Methylene chloride exposure requirements

The 8-hour time-weighted average (TWA) PEL for methylene chloride is 25 parts per million (ppm). Employers must ensure employee exposures do not exceed this limit as stated in 1910.1052(c)(1).

The STEL for methylene chloride is 125 ppm measured over a 15-minute sampling period. Employers must ensure no employee is exposed above this 15-minute limit as required by 1910.1052(c)(2).

The action level for methylene chloride is 12.5 ppm calculated as an 8-hour time-weighted average (TWA). This means employers use 12.5 ppm as the trigger for additional monitoring and program requirements under 1910.1052(b).

An employer must determine each employee's exposure by taking personal breathing zone air samples for each employee or by taking samples that are representative of each employee's exposure. The monitoring requirement is set out in 1910.1052(d)(1)(i).

An employer may use representative personal breathing zone samples when they sample at least one employee in each job classification per shift who is expected to have the highest MC exposure for that job: for 8-hour TWA monitoring follow 1910.1052(d)(1)(ii)(A), and for STEL monitoring follow 1910.1052(d)(1)(ii)(B).

Monitoring methods must be accurate to a 95 percent confidence level and be within ±25% for concentrations above the 8-hour TWA PEL or the STEL, and within ±35% for concentrations at or above the action level but at or below the 8-hour TWA PEL, as required by 1910.1052(d)(1)(iii).

Yes, an employer may avoid initial monitoring if objective data demonstrate that MC cannot be released at or above the action level or above the STEL under reasonably foreseeable conditions; the data must represent the highest likely exposures, per 1910.1052(d)(2)(i).

Prior monitoring performed within 12 months before April 10, 1997, can be used if it meets all other requirements of the MC standard and was conducted under conditions substantially equivalent to current conditions, according to 1910.1052(d)(2)(ii).

For employees exposed fewer than 30 days per year, employers may use direct-reading instruments that give immediate results (like detector tubes) to determine exposures and necessary controls instead of the full initial monitoring required by 1910.1052(d)(2)(iii).

When initial monitoring shows exposures at or above the action level but at or below the TWA, the employer must monitor 8-hour TWA exposures every six months, as shown in the exposure monitoring requirements in 1910.1052(d)(3).

Employers must monitor STEL exposures every three months when initial monitoring indicates exposures above the STEL, and certain industries (e.g., polyurethane foam manufacturing, furniture refinishing, general aviation aircraft stripping, and specified construction uses) must monitor STEL every three months until they meet the TWA compliance schedule or achieve the TWA PEL, per 1910.1052(d)(3).

An employer may decrease or discontinue periodic monitoring when at least two consecutive measurements taken at least seven days apart show exposures are at or below the applicable limits: decrease 8-hour TWA monitoring to every six months or discontinue it if two consecutive measurements are below the action level; discontinue STEL monitoring if two consecutive measurements are at or below the STEL, per the note to 1910.1052(d)(3).

The employer must perform additional monitoring if changes in workplace conditions (like production, processes, control equipment, or work practices) indicate exposures may have increased and must clean up spills or make repairs before monitoring after a leak or breakdown, as required by 1910.1052(d)(4)(i)-(ii).

The employer must notify each affected employee in writing of monitoring results within 15 working days after receiving them, either individually or by posting results in an accessible location; if results exceed the 8-hour TWA PEL or STEL, the notice must describe corrective actions and the schedule for completing them, per 1910.1052(d)(5)(i)-(ii).

Employees or their designated representatives have the right to observe any monitoring of MC exposure, and if observation requires entry into an area where protective clothing or equipment is needed, the employer must provide that clothing and equipment at no cost and the observer must use it as required by 1910.1052(d)(6)(i)-(ii).

The MC standard applies to all occupational exposures to methylene chloride in general industry, construction, and shipyard employment, per 1910.1052(a).

'Employee exposure' means exposure to airborne MC that would occur if the employee were not using respiratory protection; employers base monitoring and compliance on this unprotected exposure definition as given in 1910.1052(b).

For exposures above the 8-hour TWA PEL or the STEL, monitoring must be accurate within ±25% at the 95% confidence level; for exposures at or above the action level but at or below the TWA, monitoring must be accurate within ±35% at the 95% confidence level, per 1910.1052(d)(1)(iii)(A)-(B).

