Methylenedianiline scope and application

Yes. 1926.60(a)(1) says the standard applies to all construction work as defined in 29 CFR 1910.12(b) when employees can be exposed to MDA.

• Examples include work on structures that contain MDA, installing or finishing surfaces with MDA-containing products, cleanup of MDA spills at job sites, and on-site storage, transport, or disposal of MDA or MDA-containing products, per 1926.60(a)(1)(i)–(iv).

You may skip initial monitoring only if you can demonstrate the product cannot release MDA above the action level under the worst-case conditions or you have valid historical monitoring data. 1926.60(a)(2) allows skipping monitoring when initial testing shows the product won't release MDA above the action level and no dermal exposure can occur; 1926.60(a)(3) allows relying on objective data that reasonably demonstrate the same.

• Also see the monitoring exception in 1926.60(f)(2)(i)–(ii), which mirrors these criteria for avoiding initial exposure monitoring.

Generally no. 1926.60(a)(4) excludes storage, transportation, distribution, or sale of MDA in intact sealed containers from most of the standard’s requirements, except that you still must comply with the Hazard Communication requirements in 29 CFR 1910.1200 and the emergency provisions in paragraph (e) of this section.

Yes. 1926.60(a)(5) states the standard does not apply to materials that contain less than 0.1% MDA by weight or volume, except as provided in paragraph (a)(7) which requires recordkeeping of the basis for the exemption.

• Note that the definitions in 1926.60(b) clarify when dermal exposure may exist and the threshold concentrations relevant to exemptions.

You must keep records that document the initial monitoring results or objective data and the basis for relying on them. 1926.60(a)(7) requires employers to maintain those records as provided in the recordkeeping provisions of paragraph (o) of the standard.

• Keep documentation showing the data are scientifically sound and applicable to your process (see the historical data criteria in 1926.60(b)).

The action level for airborne MDA is 5 parts per billion (ppb) as an 8-hour time-weighted average. 1926.60(b) defines the action level used throughout the standard.

• Exposures at or above the action level trigger monitoring and additional protections described in the standard.

Employers must ensure employee exposure does not exceed 10 ppb as an 8‑hour TWA and 100 ppb as a 15‑minute STEL. 1926.60(c) sets these PELs and the STEL for airborne MDA.

• If exposures exceed these limits, employers must take steps such as engineering controls, work practices, and respiratory protection as required elsewhere in the standard.

The employer who performs work requiring regulated areas must inform other employers on the site about the nature of the work and the existence and requirements of regulated areas. 1926.60(d) requires this communication so all employers and employees on the site know where MDA hazards and regulated areas exist.

• This helps coordinating employers meet obligations for access controls, PPE, and worker protection.

You must prepare a written emergency plan that identifies emergency escape routes before work starts, implements appropriate portions during an emergency, equips employees correcting emergencies with required PPE, and includes alerting and evacuation procedures consistent with 29 CFR 1910.38 and 29 CFR 1910.39. 1926.60(e)(1)(i)–(iii) details these requirements.

• The plan must also specify that employees correcting emergency conditions wear the protective equipment required by paragraphs (i) and (j) of the MDA standard until the emergency is abated.

Affected employees not engaged in correcting the emergency must be evacuated immediately and you must have means to promptly alert employees who may be directly exposed or indirectly affected. 1926.60(e)(2) requires procedures to alert both directly exposed employees and others who may be exposed because of the emergency.

• The written plan in 1926.60(e)(1) must describe these alerting and evacuation methods.

Breathing-zone air samples representative of each employee’s exposure must be used: full-shift samples for the 8‑hour TWA and 15‑minute breathing‑zone samples for the STEL. 1926.60(f)(1)(i) requires these sampling approaches to determine compliance with the 8‑hour PEL and STEL.

• Use representative sampling that reflects each employee’s actual breathing-zone exposures.

Initial monitoring is required for all workplaces covered by the standard unless you can demonstrate by objective data that the product cannot cause exposures above the action level under worst‑case conditions or you have historical monitoring showing exposures will be below the action level. 1926.60(f)(2) with exceptions in 1926.60(f)(2)(i)–(ii).

