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 https://www.osha.gov.

July 25, 2019

Mr. Scott Day
SafeDay, Inc.
727 Walkertown-Guthrie Road
Winston-Salem, North Carolina 27101

Dear Mr. Day:

Thank you for your inquiry to the Occupational Safety and Health Administration (OSHA). Your inquiry has been referred to OSHA’s Directorate of Enforcement Programs for answers to several questions related to OSHA’s Respirable Crystalline Silica (RCS) standard for construction, 29 CFR 1926.1153. This letter constitutes OSHA's interpretation only of the requirements discussed, and may not be applicable to any question not delineated within your original correspondence. Your paraphrased questions and our responses are below.

Question 1: Does OSHA’s RCS construction standard apply to certain tasks that appear to be excluded from coverage in the OSHA Fact Sheet, FS 3681 - 2016 and OSHA’s Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for Construction, 3902-07R - 2017, although the tasks are not specifically identified as being excluded from coverage in the regulatory text? These tasks include: mixing concrete for post holes; mixing mortar; pouring concrete footers, slab foundation, and foundation walls; and removing concrete formwork.

Response: OSHA’s RCS construction standard applies to all employee exposures to respirable crystalline silica in construction work, except where the exposures will remain below the action level (AL) of 25 micrograms per cubic meter (µg/m3) as an 8-hour time-weighted average (TWA) under any foreseeable conditions (see 29 CFR 1926.1153(a)). OSHA has identified the following tasks that are likely to be outside the scope of the RCS construction standard because they typically generate exposures below the AL of 25 µg/m3 as an 8-hour TWA under all foreseeable conditions when they are performed in isolation from other silica-generating tasks: mixing small amounts of mortar; mixing small amounts of concrete; mixing bagged drywall compound that contains crystalline silica only as a trace contaminant; mixing bagged exterior insulation finishing system base and finish coat; removing concrete formwork; using block or tile splitters; and using manual (i.e., non-powered) chisels, shears, and utility knives. In addition, tasks where employees are working with silica-containing products that are, and are intended to be, handled while wet, are likely to generate exposures below the AL under any foreseeable conditions. Examples of such tasks include finishing and hand wiping block walls to remove excess wet mortar, pouring concrete, and grouting floor and wall tiles.

Employers should be aware that tasks like mixing mortar or concrete can foreseeably result in exposures at or above the RCS AL, depending on factors such as the duration the task is performed, location, and the method used for mixing. For example, breaking open bags of mortar and dumping them into mechanical mixers for an extended period during a work shift could foreseeably result in employee exposures that reach or exceed the AL. In addition, large-scale mortar mixing operations in which silos are used to fill large mixers can also result in exposures at or above the AL.

Further, in 2017, OSHA revised its Fact Sheet, FS 3681 - 2016, to avoid any potential confusion regarding coverage of mortar mixing under the RCS construction standard. A copy of this revised fact sheet, FS 3681 - 2017, is enclosed.

Note that during an inspection, an OSHA compliance safety and health officer might conduct sampling when he/she has reason to believe that exposures may reach or exceed the AL. The persistent presence of visible dust, an equipment malfunction, or another unexpected event that could affect employee exposures may indicate that it is no longer reasonable to expect employee exposures to remain below the AL.

Question 2: Does the RCS construction standard apply to tasks like drilling holes in silica-containing materials with handheld drills or certain activities like manual or mechanical mixing of mortar or concrete if they are performed for short durations of time, e.g., 15 minutes or less per day?

Response: The RCS construction standard does not include a specific exemption for RCS-generating tasks that involve only short-term exposures (e.g., tasks with exposures for 15 minutes a day or less). We recommend that you review the Frequently Asked Questions ("FAQs") for Occupational Exposure to Respirable Crystalline Silica, 29 CFR 1926.1153, in the Construction Industry on OSHA’s website,1 specifically FAQ 2, which provides a detailed explanation for coverage under the standard of employees who perform silica-generating tasks for only 15 minutes or less a day.

Question 3: The first entry in Table 1 of OSHA’s RCS construction standard is titled “(i) Stationary masonry saws.” The term “masonry” is not defined in the regulatory text. Would users of stationary tile saws that involve wet cutting methods, regardless of whether water is “fed” to the blade or if the blade simply runs partially submerged in water, be in compliance with the standard while using such saws when cutting porcelain, natural stone, and ceramic tile?

Response: OSHA considers stationary tile saws used to cut silica-containing masonry materials such as porcelain, stone, and tile to be stationary masonry saws under the RCS construction standard (see Chapter IV of OSHA's Final Economic Analysis and Final Regulatory Flexibility Analysis, for additional description of stationary masonry saws at 5.7.1, page IV-831). A stationary masonry saw equipped with an integrated water delivery system that continuously feeds water to the blade meets the requirements for Table 1 in the RCS standard when the control is fully and properly implemented. However, a stationary masonry saw that partially submerges the blade in water, but does not continuously feed water to the blade, does not meet Table 1 requirements.