Yes, a personal breathing zone sample taken during one shift may represent exposures on other shifts if the employer documents that tasks and workplace conditions are similar across shifts, as allowed in 1910.1052(d)(1)(iii).

Before monitoring following a spill, leak, or breakdown, the employer must clean up the methylene chloride and perform appropriate repairs, as required by 1910.1052(d)(4)(ii).

Employers in industries such as polyurethane foam manufacturing and fabrication; furniture refinishing; general aviation aircraft stripping; product formulation; use of MC-based adhesives for boat building and repair, recreational vehicle manufacture, van conversion, or upholstery; and certain construction uses must monitor STEL every three months until they meet their TWA schedule or achieve the TWA PEL, according to the special provision in 1910.1052(d)(3).

The written notification must describe the corrective actions being taken to reduce exposures to or below the 8-hour TWA PEL or STEL and include the schedule for completing those actions, as required by 1910.1052(d)(5)(ii).

The employer must provide required protective clothing and equipment at no cost to the observer, and the observer must use that clothing and comply with applicable safety procedures while observing monitoring under 1910.1052(d)(6)(ii).

A regulated area must be established where an employee's exposure to airborne MC exceeds or can reasonably be expected to exceed either the 8-hour TWA PEL (25 ppm) or the STEL (125 ppm), as defined in the standard's definitions and monitoring requirements in 1910.1052(b) and implied by the monitoring and control provisions of 1910.1052(d).

An employer must establish a regulated area wherever employee airborne exposures to methylene chloride exceed or can reasonably be expected to exceed the 8-hour TWA PEL or the STEL. See 1910.1052(e)(1).

• Make the determination based on exposure monitoring, predictable work tasks, or process schedules that could push exposures above the limits.
• Once a regulated area is established, follow the other requirements in 1910.1052(e).

Only authorized persons may enter a regulated area for methylene chloride. See 1910.1052(e)(2).

• "Authorized" means employees trained and permitted by the employer to work in that area under the protections required by the standard.
• Employers should limit access to reduce the number of people potentially exposed.

An employer must supply and require the use of respirators in a regulated area whenever MC exposures are likely to exceed the 8-hour TWA PEL or the STEL. See 1910.1052(e)(3).

• If exposures only exceed limits on predictable days (for example, certain process or work schedules), respirators are required only on those days—the standard allows this conditional use in the note to 1910.1052(e)(3).
• Respirators must be selected in accordance with 1910.1052(h)(3) (see the respirator selection rules in the standard).

No — the employer must ensure that, within a regulated area, employees do not engage in non-work activities that may increase dermal or oral exposure to methylene chloride. See 1910.1052(e)(4).

• Examples of prohibited activities include eating, drinking, smoking, applying cosmetics, or chewing gum in the regulated area.
• Employers should post clear signs and provide separate clean areas for those activities outside the regulated area.

Employers must ensure employees do not engage in activities (like taking medication or chewing gum or tobacco) that interfere with respirator seal or performance while wearing respirators. See 1910.1052(e)(5).

• Train employees on behaviors that break the facepiece seal (e.g., eating, drinking, smoking, using chewing tobacco).
• Enforce these restrictions whenever respirators are required by the standard.

Regulated areas must be clearly demarcated to alert employees to their boundaries and limit authorized access, and at multi-employer worksites the employer must communicate these areas and access restrictions to all other employers on site. See 1910.1052(e)(6) and 1910.1052(e)(7).

• Use physical barriers, signs, colored tape, or other methods that reliably show boundaries.
• At multi-employer sites, give other employers the locations and rules for these areas so they can keep their employees out or protected.

Employers must first use feasible engineering controls and work practices to reduce MC exposures to or below the PELs, and employee rotation cannot be used to comply with the PELs. See 1910.1052(f)(1) and 1910.1052(f)(2).

• Examples of engineering controls: local exhaust ventilation, enclosure of processes, or substitution if feasible.
• If controls cannot fully reduce exposures, employers must lower exposures to the lowest achievable level and supplement with respirators as required by the standard.