• If you rely on objective data or historical monitoring, document the basis carefully as required elsewhere in the standard.

If exposures are at or above the action level but at or below the PELs, repeat monitoring at least every six months; if above the PELs, repeat monitoring at least every three months. 1926.60(f)(3)(i)–(ii) details these frequencies.

• Employers conducting operations inside a regulated area may forego periodic monitoring if all employees wear supplied‑air respirators while working in that area, per 1926.60(f)(3)(iii).

You may change monitoring from every three months to every six months for an employee when two consecutive measurements taken at least 7 days apart show exposure decreased to below the PEL but above the action level. 1926.60(f)(3)(iv) allows this. Monitoring may be discontinued if initial monitoring shows exposures below the action level, subject to the exception in 1926.60(f)(5).

• Also, 1926.60(f)(4)(ii) allows discontinuing periodic monitoring after two consecutive measurements (≥7 days apart) below the action level.

You must start exposure monitoring whenever there is a change in process, chemicals, control equipment, personnel, or work practices that may create new or additional MDA exposures, or whenever you have any reason to suspect such a change. 1926.60(f)(5) requires instituting monitoring under those conditions.

• Think of this as a “trigger” for re‑evaluating exposure whenever workplace conditions that affect exposure change.

Monitoring must be accurate to a 95 percent confidence level within ±25 percent for airborne concentrations of MDA. 1926.60(f)(6) specifies this accuracy requirement.

• Use validated sampling and analytical methods that meet this accuracy to support compliance decisions.

You must notify each affected employee of monitoring results as soon as possible but no later than 5 working days after you receive them, either individually in writing or by posting results in an accessible location. 1926.60(f)(7)(i) requires this timeframe and methods.

• Keep documentation of the notifications in case you need to demonstrate compliance.

Dermal exposure to MDA occurs when workers handle or apply mixtures or materials containing MDA in non‑airborne forms—specifically (i) liquid, powdered, granular, or flaked mixtures with more than 0.1% MDA, or (ii) materials other than finished articles containing more than 0.1% MDA. 1926.60(b) defines these conditions.

• When dermal exposure can occur, the standard’s requirements apply even if airborne levels are low.

Finished articles are generally excluded: 1926.60(a)(6) except where paragraph (a)(7) overrides exemptions. The standard defines a finished article as an item formed to a specific shape or design, with end‑use functions tied to its shape or design, and, where applicable, fully cured by the conditions necessary to complete the chemical reaction. See the finished article definition in 1926.60(b).

• If the item can still release MDA or allow dermal contact as defined elsewhere, the exclusion may not apply; document applicability carefully.

Employers must include spill/emergency cleanup in the scope of the standard and have a written emergency plan that equips employees correcting emergency conditions with appropriate PPE and clothing until the emergency is abated. 1926.60(a)(1)(iii) covers MDA spill cleanup and 1926.60(e)(1)(ii) requires that employees engaged in correcting emergency conditions be provided the personal protective equipment specified by the standard.

• The plan must also include escape routes and alert/evacuation procedures per 1926.60(e)(1)(i)–(iii).

The employer must determine the source of the exposure, implement protective measures to correct the hazard, and keep records of those corrective actions. Employers must follow the steps set out in 1926.60(f)(8) and its subparagraphs: determine the source of exposure (1926.60(f)(8)(i)), implement protective measures (1926.60(f)(8)(ii)), and maintain records of corrective actions in accordance with paragraph (o) (1926.60(f)(8)(iii)).

• Refer any other potential dermal exposures reported by the employee to appropriate medical personnel for observation as required in 1926.60(f)(8).
• Keep clear records of what corrective actions were taken and where those records are stored per paragraph (o).

An employer must establish a regulated area when airborne concentrations of MDA exceed or can reasonably be expected to exceed the permissible exposure limits (PELs). This requirement is stated in 1926.60(g)(1)(i).

