 1910.28(b)(6) permits the use of movable guardrail sections such as gates, chains, and other means, which, when open, provide a means of access and, when closed, provide the guardrail protection that meets the proposed paragraphs 1910.28(b)(1) through (b)(5). An employer's compliance with the proposed rule, in lieu of compliance with an existing rule, is considered as a de minimis violation. As stated above, OSHA does not issue citations, impose penalties, or require correction of de minimis violations.

Question 8: Figure D-9 of 1910.27 shows a cage detail for short ladders at elevated locations. Which ladders does this apply to? Would it apply to the ladders shown in Figure D-10, if they were caged?

Response: The cage detail shown in Figure D-9 applies to all ladders that are required to be provided with cages, including the ladders shown in Figure D-10, if they were caged.

Question 9: Figure D-10 of 1910.27 shows the ladders offset at a platform, with two horizontal bars between each ladder. Are these bars required? Are these the "grab bars" mentioned in the paragraph below Figure D-10? (If so, they don't match the spacing requirement of the paragraph.)

Response: The two horizontal bars shown in Figure D-10 depict guardrails of an intermediate platform, and, therefore, are not required in connecting two sections of the fixed ladders. Additionally, these bars are not grab bars described under 1910.27(d)(4).

Question 10: We have seen an intermediate platform detail where the ladder goes through the platform (no offset) and a cover is closed over the ladder opening before continuing. The platform is large enough for the climber to step to the side of the ladder before closing the cover. Would this detail be considered to meet OSHA requirements?

Response: Paragraph 1910.27(d)(2) requires that each ladder section be offset from adjacent sections, and all landing platforms are equipped with standard railings and toeboards, so arranged as to give safe access to the ladder. Although paragraph (d)(2) requires that the ladders be offset from adjacent sections, the same offset provision does not apply to the landing platforms. Therefore, OSHA would deem situations such as you described in your letter (i.e., where the ladder goes through the platform (no offset) and a cover is closed over the ladder opening before continuing) to be in compliance with the OSHA provisions, as long as the platform is large enough to accommodate the ladders that are offset from each other, with a working space (without the space occupied by the ladders) of at least 24 inches in width and 30 inches in length and is provided with a ladderway opening cover and the platform's standard guard railings, meeting the Subpart D requirements.

Question 11: Is it acceptable for a caged ladder to come up through the floor of an intermediate platform, rather than beside it as shown in Figure D-10? (Assuming the platform size is increased to allow this.) If so, should the cage continue up 42 inches, or be terminated at the platform level?

Response: OSHA's Subpart D standards do not prohibit caged ladders going through the floor of an intermediate platform. Therefore, if a caged ladder comes up through the floor of an intermediated platform, rather than beside it as shown in Figure D-10, such a situation will not be in violation of OSHA standards, if all other provisions of 1910.27 are met. With respect to your question on extension of cages above the platforms, the proposed paragraph 1910.23(c)(15), in part, requires that "The cages and wells shall be continuous throughout the length of the fixed ladder, except for access, egress and other transfer points." In other words, if a fixed ladder with a cage is designed to go through a platform, the cage may be terminated at the platform level for the purposes of access and egress, provided the side rails of this ladder (which may be a through or a side-step ladder) extend 42 inches above the landing, as required under 1910.27(d)(3).

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at If you need further assistance, please contact the Office of General Industry Enforcement at (202) 693-1850.


Richard E. Fairfax, Director
Directorate of Enforcement Programs


Standard Interpretations - Table of Contents

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