Hazards/Solutions Potential Hazards: Both the skin and respiratory system can become sensitized to wood dust. A worker who becomes sensitized to wood dust can suffer a severe allergic reaction such as asthma after repeated exposure or exposure to lower concentrations of the dust. Other common symptoms associated with wood dust exposure include eye irritation, nasal dryness and obstruction, prolonged colds, and frequent headaches. Certain species of hardwood—such as oak, mahogany, beech, walnut, birch, elm, and ash— have been reported to cause nasal cancer in woodworkers. This is particularly true when exposures are high. The American Conference of Governmental Industrial Hygienists (ACGIH) recognizes wood dust as a "confirmed" human carcinogen, and recommends a limit of 1 milligram per cubic meter (mg/m 3 ) for hardwoods and 5 mg/m 3 for softwoods. At this time, OSHA regulates wood dust as a nuisance dust; however, OSHA strongly encourages employers to keep exposures to a minimum and to adopt the ACGIH levels. The maximum permissible exposure for nuisance dust is 15 mg/m 3 , total dust (5 mg/m 3 , respirable fraction). Possible Solutions: Engineering Controls Wood dust is emitted at high velocity by moving or spinning machine components. The primary method of controlling wood dust is with local exhaust ventilation (LEV), which removes dust at or near its source as shown in the two figures to the right. LEV systems can often be integrated with machine guards. Exhaust hoods should be located as close as possible to the emission source, either on the woodworking machinery itself or near to the machine. The local exhaust systems should have an efficient air cleaning device. For LEV systems to provide maximum protection, they should be properly maintained. Check and clean ducts and dust collectors at regular intervals. Inspect ducts to ensure that they are not loose, broken, or damaged. Check the V-belts on the drive units of belt-driven exhaust fans for slippage or breakage. Make sure the duct velocity is maintained at a minimum of 2,500 to 4,000 feet per minute to effectively remove light, dry saw dust, heavy wood chips, and green shavings, and to prevent these from plugging the system. Fig. 31a Local Exhaust Hood for Table Saws. Fig. 31b Local Exhaust Hood for Table Saws. Sanders, shapers, and routers generally produce the greatest amount of dust. Conventional means for exhausting these machines are not very effective. The National Institute for Occupational Safety and Health (NIOSH) has developed new, innovative means for controlling dust exposure from these machines, but these methods are not yet commercially available. These methods either increase the exhaust volume or velocity, or supply pressurized air to help blow dust particles from the machine into an exhaust hood. Improved hood configuration for shapers. Work Practices See the control of fire and explosion hazards section for information on work practices to control dust accumulations.

 

LEV Recommendations Circular Saws Band Saws Jointers Shapers Planers/Moulders Lathes Sanders Routers   Circular Saws Exhaust the saw through the bottom of the table. Provide LEV under the blade slot. To decrease the open area between the table and the lower hood, attach a strip of flexible material to the machinery that will cover this area when the hood operates. Add a local exhaust hood above the top of the saw blade to increase dust control. Be sure the hood is integrated with the guard on the upper part of the blade. Consult the NIOSH Hazard Controls HC10 for more information on control of wood dust from circular and other kinds of table saws. Band Saws Provide LEV under the blade slot. To increase the collection area of the hood, add holes (1/8 inch in diameter) in the table around the slot area. Place a suction nozzle above the table, at the rear of the saw blade to collect wood dust from the saw teeth. Jointers Place a hood underneath the machine head. Shapers Control each head with an open-faced hood, located on the table behind the head. For additional protection, use a combination of fixed and adjustable hoods. A fixed open-faced hood can be attached to the rear of the table between the shaper heads. Movable open-faced hoods also can be used on the table. For further information please consult the NIOSH Hazard Controls HC5: Wood Dust from Shapers. Planers/Moulders Place open-faced hoods above the spinning heads of planers. Each head can be ventilated separately, or one hood can be used to control several heads. Place open-faced hoods around the spinning components of moulders. Each head should be separately controlled. Add a small open-faced hood along the side of the moulder between the main head and the worker for increased dust control. Lathes Place an open-faced hood attached to a movable mechanical arm at the point of operation. Sanders Sanders produce a considerable amount of dust and are difficult to control. Conventional methods do not effectively remove dust. New innovative systems have been developed for controlling dust emissions from horizontal belt sanders, large-diameter disc sanders, random orbital hand sanders, and orbital hand sanders. Although these systems are not yet commercially available, NIOSH can provide more information. The following NIOSH Hazard Controls deal with horizontal belt sanders, large diameter disc sanders, random orbital hand sanders, and orbital hand sanders respectively: HC4, HC 7, HC 8, and HC 9. Some of these systems are discussed below. Enclose disc sanders with an exhaust hood, installed below the table; cover the back of the sanding disc at points above the worktable. A system has been developed that supplies pressurized air to the disc inside the hood. The jet of high speed air blows dust particles out of the disc air layer so they can be captured by the exhaust hood. On random orbital sanders, use an aspirator in combination with a perforated sanding pad. The aspirator creates a vacuum that draws wood dust up through the holes of the sanding pad. An innovative dust control system has been developed that uses additional exhaust and a slotted sanding pad. A new dust control plenum has been designed for orbital sanders shown in the two figures to the right. The plenum fits between the sanding pad and the sander body and has a series of exhaust slots along its edges. Enclose horizontal belt sanders with exhaust hoods covering each end of the belt. These hoods control the dust carried by the belt. To control dust emissions further, install an additional hood above the area where the wood is processed. To increase the effectiveness of this system, add a narrow hood and a stripper. Routers Place two open-faced hoods behind the heads of the router table. Connect the hoods to the exhaust ductwork via a flexible hose. Locate an open-faced or slot hood at the rear end of the router table. NIOSH has published a series of "Hazard Controls" concerning wood dust control techniques. For details see the Additional References section of this eTool.

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