Wood dust burns, and when a layer of it is shaken into the air inside a building, it can explode. In a sawmill or planer mill the first flash is often small, at a chipper, a conveyor transfer or a dust collector, but the shock knocks down the dust that has settled on beams, ducts and light fixtures, and that second cloud is what destroys the building. A combustible dust inspection walks the mill zone by zone looking at exactly that: how much dust has escaped, where it has settled, what could light it, and whether collection and cleanup are keeping up. This template records the walk one zone at a time and turns heavy buildup, ignition next to dust and collection that is down into findings. Fill it in here and download a PDF without an account, or speak while you walk, and the document writes itself.
Dust at the machine, and dust that got away
Every saw, planer head, chipper and transfer point makes dust. While it is being caught by a hood or pickup and carried off to a collector, it is under control. The trouble starts when it escapes: blown out of an enclosure, spilled at a transfer, or left behind by a pickup that has plugged. That escaped dust drifts and settles on floors, machine frames, beams and ledges, often far from the machine that made it.
So the form asks two different questions in each zone. First, is dust being caught where it is made? Second, how much has escaped and settled, on the floor and up high? A zone can look tidy at eye level and carry a heavy layer on the trusses overhead, which is why the high surfaces are their own question.
How much is too much
There is no single number every mill uses. A commonly cited rule of thumb is that a layer thick enough to hide the color of the surface underneath deserves attention, and that is the kind of plain-language description this form uses: clean, a light film, color hidden, a layer you could scoop, drifts. Your own dust program should set the trigger depth for each area and the cleanup it requires, and inspectors should apply that.
NFPA 652, the general combustible dust standard, and NFPA 664, written for wood processing and woodworking, describe how accumulations, dust collection, ignition control and housekeeping should be managed. In British Columbia, WorkSafeBC has published extensive guidance for sawmills after two serious mill explosions in 2012, and US mills may see the topic under OSHA's combustible dust emphasis program. This form records what you saw; it does not decide whether a mill complies with any of them.
Ignition sources and cleanup methods
Dust needs something to light it. In a mill that is usually a hot motor or bearing buried in dust, a slipping belt, a damaged electrical box, sparks from tramp metal in a chipper, or welding and cutting nearby. Each zone entry asks which of these you saw, so dust sitting on a hot surface shows up as a safety finding.
How the dust is cleaned matters as much as whether it is cleaned. Vacuuming removes it. Blowing it down with compressed air puts it back in the air as a cloud, which is exactly what an explosion needs, so when a mill allows blow-down the form asks which controls were in place: equipment stopped, ignition sources off, people cleared, collection running.
The plant-wide systems
After the zones, a few systems protect the whole mill: dust collectors, cyclones and the ducts feeding them, spark detection and suppression on the pneumatic lines, the written housekeeping program with its high-level cleaning cycle, hot work permits, and sealed electrical rooms. A collector that is down or a spark detection panel in fault changes the risk in every zone it serves, so they are checked on every inspection, not only at the annual audit.
Common questions
How often should a combustible dust inspection be done?
Many mills check their highest-risk zones every shift and walk the whole plant daily or weekly, with a deeper audit less often. The right frequency is the one that catches buildup before it reaches your trigger level, so zones that dust up quickly need checking more often. Inspect again after any upset, fire or near miss.
What is the difference between primary and secondary dust?
Primary dust is the dust at the machine, being made and, ideally, captured. Secondary or fugitive dust is dust that escaped and settled elsewhere. Secondary dust is the bigger explosion hazard, because a small first event can lift it into a much larger cloud.
Is compressed air ever allowed for cleaning wood dust?
Most programs treat it as a last resort, used only where vacuuming cannot reach and only with controls: equipment stopped, ignition sources off, the area cleared, collection running and upper surfaces vacuumed first. Follow your own program; this form records whether those controls were in place.
Does this form show we comply with NFPA 664 or WorkSafeBC requirements?
No. It records a walk: the conditions seen in each zone and the state of the plant-wide systems. Compliance with NFPA standards, WorkSafeBC regulations or OSHA requirements depends on your full program, your dust hazard analysis and the authority having jurisdiction.
Who should do the inspection?
Someone trained in your dust program who knows the mill: a supervisor, a safety coordinator or a trained crew member, ideally with the area's lead hand. A second set of eyes from another department often spots buildup the regular crew has stopped noticing.