Employers must implement procedures to detect MC leaks, contain spills, safely dispose of MC-contaminated waste, repair incidental leaks, and promptly clean incidental spills using trained employees with appropriate PPE. See 1910.1052(f)(3) and 1910.1052(f)(3)(ii).

• Train employees in cleanup methods and provide PPE resistant to MC.
• Employers covered by this standard may also need to follow the hazardous waste and emergency response rules in 1910.120(q).

Respirators must be used when exposures exceed the 8-hour TWA PEL or the STEL, when implementing controls, for certain maintenance tasks where controls are infeasible, and for emergencies; employers must implement a respiratory protection program meeting [1910.13(b)–(m)]. See 1910.1052(g)(1) and 1910.1052(g)(2)(i).

• The program must follow the elements listed in 1910.13 (medical evaluations, fit testing, training, maintenance, recordkeeping, etc.).
• For provided emergency gas masks with organic-vapor canisters, replace canisters after any emergency use per 1910.1052(g)(2)(ii).

Employers must select and provide the appropriate atmosphere-supplying respirator specified in [29 CFR 1910.134(d)(3)(i)(A)], and must not select or use any type of half-mask because MC can irritate or damage the eyes. See 1910.1052(g)(3)(i) and 1910.134(d)(3)(i)(A).

• Atmosphere-supplying respirators (e.g., supplied-air respirators) are required for routine use when exposures warrant them.
• Do not rely on half-mask air-purifying respirators for MC exposures because they do not protect the eyes from irritating vapors.

For emergency escape from methylene chloride, employers must provide either a self-contained breathing apparatus (SCBA) operated in continuous-flow or pressure-demand mode, or a gas mask with an organic vapor canister. See 1910.1052(g)(3)(ii).

• If you provide gas masks with organic-vapor canisters for escape, replace the canisters after any emergency use before returning the masks to service as required in 1910.1052(g)(2)(ii).
• Ensure employees are trained in the use and limitations of the chosen escape devices.

Before an employee uses a supplied-air respirator in the negative-pressure mode or a gas mask with an organic-vapor canister for emergency escape, the employer must have a physician or other licensed health-care professional (PLHCP) evaluate the employee's ability to use that respiratory protection and provide a written opinion. See 1910.1052(g)(4)(i) and 1910.1052(g)(4)(ii).

• The PLHCP must document findings in a written opinion to the employee and employer.
• Maintain confidentiality of medical information as required by other applicable rules.

Where needed to prevent MC-induced skin or eye irritation, the employer must provide clean protective clothing and equipment that is resistant to methylene chloride at no cost to the employee, and must ensure affected employees use it; eye and face protection must meet [29 CFR 1910.133] standards. See 1910.1052(h)(1) and 1910.133.

• Choose materials and gloves proven compatible with MC (consult manufacturer permeation data).
• Provide and require splash goggles or face shields when eye exposure is possible per 1910.133.

The employer must clean, launder, repair and replace all required protective clothing and equipment as needed to maintain effectiveness and is responsible for the safe disposal of such clothing and equipment. See 1910.1052(h)(2) and 1910.1052(h)(3).

• Follow the examples in Appendix A for acceptable disposal procedures.
• Treat MC-contaminated materials per employer procedures and any applicable hazardous waste regulations.

If it is reasonably foreseeable that employees' skin may contact solutions containing 0.1% or greater methylene chloride, employers must provide conveniently located washing facilities; if eye contact is reasonably foreseeable with solutions ≥0.1% MC, employers must provide appropriate eyewash facilities in the immediate work area. See 1910.1052(i)(1) and 1910.1052(i)(2).

• Ensure employees know when and how to use these facilities and encourage immediate decontamination after splashes or spills.
• Eyewash stations should be within the immediate work area and meet applicable flushing requirements.

Medical surveillance must be made available to employees who are or may be exposed to MC at or above the action level for 30 or more days per year, or above the 8-hour TWA PEL or STEL on 10 or more days per year, and the employer must provide all required medical surveillance at no cost to employees, without loss of pay and at a reasonable time and place. See 1910.1052(j)(1)(i) and 1910.1052(j)(2).

• Also provide surveillance if a PLHCP identifies an employee as at special risk and requests inclusion 1910.1052(j)(1)(ii).
• Make arrangements so employees do not lose pay for surveillance visits.