• Regulated areas are specifically for airborne overexposure risk; separate requirements apply for dermal exposure under 1926.60(g)(1)(ii).

If employees are subject to dermal exposure to MDA, the employer must establish those work areas as regulated areas. See 1926.60(g)(1)(ii).

• This means areas where skin contact with MDA could occur must be treated with the same controlled access and protections as areas with airborne overexposures.

Regulated areas must be demarcated to minimize the number of persons potentially exposed, and access must be limited to authorized persons only. These requirements are in 1926.60(g)(2) and 1926.60(g)(3).

• Demarcation should make clear boundaries (signs, barriers, markings) so casual traffic is prevented.
• Only employees who are authorized and trained to work in the regulated area should be allowed inside.

The employer must supply and require use of the appropriate protective clothing and equipment for anyone entering a regulated area, in accordance with 1926.60(g)(4) and the types listed in 1926.60(j)(1).

• Required items include aprons, coveralls or full-body clothing; gloves, head and foot coverings; face shields or chemical goggles; and other equipment that complies with 29 CFR 1910.133.
• All required PPE must be provided at no cost to employees and employees must be required to use it while in the regulated area.

Employees must not eat, drink, smoke, chew tobacco or gum, or apply cosmetics in regulated areas. This prohibition is stated in 1926.60(g)(5).

• Employers should enforce these rules and provide clean break/lunch areas that are free from MDA exposure as required elsewhere in the standard.

Employers must use one or a combination of local exhaust ventilation with HEPA filter dust collection, general ventilation systems, safe work practices, or other feasible engineering controls such as isolation or enclosure to meet the PELs. See 1926.60(h)(1)(i) and its subparagraphs (A–D).

• Use HEPA-filtered local exhaust where dusts are generated.
• Use engineering controls before relying on respirators whenever feasible.

When feasible engineering controls and work practices cannot reduce exposures to or below the PELs, employers must use them to lower exposure as much as possible and supplement them with respirators that meet the requirements of paragraph (i). See 1926.60(h)(1)(ii).

• Respirators are a supplement when controls alone are insufficient; they are not a first choice if engineering solutions can achieve compliance.

For workers using spray application methods, respirators must be used in addition to feasible engineering controls and work practices to reduce exposure to or below the PELs. This is required by 1926.60(h)(2).

• In spray operations, expect to provide both engineering controls (e.g., ventilation, containment) and appropriate respirators.

Compressed air cannot be used to remove MDA unless it is used with an enclosed ventilation system designed to capture the dust cloud created by the compressed air. See 1926.60(h)(3).

• If compressed air is necessary, ensure an engineering control is in place that captures the dust and prevents re-entry of MDA into the workplace.

No—employers are prohibited from using employee rotation as a means of complying with the exposure limits in paragraph (c). This prohibition is in 1926.60(h)(4).

• Employers must rely on controls and respirators as allowed, not on rotating workers to reduce measured exposures.

Employers must establish and implement a written program to reduce employee exposure to or below the PELs by engineering and work practice controls and by using respiratory protection when permitted; upon request the program must be furnished to the Assistant Secretary, the Director, affected employees, and designated employee representatives. See 1926.60(h)(5)(i) and (h)(5)(ii).

• The program must be reviewed and updated at least once every 12 months to reflect the current status.

Employers must provide and require respirator use during periods necessary to install or implement feasible controls, for operations (e.g., maintenance, repair, spray application) where controls are not feasible, when controls are not yet sufficient to reduce exposures to PELs, and during emergencies. See 1926.60(i)(1)(i)–(iv).

• Respirators are required for short-term tasks while controls are being implemented, for specific operations where controls can’t be used, and for emergencies.

The employer must implement a respiratory protection program in accordance with 1910.134(b)–(d) (except (d)(1)(iii)) and (f)–(m), covering each employee required by this section to use a respirator, as specified in 1926.60(i)(2).

• That means following the selection, medical evaluation, fit testing, training, maintenance, and recordkeeping rules in 29 CFR 1910.134.