Question 4: When a masonry/stone/concrete/tile saw blade, which is not a grinding wheel, is mounted on a small handheld electric motor-driven tool (often referred to as a “handheld grinder”) to cut, but not grind, tile/masonry/stone/concrete, would the tool be considered a “handheld power saw (any blade diameter)” as described in Table 1, 29 CFR 1926.1153(c)(1)(ii), or would it be considered a “handheld grinder for uses other than mortar removal” as described in Table 1, 29 CFR 1926.1153(c)(1)(xii), even though it has been effectively turned into a saw? Grinding wheels typically remove material with the broad face of the wheel and cutting blades typically remove material with the narrow edge of the blade just like larger stationary and handheld masonry saw blades do. Please clarify.

Response: The RCS standard covers handheld grinders for uses other than mortar removal at 29 CFR 1926.1153(c)(1)(xii) in Table 1. When manufacturers’ specifications permit handheld grinders to be fitted with cutting blades or cutting attachments, OSHA considers them to be handheld power saws under the RCS standard, and they are thus covered under the 29 CFR 1926.1153(c)(1)(ii) entry in Table 1 for handheld power saws (with any blade diameter). Note that the mounting of saw blades on to a handheld grinder, when such substitution is prohibited by the grinder manufacturer or not in accordance with the manufacturer’s specifications, can lead to loss of control of the tool and the blade, which can result in injury, including lacerations and amputations. Any such unapproved substitutions may potentially be subject to citation under Section 5(a)(1), General Duty Clause, of the Occupational Safety and Health Act of 1970.

Question 5: Does Table 1, 29 CFR 1926.1153(c)(1)(xvii), allow use of open cab equipment along with application of water or dust suppressants to protect equipment operators, who use heavy equipment and utility vehicles to abrade or fracture silica containing materials, including for demolition?

Response: No. Table 1, 29 CFR 1926.1153(c)(1)(xvii), requires the use of an enclosed cab whenever heavy equipment and utility vehicles are used to abrade or fracture silica-containing materials or during demolition activities involving silica-containing materials. An employer would not be in compliance with Table 1 if the operator performs these tasks from an open cab, even while water or dust suppressants are applied outside the cab. The cab must also meet the requirements specified at 29 CFR 1926.1153(c)(2)(iii) .

Question 6: 29 CFR 1926.1153(f)(1), Housekeeping, states, “The employer shall not allow dry sweeping or dry brushing where such activity could contribute to employee exposure to respirable crystalline silica unless wet sweeping, high efficiency particulate air (HEPA) filtered vacuuming or other methods that minimize the likelihood of exposure are not feasible.” Would the use of oil-based or wax-based sweeping compounds (dust down) be considered an “other method” when used in sufficient quantity while sweeping to control visible dust emissions? Would the use of a non-HEPA filtered vacuum for housekeeping be considered an “other method”?

Response: The proper use of commercially available dust-suppression sweeping compounds in accordance with the manufacturer’s instructions is an “other method” that minimizes the likelihood of exposure for purposes of paragraph (f)(1). Thus, sweeping with oil-based or wax-based sweeping compounds is permitted under paragraph (f)(1). OSHA has also provided additional clarification on the use of dust-suppression sweeping compounds in its letter to Mr. Michael Peelish, November 2, 2018.

Generally, the use of a non-HEPA filtered vacuum for housekeeping would not be considered an “other method” under paragraph (f)(1) because it does not minimize the likelihood of exposure. OSHA discourages cleaning with non-HEPA-filtered vacuums because when vacuums without HEPA filtration are used, respirable particles are discharged through the vacuum’s exhaust into the immediate work area and can contribute to employee exposures. Note also that several Table 1 tasks explicitly require the use of HEPA-filtered vacuums during associated cleaning activities in order to comply with the Table. See 29 CFR 1926.1153(c)(1)(vii) (handheld and stand-mounted drills), (viii) (dowel drilling rigs for concrete), (xiii) (walk-behind milling machines and floor grinders); see also 81 FR at 16735-36.

Question 7: Can the employer be cited if it makes medical surveillance available, in accordance with 29 CFR 1926.1153(f)(1), to an employee who is already employed as of the effective date of the RCS standard, and the employee subsequently refuses to participate in medical surveillance? Can the employee continue to be employed in silica exposure tasks where a respirator is required? The standard seems to require the employer to “make medical surveillance available” but does not seem to require the employee to participate in the medical surveillance. Please clarify.

Response: Although the standard requires employers to make medical surveillance available to qualifying employees, the standard does not require qualifying employees to participate in medical surveillance. However, the employer must offer the examination fairly and in good faith, at no cost to employees, at a reasonable time and place, and must make another examination available if the employee requests it or, at a minimum, the next time an examination is due (i.e., within three years). See 29 CFR 1926.1153(h). In addition, the standard requires employers to train employees on the purpose and description of the medical surveillance program so employees understand that it is for their protection. See 29 CFR 1926.1153(i)(2)(i)(F). If an employer wishes to document an employee’s decision to decline a medical examination, the employer could ask the employee to sign a statement affirming that he or she was offered medical surveillance, but declined to participate.

