HID 6
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In motorcycle and marine outboard engines with multiple carburetors, the vacuum pressure of each carburetor should be balanced. Mechanics commonly use mercury carburetor synchronizers for this procedure. Exposure to mercury may occur in two ways. Mercury carburetor synchronizers (gauges) contain about 40grams of mercury that can be spilled if these gauges are not handled or stored properly. Also, improper engine tuning can cause mercury to be sucked into the engine and released instantly in high concentrations from the exhaust system. Acute exposure to high concentrations of mercury vapor can affect lung function and possibly damage the lungs. Mercury can also enter the body through the skin. Prolonged exposure to mercury can damage the kidneys and the central nervous system.
The National Institute for Occupational Safety and Health (NIOSH) is also concerned that many motorcycle and marine mechanics work in garages without effective ventilation systems for controlling motor vehicle emissions. To reduce exposure to these emissions, the mechanics rely on natural ventilation from open doors and windows, or they try to limit the amount of time an engine runs inside the garage.
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Motorcycle service garages should be equipped with an engine exhaust ventilation system to control carbon monoxide and other contaminants. Also referred to as exhaust collectors, these fan-powered systems are placed either overhead or under the floor, and are connected to flexible ducts that the mechanic attaches to the vehicle tail pipes. Marine mechanics should tune outboard motors in water tanks equipped with a slot exhaust ventilation system placed at the rear of the tank. Drawings and design specifications for these ventilation systems are available from the American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio.
Work PracticesTwo types of mercury-free instruments are available for synchronizing carburetors: analog gauges (also known as vacuum gauges) and electronic gauges. Both of these are more expensive than mercury gauges, which cost $30 to $50. Vacuum gauges cost about $100, and electronic gauges cost $330. However, the proper cleanup and disposal of spills from mercury gauges can be expensive. The EPA requires that mercury from nonresidential spills be treated as hazardous waste by a licensed waste disposal company.
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To obtain more free information about controlling this hazard, or to obtain information about other occupational safety and health issues:
call NIOSH* at
1-800-35-NIOSH (1-800-356-4674), or visit the NIOSH Homepage on the World Wide Web at |
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The principal contributors to this publication were Steven A. Lee, CIH, and Jerome Flesch, MS, of NIOSH; and Lyle E. McKenzie of the Colorado Department of Health. Desktop publishing was provided by Kristina Dragon and Susan Kaelin.
June 1999 DHHS (NIOSH) Publication No. 99-111