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Methylene Chloride Facts No. 10
Suggested Engineering Controls for Vapor Degreasing Operations
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.
Certain workers at facilities that perform open-top and/or conveyorized vapor degreasing operations are at risk of being exposed to high levels of MC. Some 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. 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.
Local exhaust ventilation (LEV) is often the best way to reduce MC exposures to acceptable levels. LEV units capture vapors at the source and remove them from the work area. A typical LEV unit has a metal hood, fan, ductwork, and a make-up air system. Note: A make-up air system is required to ensure the proper operation of the LEV.
If monitoring results indicate that worker exposures to MC are above established limits when working on or near a specific operation, and new or improved controls are necessary, consider using one or more of the following ventilation control options:
Engineering Control Options for Tanks
If monitoring results indicate that worker exposures to MC are above established limits when working near tanks, 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.
Aqueous cleaning can be used as a substitute for some degreasing operations. Aqueous cleaning uses detergents in hot water to remove oil and grease from metal parts. In cases where aqueous cleaning is not effective, some non-chlorinated solvents such as isopropyl alcohol and mineral sprits may work.
Keep in mind that substitutes may also present health and safety hazards to workers. Always select substitutes that reduce hazards, and always refer to the substitute's material safety data sheet to find out about any control measures and protective equipment you must use to protect workers or the environment.
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 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.