As woodworkers, we have a responsibility to manage our wood waste. The NFPA (National Fire Protection Association) 664 standard, “Wood processing and Woodworking Facilities,” has been around for years. However, new requirements in NFPA 652 “Standard on the fundamentals of Combustible Dust” take effect in September and therefore require immediate attention. I have been working with a number of wood products manufacturers and noticed that very few in our industry know of this standard.
We get a lot of attention in our industry for combustible dust, and it all boils down to good housekeeping. I get it, I’ve been there – we never have enough time to do good housekeeping, but as a manufacturer using fully automatic and/or manual equipment– all of which with the potential to generate wood dust, there are some key facts you need to know.
NFPA 652 & DHA
As defined by NFPA “combustible dust” is “A combustible particulate solid that presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentration, regardless of particle size or shape.”
Development of the NFPA 652 standard for combustible dust began in 2012. The main objective is to have manufacturers evaluate the potential of fire from combustible dust in the form of a “Dust Hazard Analysis.” As an owner, you are responsible for a DHA of your facilities. The deadline for this is Sept. 7, 2020. This is not a difficult evaluation but, does require your attention.
The key requirements for this NFPA 652 are:
4.1 requires that the “Owners and operators of a facility…shall be responsible.”
5.1 requires hazard identification of materials.
7.1.1 requires a DHA for all existing and new processes.
7.1.2 have a DHA on file by Sept. 7, 2020.
7.1.4 states the DHA must be updated every 5 years.
7.2.2 states that “the DHA must be performed or led by a qualified person.”
What does this really mean to us? You as a woodworker must evaluate your dust and determine which process is hazardous, provide a solution to eliminate or mitigate the hazard, and have a plan of action in case of an emergency.
The goal is to eliminate the risk of injury or death from a combustible dust explosion. Key events needed to create this hazard are Fuel, Ignition, Oxygen, Confinement and Dispersion. As responsible woodworkers, our focus needs to be on the fuel. We need to keep the fuel (wood dust) off elevated horizontal surfaces and be diligent with housekeeping.
How to perform a DHA
Each manufacturing process needs to be evaluated – including work cells. Keep in mind that dust collection is also considered a process. Although the actual process of developing the DHA is simple, if you do not have the time or are not comfortable with doing this, there are plenty of resources available to help.
We have developed a checklist for woodworkers to evaluate their facilities. Developing your own DHA has numerous advantages, but the most important is that this process allows you to see dust in a different light.
1. The DHA process starts with the evaluation of your dust, taking a sample of your material, and having it tested. Based on the Kst (deflagration index/measure of potential explosiveness), combustible dust is ranked into one of four classes: ST0, ST1, ST2, ST3. Unless you have special circumstances, you can expect to be categorized as ST1 (Kst <200). Most woodworkers have a Kst of 100-200, so yes, you have combustible dust. It is important to note, even a low Kst level/weak dust explosion class can cause significant damage, injury or even death.
2. Do you have an ignition source? For your DHA process assume the answer is yes. Since no one knowingly allows open flames in the woodshop, assume that if there is a spark it will occur by accident, and you can’t plan when and how this happens.
3. Do you have dust in sufficient quantity to be explosive? This is dependent upon the MEC (Minimum Explosible Concentration) of your process. Typical woodworking dust collection ducting does not have enough concentration to produce an explosion (40g/M3). However, this can also depend on the type of wood waste; is it a chip or fine powder? Is there a high volume of wood dust generated at the process or machine? For example, edgebanders do not typically have the same risk as a CNC router or sander.
Particular areas of high-risk are the dust collector and transport line. There are many variances to dust collection systems, and some are higher risks than others. If you are unsure, you need to ask. Spark detection systems can help minimize risk.
4. Is dispersion possible? Is there dust sitting on surfaces which can be disturbed and create a dispersion? This can happen when the dust collection is not sufficient, and operators use compressed air to clean surfaces. You have to identify these areas and create a plan to keep them clean.
Once you identify these problem areas, you need to develop internal processes to eliminate and monitor. This may include vacuuming versus blowing dust, increasing the cleaning of fugitive dust, evaluation of dust hoods, dust collection, or solutions for ceiling cleaning. ✚
The NFPA standards for combustible dust that pertain to woodworking include:
NFPA 652: Standard on the Fundamentals of Combustible Dust, 2019 Edition
NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities, 2020 Edition
NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, 2020 Edition
NFPA 68: Standard on Explosion Protection by Deflagration Venting, 2018 Edition
NFPA 69: Standard on Explosion Prevention Systems, 2019 Edition
For more information visit NFPA.org.
Have something to say? Share your thoughts with us in the comments below.