Employers must select respirators specified in 29 CFR 1910.134(d)(3)(i)(A), provide HEPA filters for powered and non-powered air-purifying respirators, provide specific escape respirators (SCBA full facepiece or full facepiece APR), and supply a combination HEPA filter and organic vapor canister when MDA is in liquid form or used with heat. See 1926.60(i)(3)(i)(A)–(D).

• Use HEPA filters to protect against MDA particulates.
• For liquid MDA or heated processes that vaporize MDA, add organic vapor protection to HEPA filtration.

If an employee cannot use a negative-pressure respirator, the employer must give the employee the option of a positive-pressure respirator or a supplied-air respirator operated in continuous-flow or pressure-demand mode. See 1926.60(i)(3)(ii).

• This ensures employees who fail fit tests, have facial hair, or have other limitations still have acceptable respiratory protection options.

When employees are subject to dermal exposure to MDA, where liquids containing MDA can be splashed into the eyes, or when airborne concentrations exceed the PEL, employers must provide, at no cost, appropriate protective clothing and equipment such as aprons, coveralls, gloves, head and foot coverings, face shields, and chemical goggles. See 1926.60(j)(1) and the eye/face protection requirement in 29 CFR 1910.133.

• Employers must ensure the PPE prevents contact with MDA and complies with applicable consensus standards.

Employers must ensure employees remove MDA-contaminated protective clothing that is not routinely removed during the day at the end of their shift in change areas provided under paragraph (k); employees must remove other contaminated clothing before leaving a regulated area; and contaminated items may not be taken out of decontamination areas except by authorized employees for laundering, maintenance, or disposal. See 1926.60(j)(2)(i)–(iii).

• Change areas must include separate storage for protective and street clothing as required by 1926.60(k)(1)(ii) and 29 CFR 1910.141(e).

MDA-contaminated clothing or equipment must be placed, stored, and transported in sealed, impermeable bags or other closed impermeable containers, and any containers of contaminated clothing taken out for laundering, maintenance, or disposal must bear labels warning of MDA hazards. See 1926.60(j)(2)(iv)–(v).

• Use clear, durable labels that communicate the hazard to laundry and maintenance personnel.

The employer must provide clean protective clothing and equipment, ensure required items are cleaned, laundered, repaired, or replaced as needed to maintain effectiveness, prohibit removal of MDA by blowing or shaking, ensure laundering prevents release of MDA into the workplace, and inform any third-party launderer of the hazards and requirements. See 1926.60(j)(3)(i)–(v).

• Employers must communicate hazards and handling requirements to outside laundry services and eliminate work practices that could reintroduce MDA into the workplace.

Employers must ensure employees' work clothing is examined periodically for rips or tears and that any damaged protective equipment is repaired or replaced immediately. See 1926.60(j)(4)(i)–(ii).

• A simple inspection checklist and prompt replacement protocol will help meet this requirement and keep PPE effective.

Employers must provide decontamination areas for employees required to work in regulated areas or to wear protective clothing under paragraph (j)(1), except for small-scale, short-duration operations where employees may clean or dispose of PPE before leaving the work area; change areas must have separate storage for protective clothing and street clothing in accordance with [29 CFR 1910.141(e)]. See 1926.60(k)(1)(i)–(ii).

• Provide clearly separated and labeled storage and procedures so street clothing cannot be contaminated.
• For small, short jobs, the exception allows on-site cleaning/disposal before leaving the work area.

Where feasible, employers must provide shower facilities that comply with 29 CFR 1910.141(d)(3) wherever the possibility of airborne MDA exposure above the PEL exists, and where dermal exposure occurs employers must ensure spilled or deposited material on skin is removed promptly by methods that do not facilitate dermal absorption. See 1926.60(k)(2)(i)–(ii).

• Use gentle washing methods and avoid solvents or practices that increase skin uptake of MDA.