The employer must provide initial medical surveillance per the schedule in 1910.1052(n)(2)(iii) or before initial assignment, whichever is later; periodic surveillance requires annual updates to medical/work history and physical exams at specified intervals: within 12 months for employees ≥45 years old and within 36 months for employees under 45. See 1910.1052(j)(4)(i) and 1910.1052(j)(4)(ii).

• If an employee leaves or is reassigned to consistently lower-exposure areas and six months or more have passed since last surveillance, make surveillance available upon termination/reassignment per 1910.1052(j)(4)(iii).
• Provide additional surveillance at frequencies recommended in the written medical opinion 1910.1052(j)(4)(iv).

Medical surveillance must include a comprehensive medical and work history emphasizing neurological, skin, hematologic, liver, and cardiac signs and symptoms, a physical exam with emphasis on lungs, cardiovascular system, liver, nervous system, and skin, and laboratory surveillance as determined by the PLHCP. See 1910.1052(j)(5)(i), 1910.1052(j)(5)(ii), and 1910.1052(j)(5)(iii).

• Laboratory tests may include carboxyhemoglobin (before/after shift), resting ECG, hematocrit, liver function tests, and cholesterol when deemed necessary by the PLHCP 1910.1052(j)(5)(iii).
• The PLHCP decides the exact tests and exam extent based on the employee's history and observed health.

All medical surveillance procedures must be performed by a physician or other licensed health care professional (PLHCP) as defined in the standard, and the employer must provide required medical surveillance at no cost to the employee. See 1910.1052(j)(3) and 1910.1052(j)(2).

• Employers should ensure the PLHCP documents and provides written medical opinions as required elsewhere in the standard.
• Keep required confidentiality of medical records while making necessary information available to PLHCP and employees.

For periodic medical surveillance: employees 45 years of age or older must have examinations within 12 months of initial surveillance or subsequent surveillance, while employees younger than 45 must have examinations within 36 months. See 1910.1052(j)(4)(ii)(A) and 1910.1052(j)(4)(ii)(B).

• Update the medical and work history annually for all affected employees as part of surveillance 1910.1052(j)(4)(ii).

The employer must ensure emergency medical surveillance includes immediate treatment/decontamination, a comprehensive physical exam focused on key organ systems, an updated medical/work history, and laboratory surveillance as indicated. These minimum elements are set out in 1910.1052(j)(6).

• Emergency treatment and decontamination of the exposed employee are required.
• A comprehensive physical exam must emphasize the nervous, cardiovascular, pulmonary, hepatic, and dermal systems and include blood pressure and pulse checks.
• The employer must update the employee’s medical and work history as appropriate for the condition.
• Laboratory surveillance must be provided as indicated by the employee’s health status (see the Note to 1910.1052(j)(6)(iv)).

If the PLHCP (physician or licensed health care professional) determines further testing or referrals are necessary, the employer must expand the scope of surveillance in accordance with 1910.1052(j)(7).

The employer must provide the PLHCP a copy of the MC medical surveillance rule, exposure information, job duties, PPE details, and prior medical surveillance data. These items are listed in 1910.1052(j)(8).

Specifically the employer must give the PLHCP:

• A copy of the standard and applicable appendices (1910.1052(j)(8)(i)).
• A description of the employee’s past, current, and anticipated future duties as they relate to MC exposure (1910.1052(j)(8)(ii)).
• The employee’s former or current exposure levels, or anticipated exposure levels and frequency for those not yet exposed (1910.1052(j)(8)(iii)).
• A description of any respirators or protective clothing used or to be used (1910.1052(j)(8)(iv)).
• Information from prior employment-related medical surveillance not otherwise available to the PLHCP (1910.1052(j)(8)(v)).

Providing complete and accurate exposure and PPE information helps the PLHCP make appropriate medical judgments about surveillance, removal, and treatment.

The written medical opinion must state whether MC exposure may contribute to or aggravate specified diseases, any recommended exposure limitations, that the employee was informed MC is a potential carcinogen and of relevant risks, and the results requiring further explanation or treatment; the physician must not disclose unrelated specific medical records or diagnoses. These requirements appear in 1910.1052(j)(9)(i) and the privacy limitation in 1910.1052(j)(9)(ii).

