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Methylene Chloride Facts No. 3
Suggested Engineering Controls For Furniture Refinishers
Occupational Safety and Health Administration (1998)
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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.
About 6,590 furniture refinishing establishments use products that contain MC. Many 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.
Monitoring
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 the
OSHA's web site.
Ventilation Systems
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:
- Increase the exhaust capacity of the ventilation system.
- Install a remote electrical switch to turn on the LEV, rather than a switch on the unit.
This way, workers can turn on the LEV without going near the MC.
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.
General (or dilution) ventilation uses fans or open windows to move clean air through
the work area. This does not confine MC vapors to one area, so it usually does not protect
workers as well as LEV. General ventilation can sometimes reduce MC to acceptable levels
in areas used only for minimal manual stripping operations.
- Store MC in closed containers near general dilution ventilation.
- Turn on general ventilation at least an hour before work begins or leave it on
overnight.
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:
- Install a wall-mounted LEV next to all tanks.
- Install an exhaust hood over the tank and/or slot hoods on each side.
- Put a perforated plate about 9 inches from the bottom of each spraying tank with a down
draft ventilation system to pull air through the plate. The plate raises the furniture
being worked on so that the operator does not have to bend over the tank. The plate also
reduces the amount of MC that evaporates from the tank.
- Put a turntable inside the spraying tank so that furniture in the tank can be rotated.
This way the workers can stay in one spot when applying stripping solution. Having the
worker in one spot makes it easier to provide fresh air to the worker.
- When transferring stripping solution from a container to a tank, use a vapor return line
to create a 'closed loop' and contain MC vapors.
- Use long-handled brushes for scrubbing to keep workers as far out of the tank as
possible.
Engineering Control Options for the Rinse Area
If monitoring results indicate that worker exposures to MC are above established limits
when working in or near the rinse area, and new or improved controls are necessary,
consider using one or more of the following control options:
- Install a wall-mounted LEV in the rinse area.
- To make the LEV more effective, isolate the rinse area, by using a curtain or by putting
it in a separate room.
- Install a sneeze shield in the rinse area. This can help to contain the operation and
reduce splashing.
Other Engineering Tips
- Keep dip tanks and spraying tanks in an isolated area (separate from other work areas).
- Use a belt heater to keep stripping solution at the appropriate temperature (often
around 70F). At this temperature, wax in the solution will form a vapor barrier that
prevents the solution from evaporating too quickly. If the temperature is too high or too
low, the wax will not form a vapor barrier.
- Do not use aluminum in any equipment used to handle, store, or process MC. MC corrodes
aluminum. If aluminum parts fail, spills will occur.
- Add a four-inch layer of water on top of the MC in the dip tank to form a vapor barrier.
- Use closed or covered MC containers that can connect to the spraying table. This way, MC
vapors from the containers flow directly into the trough, where the exhaust system can
remove them.
Additional Monitoring
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.
Substitutes
Using furniture stripping solutions that do not contain MC is another way to reduce MC
exposure.
- n-Methyl-pyrrolidone (NMP) can remove clear and pigmented nitrocellulose lacquers,
conventional varnish, and all types of water-borne coatings as well as MC.
- Methanol, acetone, and toluene can remove many finishes and paints. These substitutes
are extremely flammable, so be sure to take appropriate precautions.
Also, using diluted stripping solutions (i.e., 50 percent MC mixture) in conjunction
with other controls such as LEV is a good way to reduce employee exposure. Keep in mind
that substitute stripping solutions 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.
Respirators
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 for 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.
Compliance Schedule
Employers with 1 to 20 employees have until:
- February 4, 1998 to implement paragraph (d) (Initial Monitoring).
- April 10, 2000 to implement paragraph (f) (Engineering Controls).
- April 10, 2000 to implement Respiratory Protection to achieve the 8-hour TWA PEL only.
- April 10, 1998 to implement all other provisions.
Employers with 20 to 49 employees have until:
- September 7, 1997 to implement paragraph (d) (Initial Monitoring).
- April 10, 2000 to implement paragraph (f) (Engineering Controls).
- April 10, 2000 to implement Respiratory Protection to achieve the 8-hour TWA PEL only.
- December 21, 1997 to implement all other provisions.
Employers with 50 or more employees have until:
- September 7, 1997 to implement paragraph (d) (Initial Monitoring).
- April 10, 1999 to implement paragraph (f) (Engineering Controls).
- April 10, 1999 to implement Respiratory Protection to achieve the 8-hour TWA PEL only.
- December 21, 1997 to implement all other provisions.
Additional Resources
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.
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