Fires and explosions can happen for a multitude of reasons on a construction site but one of the most common causes is combustible dust. Metal-based materials such as aluminum, titanium and steel as well as plastics can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosible. Even materials that do not burn in larger pieces (such as aluminum or iron), given the proper conditions, can be explosible in dust form.
The U.S. Chemical Safety and Hazard Investigation Board (CSB) identified 281 combustible dust incidents between 1980 and 2005 that led to the deaths of 119 workers, injured 718, and extensively damaged numerous industrial facilities. More recently, this year OSHA cited a drilling company for exposing employees to fire and explosion hazards after five employees suffered fatal injuries.
To prevent these deadly dust clouds, safety experts recommend the following precautions:
- Capture dust before it escapes into a work area by using properly designed, installed, approved and maintained dust collection systems.
- Contain dust within equipment, systems or rooms that are built and operated to safely handle combustible dust.
- Clean work areas, overhead surfaces and concealed spaces frequently and thoroughly using safe housekeeping methods to remove combustible dusts not captured or contained.
More specifically:
The dust-containing systems (ducts and dust collectors) should be designed in a manner to prevent leaking so dusts are not allowed to accumulate in the work area.
Construction sites should implement a housekeeping program with regular cleaning frequencies established for floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations within operating areas of the facility.
Separator devices to remove foreign materials capable of igniting combustible dusts should be installed.
Material Safety Data Sheets (MSDSs) for the chemicals which could become combustible dust under normal operations should be available to employees.
Ignition Control Measures
- Electrically-powered cleaning devices such as vacuum cleaners, and electrical equipment need to be approved for the hazard classification for Class II locations.
- Install an ignition control program, such as grounding and bonding and other methods, for dissipating any electrostatic charge that could be generated while transporting the dust through the ductwork.
- Areas where smoking is prohibited should be posted with “No Smoking” signs.
- Duct systems, dust collectors, and dust-producing machinery need to be bonded and grounded to minimize accumulation of static electrical charge.
- Rooms, buildings, or other enclosures have explosion relief venting distributed over the exterior wall of buildings and enclosures.
- Any trucks in an area with the possibility of combustible dust need to be of industrial grade approved for hazardous sites.
- The dust collector systems have spark detection and explosion/ deflagration suppression systems.
For worker training purposes, employees need to be informed on the explosion hazards of combustible dusts and emergency exit routes need to be maintained properly.
Fire safety becomes everyone’s job at a worksite. A fire safety plan should outline the assignments of key personnel in the event of a fire and provide an evacuation plan for workers on the site.
For more information on fire and explosion prevention, contact our offices at Diversified Safety Services.
