Methylene Chloride Facts No. 7
Suggested Work Practices for Flexible Polyurethane Foam Manufacturers

Occupational Safety and Health Administration

On January 10, 1997, the Occupational Safety and Health Administration (OSHA) issued a standard that lowered the limit on worker exposures to methylene chloride (MC). This new standard greatly reduces the chance of developing health problems from working in facilities that use MC.

Worker exposures to MC occur mainly through breathing its vapors. MC can also pass through workers' skin if it gets on their body or clothes. Occasionally, workers can swallow small amounts of MC if they don't wash their face and hands before eating, or if they eat in contaminated work areas. Short-term exposure to high levels of MC can cause dizziness, headaches, a lack of coordination, and irritation of the skin, eyes, mucous membranes, and respiratory system. Long-term exposure causes cancer in laboratory animals. Studies in workers suggest an association between MC exposures and certain types of cancer. OSHA considers MC to be a potential occupational carcinogen. Exposure to MC may also make the symptoms of heart disease (e.g., chest pains, angina) worse.

Many flexible polyurethane foam (p-foam) manufacturing facilities use MC as a blowing agent to make soft foam. Most p-foam manufacturing facilities use engineering controls to lower MC levels. However, at many facilities improving work practices and housekeeping procedures can greatly reduce exposures to MC. The following suggested practices may help you reduce your workplace exposures.

Keep MC Vapors Contained

  • Keep the doors to the pouring and cooling areas closed at all times.
  • Store and transport MC only in approved safety containers.
  • Properly label all MC containers to indicate their contents, hazards, and proper use, storage, and disposal. Read these labels and follow the directions.
  • Keep MC containers closed tightly when not in use.
  • Avoid unnecessary transfer or movement of MC.
  • Keep the openings on the sides of the tunnel closed when it is not in use. This keeps MC vapors from escaping and ensures that the makeup air system at the end of the tunnel runs well.

Avoid Breathing MC Vapors

  • Turn on local exhaust ventilation systems in the tunnel and cooling rooms at least an hour before work begins or leave them on overnight.
  • Turn on the general ventilation system in the cooling room at least an hour before work begins or leave it on overnight.
  • Avoid breathing air directly above cooling foam.
  • When possible, minimize the amount of time spent near the cooling foam and tunnel openings because these areas are likely to have the highest levels of MC vapors.
  • Do not work or stand between cooling foam and the exhaust system.
  • Do not rely on the odor of MC to warn you of overexposure. People cannot smell MC until vapor concentrations are above 300 ppm, which is 12 times higher than the 8-hour time-weighted average permissible exposure limit of 25 ppm. Also, your sense of smell can quickly get used to the odor of MC so that you stop noticing it.
  • If you become dizzy, light-headed, or have other symptoms of MC exposure, go immediately to an area with fresh air.

Avoid Direct Skin Contact with MC

  • Wear two pairs of gloves when using MC. The inner glove should be made of polyethylene (PE)/ethylene vinyl alcohol (EVOH), PE, or laminate to prevent MC penetration. The outer glove should be made of nitrile or neoprene to protect against puncture or rips. [Note: Because MC can readily penetrate nitrile and neoprene, wearing just the outer glove will not protect your skin from MC exposure.]
    • Wear shoulder length gloves, or the longest gloves possible.
    • Before use, inspect gloves for pin-holes, cracks, thin spots, softening, swelling, and stiff or sticky surfaces.
    • Change gloves frequently, before breakthrough occurs.
    • Rotate several pairs of gloves throughout the day.
    • Let gloves dry in a warm, well-ventilated area at least overnight before reuse.
  • Wear rubber aprons and boots or shoe covers to prevent MC from getting on your clothes which results in prolonged skin contact with MC.
  • Wear a face shield or goggles to protect your face and eyes.
  • Use the washing facilities in your work area to wash off any MC from your hands and face.
  • Use lots of soap or mild detergent and water to clean grease, oil, dirt, or anything else off your skin. Do not use MC or other organic solvents to clean your skin.

Minimize the Chance of Spills and Leaks

  • Develop and follow your facility's procedures for detecting MC leaks from process equipment, holding tanks, and spill control devices.
  • Frequently inspect the tunnel and other equipment for cracks, loose parts, and other possible sources of MC leaks.
  • Clean up all spills and leaks as quickly as possible.
  • Place rags, waste, paper towels, or absorbent used to clean spills in a closed container (preferably a non-aluminum, all-metal safety container) immediately after use.
  • Make sure that leaks are repaired and spills cleaned up by employees who are trained in proper cleanup methods. These employees should wear appropriate personal protective equipment (PPE).

Take Extra Precautions in Low and Confined Spaces

MC vapors are heavier than air, so they tend to move to low, unventilated spaces.

  • Do not enter or lean into a low-lying confined area until it has been completely aired out and tested. Wear proper PPE and follow the appropriate confined space entry procedures outlined in OSHA's Permit Required Confined Spaces standard (29 CFR 1910.146).
  • Use a long-handled tool to pick up items that you drop into a confined space or low-lying area.

Take Personal Precautions

  • After working with MC, always wash your face and hands before eating.
  • Never eat in the work area or your food and drink could become contaminated with MC.
  • Avoid drinking alcohol before or after being exposed to MC. Alcohol can lower the amount of MC needed to cause health problems.
  • Be alert when working with MC. Avoid situations that might result in overexposure.

Respirators

If engineering controls and work practices do not reduce MC exposures to an acceptable level, workers must wear supplied-air respirators. Respirators are the least preferred method for controlling employee exposure. Supplied-air respirators must have a clean air supply through the use of compressed air tanks containing air meeting at least the requirements for Grade D breathing air, or a breathing air type compressor with the air intake located in an area with a clean air supply.

CAUTION: Filter cartridge respirators cannot be used because MC can pass through available cartridges leaving respirator wearers unprotected.

Additional Resources

Visit the On-Site Consultation Program page for information on how to request a free, confidential visit from a consultant to help identify ways to improve safety and health at your workplace.