Methylene chloride safety guidelines

Under 1910.1052 App A, the permissible exposure limits are 25 ppm as an 8-hour TWA and 125 ppm as a 15-minute STEL. See the Exposure limits stated in 1910.1052 App A for these values.

Under 1910.1052 App A, an employer must offer medical surveillance if an employee is exposed at or above the action level (12.5 ppm 8-hour TWA) for more than 30 days per year or is exposed above either PEL (25 ppm TWA or 125 ppm STEL) for more than 10 days per year. See the Medical surveillance requirements in 1910.1052 App A.

Under 1910.1052 App A, only MSHA- or NIOSH-approved supplied-air respirators are permitted because air-purifying respirators do not provide adequate protection against methylene chloride. The appendix also requires a written respiratory program with training, maintenance, inspection, cleaning, and evaluation. See the Respirator guidance in 1910.1052 App A.

Under 1910.1052 App A, workers should not rely on smell because methylene chloride has poor and variable odor warning properties and people can adapt to its odor. The appendix explicitly states odor thresholds vary widely and odor is not an adequate warning. See the Warning properties discussion in 1910.1052 App A.

Under 1910.1052 App A, immediately move the exposed person to fresh air; if breathing has stopped, perform cardiopulmonary resuscitation (CPR); keep the person warm and at rest; and get medical attention as soon as possible. The appendix also says to notify medical/rescue personnel and follow your facility's emergency rescue procedures. See the Emergency first aid procedures in 1910.1052 App A.

Under 1910.1052 App A, employers must provide impervious clothing, gloves, face shields (minimum eight-inch), and splash-proof safety goggles when there is potential for liquid methylene chloride contact; employees must be required to use them to prevent repeated or prolonged skin contact. Contaminated clothing must be handled in a designated regulated area before laundering or disposal. See the Protective clothing and eye protection guidance in 1910.1052 App A and hygiene provisions referenced to 1910.141.

Under 1910.1052 App A, emergency drench showers and eyewash facilities are recommended where there is potential for liquid methylene chloride contact and they should be maintained in sanitary condition. Employers should also provide suitable cleansing agents for skin decontamination. See the Housekeeping and hygiene recommendations in 1910.1052 App A and the general hygiene standard at 1910.141.

Under 1910.1052 App A, employers must take representative breathing-zone measurements using methods such as charcoal adsorption tubes analyzed chemically, OSHA Method 80, or validated real-time instruments or dosimeters, ensuring the chosen method meets the accuracy requirements specified in the standard. The appendix also requires sampling to cover the full shift for 8-hour evaluations and that monitoring be done by a technically qualified person. See the Monitoring and measurement procedures in 1910.1052 App A.

Under 1910.1052 App A, monitoring methods must be accurate to a 95 percent confidence level to ±25% for concentrations at or above 25 ppm and to ±35% for concentrations at or below 25 ppm. OSHA Method 80 is cited as an example of a validated method. See the Monitoring accuracy requirements in 1910.1052 App A.

Under 1910.1052 App A, employees or their designated representatives have the right to observe the monitoring procedure, record the results, and must be provided protective equipment if monitoring occurs in areas where such equipment is required. The appendix explains that observation includes seeing the steps taken in the measurement procedure and recording the results. See the Observation of monitoring and employee rights in 1910.1052 App A.

Under 1910.1052 App A and the Hazard Communication standard, employers must provide labels and safety data sheets for all materials, mixtures, or solutions that contain more than 0.1% methylene chloride; these items must be classified and labeled in accordance with 1910.1200. The appendix gives sample label wording and hazard statements for methylene chloride-containing products. See the labeling and SDS requirements in 1910.1052 App A and 1910.1200.

