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Methylene Chloride Facts No. 6
Suggested Engineering Controls for Flexible Polyurethane Foam Manufacturers
Occupational Safety and Health Administration (1998)
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 facilities that manufacture flexible polyurethane foam (p-foam) use MC as a blowing agent to make soft foam. Most of these facilities will need to use engineering controls to reduce worker exposures to MC to acceptable levels. The following describes some engineering controls that you may find helpful in reducing worker exposures to MC in your facility.
Employers must monitor worker exposures to MC to determine whether engineering controls are necessary. Where engineering controls are already in place, employers must monitor worker exposures to determine the effectiveness of the controls and whether or not improvements or additional control methods are needed. The revised standard published on September 22, 1998 (FR 63; 50712-50732) contains additional STEL monitoring requirements for those specific industries taking advantage of the extended compliance dates. For additional information on monitoring for MC, see OSHA Methylene Chloride Facts No. 01 or OSHA's Chemical Sampling Information which is accessible through OSHA's web site.
Worker exposures to MC are highest near the tunnel where p-foam is made. MC vapors come from the front end of the tunnel where the raw materials are poured and mixed, from the bottom end of the tunnel where the foam is cut, and from leaks and openings in the tunnel. Most tunnels have local exhaust ventilation (LEV) units.
Note: Check with the appropriate local, county, or state environmental office to make sure you have the required permits if you will be exhausting MC directly outside.
If monitoring results indicate that worker exposures to MC are above established limits when working near the tunnel, and new or improved controls are necessary, consider using one or more of the following control options:
The saw operator is often exposed to high levels of MC, so additional controls may be necessary to protect these workers. If monitoring results indicate that saw operator exposures to MC are above established limits, and new or improved controls are necessary, consider using one or more of the following control options:
As the foam cools, it releases MC. Most MC is released during the first few hours of cooling. If monitoring results indicate that worker exposures to MC are above established limits when working in or near the cooling area, and new or improved controls are necessary, consider using one or more of the following control options:
Always remember to monitor worker exposures again after you install new engineering controls to determine whether the controls are working properly and reducing exposures to acceptable levels.
Using blowing agents other than MC is another way to reduce MC exposure.
If engineering controls and work practices do not reduce MC exposures to an acceptable level, you must give workers supplied-air respirators. Respirators are the least preferred method of controlling employee exposures. 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.
Employers in p-foam manufacturing with less than 20 employees have until:
For more information concerning consultation assistance, contact the nearest OSHA office (look under state listings for the Department of Labor), refer to the listings on OSHA's web site, or contact OSHA's Office of Information at (202) 219-8151.