Required items the written opinion must include:

• The PLHCP’s opinion on whether MC exposure may contribute to or worsen cardiac, hepatic, neurological (including stroke), or skin disease or otherwise place the worker at increased risk (1910.1052(j)(9)(i)(A)).
• Any recommended limitations on MC exposure or use of respirators/protective clothing (1910.1052(j)(9)(i)(B)).
• A statement that the employee was informed that MC is a potential occupational carcinogen and informed about heart disease risk factors and potential exacerbation via metabolism to carbon monoxide (1910.1052(j)(9)(i)(C)).
• A statement that the employee was informed of the exam results and any conditions needing further explanation or treatment (1910.1052(j)(9)(i)(D)).

Privacy limitation:

• The PLHCP must be instructed not to disclose to the employer any specific records, findings, or diagnoses that have no bearing on occupational MC exposure (1910.1052(j)(9)(ii)).

These rules balance the employer’s need for work-related medical guidance with the employee’s right to medical privacy.

The PLHCP must presume that medical removal is unlikely to be required if the employee is not exposed above the 8‑hour TWA PEL, and a PLHCP recommendation for removal at exposures below the PEL must cite specific medical evidence to rebut that presumption. This presumption and the rebuttal requirement are stated in 1910.1052(j)(10).

• If the PLHCP recommends removal despite exposures being below the 8‑hour TWA PEL, the PLHCP must cite specific medical evidence sufficient to rebut the presumption that removal is unnecessary at those exposure levels.
• If the PLHCP cites such medical evidence, the employer must remove the employee as recommended; if not, the employer is not required to remove the employee.

This rule ensures removal decisions below the PEL are based on individualized, documented medical findings rather than on exposure level alone.

When a PLHCP recommends removal because MC may aggravate certain diseases, the employer must provide MRP benefits and either transfer the worker to comparable low‑exposure work or remove them from MC exposure; MRP means maintaining earnings, seniority, and benefits for up to six months as if the employee had not been removed. These duties are described in 1910.1052(j)(11)(i) and 1910.1052(j)(12).

Key employer obligations:

• Provide medical removal protection benefits (MRP) and either transfer the employee to comparable work where exposure is below the action level or remove the employee from MC exposure (1910.1052(j)(11)(i)(A)).
• If comparable work is not available and the employer can show removal isn’t feasible considering business size and the standard, the employer may temporarily retain the employee in the existing job only if the employer provides additional medical surveillance at least every 60 days and informs the employee of the risk (1910.1052(j)(11)(i)(B)).
• MRP benefits require maintaining earnings, seniority, and other employment rights and benefits for up to six months as though the employee had not been removed (1910.1052(j)(12)(i)).
• The employer may condition MRP on the employee’s participation in follow-up medical surveillance (1910.1052(j)(12)(ii)).
• If the employee files a workers’ compensation claim, MRP must continue until the claim is resolved or the six‑month period ends, whichever comes first (1910.1052(j)(12)(iii)).

These provisions protect employees while recognizing employer operational constraints; consult the cited sections for timing and documentation details.

An employee has the right to a second medical opinion paid by the employer, and if the two PLHCPs disagree they must try to resolve the difference or select a jointly designated specialist whose definitive written opinion the employer must follow. These rights and procedures are stated in 1910.1052(j)(14).

Procedure summary:

• The employer must notify the employee of the right to seek a second opinion each time the employer provides a copy of the employer‑selected PLHCP’s written opinion (1910.1052(j)(14)(i)).
• If the employee disagrees, notifies the employer, and schedules a second PLHCP within 15 days, the employer must pay for the second PLHCP to review the initial findings and conduct any examinations/tests the second PLHCP deems necessary (1910.1052(j)(14)(ii)).
• If the two PLHCPs disagree, they must try to resolve the disagreement; if they cannot within 15 days they must jointly designate a specialist in the field, and the employer pays for the specialist’s review and any necessary testing (1910.1052(j)(14)(iii)–(iv)).
• The specialist’s written opinion is the definitive medical determination and the employer must act consistently with it unless the employer and employee agree otherwise (1910.1052(j)(14)(v)).

These steps ensure an independent review and a clear path to a binding medical determination when disputes arise.