Under 1910.1052 App A, when methylene chloride spills occur remove ignition sources, ventilate the area, restrict access to people without protective equipment, collect for reclamation or absorb with vermiculite/dry sand/earth, and for small spills absorb and allow safe atmospheric evaporation; large quantities should be incinerated in scrubbed systems. The appendix also recommends a leak and spill detection program. See the Spill and housekeeping guidance in 1910.1052 App A.

Under 1910.1052 App A and the hazardous location guidance, electrical installations in areas classified as hazardous due to methylene chloride must be treated as Class I locations and electrical equipment must be suitable for atmospheres containing methylene chloride vapors in accordance with 1910.307. The appendix specifically states locations with MC should be Class I per Article 500 of the National Electrical Code and installed per Article 501. See the Electrical equipment and Class I location guidance in 1910.1052 App A and 1910.307.

Under 1910.1052 App A, contaminated protective clothing must be removed in a designated regulated area, kept in that area until methylene chloride has evaporated, and then laundered or disposed of appropriately; clothing wet with methylene chloride should be removed immediately and not re-worn until found fit for reuse. See the Contaminated clothing procedures in 1910.1052 App A.

Under 1910.1052 App A, employers must keep records of employee exposure measurements and medical examinations and retain them for at least 30 years; employees or their representatives must be able to obtain these records on request. See the Recordkeeping and access to information in 1910.1052 App A.

Under 1910.1052 App A, methylene chloride should be stored in plain, galvanized or lead-lined mild steel containers in a cool, dry, well-ventilated area away from direct sunlight, heat, and other acute fire hazards; usual shipping containers include glass bottles, 5- and 55-gallon steel drums, tank cars, and tank trucks. See the Storage recommendations in 1910.1052 App A.

Under 1910.1052 App A, when methylene chloride is involved in fire it can emit highly toxic fumes such as phosgene, hydrogen chloride and carbon monoxide, so firefighters must wear breathing apparatus and use water spray to keep containers cool; acceptable extinguishing media include dry chemical, carbon dioxide, and foam. See the Firefighting guidance and hazard statements in 1910.1052 App A.

Under 1910.1052 App A, employees should not keep food, beverages, or smoking materials, nor eat or smoke in regulated areas where methylene chloride concentrations are above the permissible exposure limits. See the Workplace hygiene prohibitions in 1910.1052 App A.

Under 1910.1052 App A, recommended controls include process enclosures, local exhaust ventilation, chilling coils and substitution for vapor degreasing; for paint and furniture stripping, general dilution ventilation, local exhaust, personal protective equipment and substitution are recommended. The appendix lists controls for common operations in a concise table. See the Operations and controls table in 1910.1052 App A.

Under 1910.1052 App A, methylene chloride is unstable with heat and moisture and can react dangerously with strong oxidizers, caustics, and chemically active metals (e.g., aluminum, magnesium powder, sodium, potassium), which can cause fires or explosions; it also attacks some plastics, rubber, and coatings. Employers should avoid these combinations and store/handle MC accordingly. See the Reactivity hazards in 1910.1052 App A.

Under 1910.1052 App A, employers should keep the workplace clean and sanitary, institute leak and spill detection, provide cleansing agents to remove methylene chloride from skin, and designate regulated areas for removal of contaminated clothing; emergency showers and eyewash stations are recommended. These practices support compliance with 1910.141 on sanitation. See the Housekeeping and hygiene guidance in 1910.1052 App A.

Under 1910.1052 App A, employers must inform employees of the information in the appendix, instruct them in proper work practices, emergency procedures, correct use of protective equipment, inform employees of monitoring results, actions taken to reduce overexposure, and make exposure and medical records available on request. See the Access to information and training requirements in 1910.1052 App A.

Under 1910.1052 App A, the appendix notes that it addresses methylene chloride exposure in marine terminal and longshore employment only where leaking or broken packages allow exposures not already covered by compliance with 29 CFR parts 1917 and 1918; employers in those sectors must follow the marine-specific parts as applicable. See the Marine terminal/longshore note in 1910.1052 App A.