When food or beverages are consumed at the worksite and employees are exposed to MDA, the employer must provide clean lunch areas where MDA levels are below the action level and no dermal exposure can occur; ensure employees wash hands and faces with soap and water before eating, drinking, smoking, or applying cosmetics; and prevent employees from entering lunch facilities while wearing contaminated protective clothing. See 1926.60(k)(3)(i)–(iii).

• Keeping eating areas separate and enforcing hygiene practices prevents ingestion or further contact with MDA.

Employers must include MDA in the hazard communication program required by the Hazard Communication Standard and must post legible signs demarcating regulated areas with the required legend warning of cancer and liver damage and stating that respiratory protection and protective clothing may be required. See 1926.60(l)(1) and the sign text in 1926.60(l)(2)(i)(A), and include MDA information under 29 CFR 1910.1200.

• Ensure labels, SDSs, employee training, and posted signs cover hazards such as cancer, liver effects, and skin sensitization as required by the standard.

The employer must ensure that labels or other appropriate forms of warning are provided for containers of MDA within the workplace. This is required by 1926.60(l)(2)(ii)(A) and is part of the Hazard Communication Standard obligations in 29 CFR 1910.1200.

• Labels should be legible, durable, and include hazard information consistent with SDSs and training.

The written notification must state the corrective action being taken or other protective measures implemented to reduce employee exposure to or below the PELs. This requirement is specified in 1926.60(f)(7)(ii).

• Make the notification clear about what steps are being taken, timelines, and who is responsible so employees and regulators can verify follow-up.

When an employee reports a potential dermal exposure, the employer must refer that potential exposure to appropriate medical personnel for observation, inspect the exposed areas visually, determine the exposure source if exposure occurred, implement protective measures to correct the hazard, and keep records of corrective actions. See 1926.60(f)(8) and its subparts (i–iii).

• Prompt referral to medical personnel helps assess need for treatment and documents potential occupational exposures for recordkeeping.

Yes—prior to June 1, 2016, employers were permitted to use an alternate sign legend in lieu of the legend specified in [1926.60(l)(2)(i)(A)]. The alternate legend is described in 1926.60(l)(2)(i)(B).

• After June 1, 2016, employers should use the updated legend in 1926.60(l)(2)(i)(A) unless otherwise directed by OSHA guidance.

Employers must post the required MDA workplace labels and give employees MDA information and training at initial assignment and at least annually, including MDA‑specific topics beyond generic Hazard Communication training.

• Labels: Labels must meet the Hazard Communication labeling requirements in 1910.1200(f) and, for current labels, must include at least the following wording for pure MDA and for mixtures containing MDA:
  • DANGER
  • CONTAINS MDA
  • MAY CAUSE CANCER
  • CAUSES DAMAGE TO THE LIVER
  (See 1926.60(l)(2)(ii)(B)).

  • Note: Employers may use the pre‑June 1, 2015 alternative workplace label wordings where applicable: for pure MDA use the wording at 1926.60(l)(2)(ii)(B)(1) and for mixtures use the wording at 1926.60(l)(2)(ii)(B)(2).

• Training timing and baseline requirement: Employers must provide information and training on MDA in accordance with 1910.1200(h) at the time of initial assignment and at least annually thereafter, as required by 1926.60(l)(3)(i).

• MDA‑specific training content: In addition to the general Hazard Communication topics, employers must also:
  • Explain the contents of 1926.60 (including Appendices A and B) and tell employees where a copy of the standard is available (1926.60(l)(3)(ii)(A));
  • Describe the medical surveillance program required under paragraph (n) and explain Appendix C (1926.60(l)(3)(ii)(B)); and
  • Describe the medical removal provisions required under paragraph (n) (1926.60(l)(3)(ii)(C)).

• Access to materials: Employers must make all written training materials (including a copy of the MDA regulation) readily available to affected employees at no cost (1926.60(l)(4)(i)).

If you need a quick checklist: ensure your workplace labels use the exact required wording, schedule initial and annual training that covers Hazard Communication plus the three MDA‑specific topics above, and keep all written materials available to employees free of charge. (Cited: 1926.60(l)(2)(ii)(B), 1926.60(l)(3), and 1910.1200(h).