Understanding NFPA Standards for Wood-Product Manufacturers

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Come September 2020, wood product manufacturers must complete a dust hazard analysis, as required by NFPA 652. This analysis requires manufacturers to identify fire, flash fire, and explosion hazards and manage those hazards according to NFPA standards. More than a few updates have been made in the 2019 edition of NFPA 652 and the 2020 edition of NFPA 664, which sets forth standards for wood-product manufacturers, so it’s likely your operation will have to make changes to comply.

To familiarize you with current regulations, we’ve provided this short guide to NFPA 652 and 664 related to material handling equipment. This guide is not comprehensive. Please take the time to review the NFPA 652 and 664 standards, which are available online for free at NFPA.org (downloadable copies are available for purchase).


NFPA 652 – 2019 Edition: What You Need to Know

NFPA 652 outlines the National Fire Protection Agency’s standards for combustible dust. It is this standard that requires owners/operators to complete a dust hazard analysis by September 2020. In this analysis, owners/operators must:

  1. Identify and evaluate the processes and facilities in which fires, flash fires, and explosion hazards exist, and
  2. Where hazards exist, identify and evaluate fire and deflagration scenarios, identify what safeguards are in place, and recommend additional safeguards with a plan for implementing them.

NFPA 652 explicitly states that the owner/operator is responsible not only for the analysis but for implementing safeguards. NFPA 652 does not provide a loophole that will allow operations to create a plan but not see it through. The standard specifically says owners/operators are responsible for the following:

  1. Determining the combustibility and explosibility of materials the organization handles.
  2. Identifying fire, flash fire, and explosion hazards.
  3. Managing the identified hazards.

What NFPA 652 Says about Equipment and Facility Safety

NFPA 652 requires that facilities and equipment therein be designed to mitigate fires, flash fires, and explosions that can damage neighboring properties, injure personnel, damage equipment, or damage structures. The standard states that fires and explosions must be isolated—they mustn’t be allowed to move from system to system without check.

The standard also requires all enclosed equipment to contain dust. The requirement does not require manufacturers to install IP-rated “dust-tight” machinery, but it is unclear precisely what the code requires regarding the system as a whole. In NFPA 664, it states, “Access hatches and removable equipment covers shall be tight fitting and securely fastened for dust-tight operation” (, with an explanation in the appendix that states, “Gaskets or smooth machined mating surfaces are generally required for dust-tight operation” (A. NFPA 652 similarly states, “Coverings on cleanout, inspection, and other openings shall be fastened to prevent the escape of combustible dust” ( This implies dust-tight operation, but it is only in reference to openings other than inlets and outlets. Regarding these systems as a whole, NFPA 652 states, “All components of enclosed systems that handle combustible particulate solids shall be designed to prevent the escape of dust, except for openings intended for intake and discharge of air and material” ( This sounds similar to the requirements for openings,but the language is slightly different. What the code means by, “shall be designed to prevent the escape of dust,” is not explained. The requirement for conveyors as a whole may be less stringent than “dust-tight,” but then again, it may not.

The language is further made ambiguous by code in NFPA 664, which states, “All equipment shall be designed to minimize fugitive dust emissions from the equipment.” Here, no mention of a dust-tight design is made, and it seems to allow for some dust to escape the machinery. However, it may be worded this way to allow for the use of dust-collection systems when dust containment cannot be achieved. The appendix note for in NFPA 664 describes how dust collection vents can place negative pressure on the equipment’s interior to minimize dust emissions.

While the technical details of what these codes look like may be unclear, it is clear, however, that the NFPA does not want dust leaking from conveyors. Conveyors that shed sawdust will be deemed unacceptable hazards.

In terms of fire protection, NFPA 652 states that operations must have a means to extinguish the fire, whether the means be manual or automatic. However, automatic systems are required if fighting the fire manually would pose an unacceptable risk to personnel or would not effectively address the fire.

Due to the language in the standard, automated systems may therefore be necessary for enclosed conveyors, as crews cannot reach fires within the conveyors, nor can they reach those fires without removing panels and exposing themselves to the flames.

