- Metal dust such as aluminum and magnesium.
- Wood dust
- Coal and other carbon dusts
- Plastic dust and additives
- Certain textile materials
- Other organic dust such as sugar, flour, paper, soap, and even dried blood.
- Food Products
- Forest and furniture products
- Metal processing
- Tire and rubber manufacturing plants
- Paper products
- Wastewater treatment
- Recycling operations
- Some coal handling and processing facilities
NFPA 654 Code
The most recent version of NFPA 654 requires facilities to take a more performance-based approach to understanding and managing these dust hazards. This standard is very similar to OSHA's earlier Process Safety Management standard and contains many of the same requirements. A few of the similar requirements are process hazard analysis, management of change, training, hot work and mechanical integrity.
Stringent compliance levels:
According to NFPA 654, “Dust layers 1/32 inch (0.8 millimeters) thick can be sufficient to warrant immediate cleaning of the area.” FYI, this is about the diameter of a paper clip wire or the thickness of the lead in a mechanical pencil!
The standard continues to say that “the dust layer is capable of creating a hazardous condition if it exceeds 5 percent of the building floor area. This means if your floor area is 20,000 square feet, a 1,000-square-foot layer of dust throughout the facility would be the upper limit. The practical reality is that there is a zero-tolerance approach to combustible dust buildup in plants.
Critical questions you must answer:
- What is the risk potential for my workplace?
- What are the tolerance levels for the type of dust I have?
- What can be done to best protect employees and assure compliance with regulations?
#1-What is the risk potential for my workplace?
This is the first question that must be answered to understand the hazard at your facility. Safety Links will conduct an initial walk-through along with an evaluation of any existing dust control systems. The walk-through focuses on dust containment practices, design of equipment safeguards (e.g., isolation), existence of explosion protection, grounding and bonding and appropriate electrical classification.
The management systems evaluated will include those recommended by the NFPA 654 (Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids) including process hazard analysis, management of change, training and procedures, hot work, inspection and maintenance.
Afterwards a report will be issued with the results of the preliminary assessment, including key prescriptive safeguard requirements as recommended by applicable codes and standards including the NFPA 654 and OSHA’s guidance documents NEP, CPL 03-00-008.
Where a more comprehensive assessment of the actual dust is necessary (e.g., to meet the new NFPA 654 performance standard) or desired (e.g., where a high level of potentially combustible dust hazard exists), our Safety Professionals can help develop a dust sampling strategy. This strategy will help characterize the dust and provide objective data needed to answer the second question.
#2-What are the tolerance levels for the type of dust I have?
Each dust compound has unique physical and chemical characteristics. A good understanding of both is essential to understand the hazards, and ultimately the risks, associated with the dust being handled. Safety Links has assisted many organization’s with the development of a comprehensive testing plan appropriate for the handling operations being evaluated. By targeting their specific needs, overall testing costs are reduced and safety is improved.
To properly characterize most dusts, testing of an actual process sample is required. This ensures the measured data is representative of the dust present in the process being analyzed. Properly characterizing the dust hazard prevents unnecessary safeguards from being recommended, particularly if the overall risks do not justify the conservative designs many are incorporating.
Depending on the type of process being analyzed and the potential explosion prevention measures to be employed, a testing plan will be selected.
- Minimize the escape of dust from process equipment or ventilation systems
- Use dust collection systems and filters
- Utilize surfaces that minimize dust accumulation and facilitate cleaning
- Provide access to all hidden areas to permit inspection
- Inspect for dust residues in open and hidden areas, at regular intervals
- Clean dust residues at regular intervals
- Use cleaning methods that do not generate dust clouds, if ignition sources are present
- Only use vacuum cleaners approved for dust collection
- Locate relief valves away from dust hazard areas; and
- Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (preferably in writing with established frequency and methods)
If the dust cannot be controlled at the source another option is to control ignition sources.
- Use appropriate electrical equipment and wiring methods
- Control static electricity, including bonding of equipment to ground
- Control smoking, open flames, and sparks
- Control mechanical sparks and friction
- Use separator devices to remove foreign materials capable of igniting combustibles from process materials
- Separate heated surfaces from dusts
- Separate heating systems from dusts
- Proper use and type of industrial trucks
- Proper use of cartridge activated tools
- Adequately maintain all the above equipment
The use of proper electrical equipment in hazardous locations is crucial to eliminating a common ignition source. Once these areas have been identified, special Class II wiring methods and equipment (such as "dust ignition-proof" and "dust-tight") must be used as required by 29 CFR 1910.307 and as detailed in NFPA 70 Article 500. It is important not to confuse Class II equipment with Class I explosion-proof equipment, as Class II addresses dust hazards, while Class I addresses gas, vapor and liquid hazards. The use of industrial trucks is regulated by OSHA’s Powered Industrial Trucks standard (29 CFR 1910.178). Hazardous atmospheres including dust concentrations are addressed in paragraph (c) of this standard.
The final option is Damage Control.
- Separation of the hazard (isolate with distance)
- Segregation of the hazard (isolate with a barrier)
- Deflagration venting of a building, room, or area
- Pressure relief venting for equipment
- Provision of spark/ember detection and extinguishing systems
- Explosion protection systems (also refer to NFPA 69, Standard on Explosion Prevention Systems)
- Sprinkler systems
- The use of other specialized suppression systems