February 14, 2022

Dr. Gale R. Tipton, Jr.
Four Winds Ventures, LLC
1906 55th Street, Ct. East
Inver Grove Heights, MN 55077

Dear Dr. Tipton:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA), Directorate of Enforcement Programs. This is in response to your letter and phone conversation with a staff member requesting clarification on proper disposal of silica waste under OSHA's Respirable Crystalline Silica standards, 29 CFR § 1910.1053 and 29 CFR § 1926.1153. This letter constitutes OSHA's interpretation only of the requirements herein, and may not be applicable to any questions not delineated within your original correspondence. Your question is paraphrased below, followed by our response.

Question: What are the proper handling procedures and disposal for silica waste, including filters from dust collectors and personal protective equipment (PPE)?

Response: OSHA's Respirable Crystalline Silica standards do not specify procedures for disposal of silica waste including contaminated filters or PPE. However, the handling of such silica waste should be done in a manner to minimize employee exposure to respirable silica dust. Unless employee exposure will remain below the action level of 25 µg/m³ as an 8-hour time-weighted average (TWA) under any foreseeable conditions, or the employee is disposing of the contaminated filters or PPE as part of a task listed on Table 1 of the standard for construction (29 CFR § 1926.1153(c)(1)), the employer must assess employee exposure when removing or disposing of items contaminated with respirable crystalline silica following the Exposure assessment requirements found in 29 CFR § 1910.1053(d)(l) for general industry and maritime, or 29 CFR § 1926.1153(d)(2) for construction to determine if exposure levels exceed the Permissible Exposure Limit (PEL) of 50 μg/m³, calculated as an 8-hour TWA.

Employers covered by the general industry standard, and employers covered by the construction standard that are following alternative exposure control methods, must ensure that employees cleaning filters and disposing of dust are not exposed to silica above the PEL. See 29 CFR §1910.1053(c) and 29 CFR 1926.1153(d)(1), respectively. For employers who are following the specified exposure control methods listed in Table 1 of the construction standard, the tasks of filter cleaning and dust disposal are not separately listed on Table 1, but will often be performed as part of a Table 1 task. An employer following Table 1 must operate and maintain the relevant tool in accordance with the manufacturer's instructions to minimize dust emissions, which may include instructions for removing and cleaning filters and disposing of dust. Filters and PPE can be disposed of in sealed containers (such as heavy-duty plastic bags) to prevent or minimize the release of dust into the air.

For additional information on construction employees removing and cleaning filters used in dust collection systems and disposing of the dust, please refer to OSHA's Frequently Asked Questions for the Construction Industry, question #29, at https://www.osha.gov/silica-crystalline/construction-info.

Your letter mentioned that several filter manufacturers’ instruction manuals recommend cleaning filters with compressed air. Any manufacturer recommendations to clean filters using compressed air are not “manufacturer’s instructions to minimize dust emissions” per Table 1. This is because compressed air could cause silica dust to become airborne and contribute to employee exposure. Employers must be aware that where the use of compressed air to clean filters (or PPE) could contribute to employee exposure to respirable silica, it is prohibited unless it is either used together with a ventilation system that effectively captures the dust cloud, or where no other cleaning method is feasible. See 29 CFR § 1910.1053(h)(2), 1926.1153(f)(2). Use of a HEPA-filtered vacuum to clean filters and PPE is an example of a method that could be used to minimize dust emissions. Please be aware that Table 1, Specified Exposure Control Methods When Working With Materials Containing Crystalline Silica, requires many of the dust collectors to have a filter-cleaning mechanism (such as a reverse pulse feature). A cleaning mechanism will reduce the amount of times the filter needs to be removed for cleaning. For more information, please refer to OSHA's Controlling Silica Dust in Construction Fact Sheets for Table 1 Tasks, at https://www.osha.gov/silica-crystalline/construction.

For disposal of silica waste, OSHA has not specified disposal requirements for silica waste under the silica standards. We suggest that you check with your local municipality or state environmental protection office for waste management information or regulations on disposal of crystalline silica. You may also want to contact the U.S. Environmental Protection Agency (https://www.epa.gov/) on disposal requirements for silica waste.

As you may be aware, Minnesota 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 Minnesota 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 at least as effective as federal OSHA interpretations. If you would like further information regarding Minnesota's occupational safety and health requirements, you may contact them at:

Minnesota Occupational Safety and Health Administration
443 Lafayette Road North
St. Paul, MN 55155-4307
Toll Free (877) 470-6742, Tel: (651) 284-5050
Fax: (651) 284-5741

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 https://www.osha.gov.

If you have further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.

Sincerely,

Kimberly A. Stille, Director
Directorate of Enforcement Programs