The dangers of wood dust
05 February 2010
In the woodworking industry, wood dust not only poses problems to worker health, but also represents an explosion risk, which can have devastating results. It is important for companies to understand these risks and put in place measures to protect their workers.
Wood dust consists of tiny particles of wood produced during the processing and handling of wood, chipboard, and/or hardboard. Worker exposure is high in many industries, including logging and sawmill operations, furniture and paper manufacturing, and construction of residential and commercial buildings. Operations within these industries, such as sawing, routing and turning; sanding, by machine and by hand; and using compressed air lines to blow dust off furniture and other articles before spraying are the most likely to produce high dust levels.
Wood dust in the workplace has several hazards associated with it. Exposure to excessive amounts is considered to have an irritant effect on eyes, nose and throat in addition to pulmonary function impairment and is considered a human carcinogen, with hardwood dust causing cancers, particularly of the nose. Other health effects include dermatitis and/or respiratory effects, such as asthma. Carpenters and joiners are 4 times more likely to get asthma compared with the UK working population. In addition, when a worker becomes sensitised to wood dust, he or she can suffer an allergic reaction after repeated exposures. Wood dust on the floor can cause tripping or slipping. Vision can be impaired by airborne chips and dust generated during wood processing.
Furthermore, each year premises and plant are severely damaged or destroyed by wood dust fires and explosions. Wood dust is considered to be explosive if ignition of part of a cloud of wood dust results in the propagation of flame through the rest of the cloud. The vigour of flame propagation will vary from dust to dust and not all flammable dusts are equally explosive. The burning of an unconfined wood dust cloud produces a flash fire. If the wood dust is contained within a full or partial enclosure, the pressure build up can produce a destructive explosion. Its severity will depend on the type and concentration of the dust, the size of the source of ignition and the strength of the enclosure. Generally, the larger the volume of the exploding dust cloud, the more widespread its effects will be. It is important to ensure that wood dust does not escape from collection systems and be allowed to accumulate within workrooms. If dust does accumulate, any primary explosion which occurs in a collection unit may stir up dust deposits that may have accumulated on walls, floors and ledges which in turn can ignite causing a secondary explosion. Burning particles from the primary explosion can ignite the dust cloud which results from it, leading to a secondary explosion that is usually more destructive than the first.
Wood dust will also burn readily if ignited. Fires can be started by badly maintained heating units, overheated electric motors, electric sparks and sparks from other sources such as open wood burning stoves and cigarettes.
In the USA in July 2009, ready-to-assemble furniture manufacturer Ameriwood was fined $108,700 and cited for six repeat violations and six serious violations stemming from a January 20th inspection of its manufacturing plant in Tiffin, Ohio. Many of the alleged violations involved potential dust hazards, including failure to maintain and install spark detection and suppression equipment in several of the plant’s dust collectors.
In another recent case, OSHA levied more than $255,000 in fines for 60 alleged safety and health hazards against Sturn Ruger & Co. Inc., a manufacturer of firearms based in Newport, New Hampshire. According to OSHA, "safety hazards included the lack of spark detectors or suppression systems to minimise fire and explosion hazards in ventilation systems that collect combustible wood and metal dust, allowing combustible dust to accumulate."
Engineering controls and personal protective equipment are two methods used for controlling wood dust exposure. Engineering controls, the preferred approach, typically includes a local exhaust ventilation (LEV) system with collectors placed at points where dust is produced to extract dust before it can get inhaled. It is important that these extraction and collection systems are maintained to make sure it continues to work efficiently. It is a legal requirement to have dust extraction equipment examined by a competent person at least every 14 months.
A vacuum system to clear up wood dust helps prevent dust accumulations and the risk of secondary explosions if ignition should occur. The use of dry sweeping or airlines should not be used as it may cause high peaks or dust exposure and simply spread the wood dust around.
Personal protective equipment is another short term solution to wood dust exposure. Respirators may be worn to remove hazardous particulates (dusts) and gases. The selection of appropriate respirators requires a thorough knowledge of the workplace, the potential chemical contaminants and their concentrations. The use of respirators also requires implementation of a respiratory protection program. Other personal protective equipment such as eye protection, overalls and gloves should be cleaned regularly.
It is important for woodworking companies to understand the risks discussed and put in place engineered controls and ensure their workers wear the necessary personal protective equipment.
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