Note that if respiratory protection is required for silica exposure tasks by the RCS construction standard, OSHA’s Respiratory Protection standard (29 CFR 1910.134) requires that the employer provide a medical evaluation to determine the employee’s ability to use a respirator before fit testing and use (see 29 CFR 1926.1153(e)(1), (e)(2), and 29 CFR 1910.134(e)). Whether or not the employee refuses medical surveillance under the RCS standard, the employee may perform silica exposure tasks that require respirator use only if he or she undergoes the medical evaluation required by the Respiratory Protection standard and is cleared to wear a respirator. Otherwise, the employer cannot assign the employee to a position that would require respirator use. For additional information on the medical evaluation requirements in 29 CFR 1910.134, see OSHA’s letter of interpretation to Mr. Gregory Norton, October 21, 2004.

Employers also have the option to adopt workplace requirements more stringent than OSHA’s, such as requiring a medical examination or laboratory test as a condition of employment, as long as the examination or test is not otherwise prohibited under applicable laws and/or labor-management contracts. OSHA has clarified this in a letter of interpretation, to Mr. Peter Lawton, February 2, 2018.

Question 8: When contractors are involved in sawing, grinding, demolition, and renovation activities involving presumed silica-containing materials such as tile, masonry and concrete on existing structures where the manufacturer/supplier of the silica- containing material is unknown, where is the employer to acquire a safety data sheet (SDS)? Would representative SDSs for similar products be acceptable to OSHA, for compliance with 29 CFR 1926.1153(i)?

Response: Where the manufacturer/supplier of the silica-containing material is unknown and employers are unable to obtain the SDS for the materials that are being worked upon by employees, the employer may use a representative SDS for training purposes to provide general information to affected employees. Even though OSHA does not require that SDSs specific to the silica-containing material be made available to employees in such situations, employers are required to provide information and training to their employees according to the provisions in OSHA’s Hazard Communication standard (29 CFR 1910.1200), and those at 29 CFR 1926.1153(i)(2)(i).

You might also find it useful to review the information in OSHA’s letter of interpretation to Mr. Robert Brooks, January 9, 1990.

Question 9: Drywall and drywall joint compound frequently contain only trace amounts of silica (frequently less than 1 percent). Is work on or with such materials covered by the standard?

Response: The RCS standard does not include an exemption based on the silica content of materials used. However, OSHA anticipates that employee exposures will typically remain below 25 µg/m3 as an 8-hour TWA when working with drywall or sanding joint compound that contains crystalline silica only as a trace contaminant, provided that the sanding is performed in isolation from other silica-generating tasks. Therefore, these tasks will generally be excluded from the scope of the standard per 29 CFR 1926.1153(a). However, employers should be aware that exposures could reach or exceed 25 µg/m3 as an 8-hour TWA in situations where employees are working with drywall or sanding joint compound for long periods of time in very dusty conditions. In such cases, employers must comply with the silica standard, including paragraph (d) (“alternative exposure control methods”), which requires employers to assess and limit the silica exposures of affected employees. See 29 CFR 1926.1153(d).

OSHA notes that dry sanding joint compound can potentially generate high levels of nuisance dust. Employers conducting such activities must implement control measures as necessary to limit employee exposure to nuisance dust. See 29 CFR 1926.55 Appendix A, Particulates not otherwise regulated.

You might also find it helpful to review the rest of the frequently asked questions (FAQs) on OSHA’s Silica Safety and Health Topics webpage, if you have additional questions related to the RCS standard for construction.

As you may be aware, North Carolina is one of 26 states plus Puerto Rico and the Virgin Islands that operates its own occupational safety and health program under a plan approved and monitored by federal OSHA. Employers in North Carolina must comply with state occupational safety and health requirements. As a condition of plan approval, State Plans are required to adopt and enforce occupational safety and health standards that are at least as effective as those promulgated by federal OSHA. A state’s interpretation of their standards must also be as least as effective as federal OSHA interpretations. If you would like further information regarding North Carolina’s occupational safety and health requirements, you may contact them at:

North Carolina Department of Labor
Occupational Safety and Health Division
1101 Mail Service Center
Raleigh, NC 27699-1101
Telephone: 1-800-NC-LABOR

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA’s website at www.osha.gov. If you have any further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.



Patrick J. Kapust, Acting Director
Directorate of Enforcement Programs


1 Occupational Exposure to Respirable Crystalline Silica, 29 CFR 1926.1153, Frequently Asked Questions for the Construction Industry, December 2018, https://www.osha.gov/dsg/topics/silicacrystalline/SilicaConstructionFAQs.pdf.