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 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 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.
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.
Credit to: HazardEx / IML Group plc