The NFPA 652 has other requirements for enclosed conveyors, too:

  • Housings must be composed of metal and prevent dust from escaping.
  • Coverings on cleanout, inspection ports, and other openings must not allow dust to escape.
  • Coverings on cleanout, inspection ports, and other openings must be able to withstand an explosion.
  • Conveyors must be equipped with a device that powers off the motor and alerts personnel when the conveyor plugs.
  • The owner/operator must monitor the heat of bearings directly exposed to combustible dust or which accumulate dust unless a risk assessment determines this unnecessary.
  • Enclosures and interconnections must withstand explosion pressures without becoming structurally compromised (for conveyors and other equipment that would allow for an explosion with a volume greater than 8 cubic feet).

NFPA 664 – 2020: What You Need to Know

NFPA 664 builds on NFPA 652 and provides additional standards for preventing fires and explosions in wood processing and woodworking facilities.

The first thing you should be aware of is that, according to 664, a deflagration hazard exists at your facility by definition if you haven’t completed a dust hazard analysis. This means the fire marshal can shut you down, and insurance companies can cancel your coverage even if you have a perfectly safe operation—just because you haven’t completed your analysis.

The second thing you should be aware of is what NFPA 664 states regarding dust accumulation. According to the standard, dust must not be in the air for a deflagration hazard to exist. It need only be present. 664 states in section, “A deflagration hazard shall be deemed to exist in a building compartment when the layer of accumulated fugitive deflagrable wood dust averaged over all upward-facing surfaces in the building compartment exceeds 3.2 mm (1∕8 in.) in thickness.” Dust accumulating on surfaces poses an explosion hazard, and dust collection systems must do their jobs effectively to keep it off surfaces.

Like NFPA 652, 664 requires manufacturers to limit the spread of fires and explosions. This means they must design their processing systems to prevent fire or explosion from spreading from equipment to the interior of buildings or other systems. The code furthermore states that equipment mustn’t allow dust to accumulate within it to the degree that if “half the dust were suspended in a cloud,” it could cause an explosion if ignited ( Dust cannot, therefore, cannot be allowed to accumulate in an elevator boot, for example.

Where 664 goes far beyond 652 is in chapter nine, a nearly-new chapter added in the 2020 edition that details codes for equipment, specifically, “all pneumatic systems, dust control systems, mechanical conveyors, all mechanical equipment of all types used to convey, resize, pulverize, dry, or otherwise process wood and wood-derived particulate and other cellulosic materials used as a substitute or supplement for wood” (9.3.1). This chapter states:

  • Fire protection and explosion mitigation systems must be provided where required.
  • All mechanical conveying systems must be designed, installed, operated, and maintained to avoid excessive heat buildup.
  • Bearings and bushings must be dust tight.
  • Bearings and bushing should be outside the equipment unless the design makes it impractical.
  • Shaft seals must be provided where shafts penetrate equipment walls.
  • All mechanical conveying systems must minimize fugitive dust emissions.
  • Enclosed conveyors must withstand the maximum unvented deflagration pressure of the material being conveyed.
  • Enclosed conveyors must be protected by a deflagration mitigation system when there’s a risk for explosion.
  • Enclosed conveyors indoors must vent through flameless venting systems when there’s a risk for explosion.
  • All access hatches and removable covers must withstand deflagration.
  • Conveyor systems with explosion hazards must be able to be isolated from upstream and downstream so fire does not propagate to other equipment.

Along with these requirements, 664 9.4.11 states:

  • All wood stock must be inspected for foreign materials prior to processing.
  • All foreign materials must be prevented from entering process equipment.

These last two points regarding inspection essentially require wood processors to screen incoming materials mechanically. While the code does not specify how mills must accomplish this, companies processing wood cannot effectively inspect a trailer load of chips by hand, for example. Facilities that do not have screening systems may be forced to invest in these systems to comply with safety standards.


The NFPA will no longer tolerate dusty, hazardous environments in the wood industry, nor will insurance companies. Come September, delays will no longer be acceptable. The time has come to adapt. Are you ready?

If you’re concerned about whether your equipment is up to NFPA standards, call us. We’ll work with you to identify solutions and get your dust under control to comply with NFPA rules. Our SMART Conveyors™ and other material-handling equipment are up to the task, and so are we. Contact us today.

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