How high is the risk of a dust collector fire from metal sparking?

[Dan Ness]

From reading different threads, it appears that there is a risk of a fire caused by metallic pieces (screws, nails, staples, etc.) being sucked into the dust collector when being used to sweep up the shop. From what I understand this is caused by sparking of the metal item when it hits the impeller (for single stage dust collectors). Since the impeller is right above a large bag of wood dust, even a small spark could start a devastating fire.

So my ? is. . .how high is this risk? Are there any documented cases of this happening? And if so, why are there dozens of companies out there selling floor vacuum attachments for DC without any warnings, etc.

When I first bought my single stage DC (soon to be upgraded to a cyclone), I also bought many attachments including the floor sweep wand, and the floor sweep gate, with the intentions of using it to clean up my shop floor, but ever since reading about this possibility, I have no longer use them.

So should I keep them in storage until I get a cyclone (if that is even safe?), or should I toss them and stick to my shop-vac/broom?

[glenn bradley]

I am sure the usefulness of a floor sweep is a matter of shop layout, DC power and any number of variables. I got rid of mine as I find that with good dust collection, the amount of "other" cleanup is so minimal that a broom and dustpan or the rare shop-vac-attack does the job. I also didn't have the floor space to spare to keep the path leading to it open ;-)

All that being said, I haven't seen any "official" studies or recommendations from the industry but, I have a home shop, not a pro shop and do not receive any professional trade magazines or other such. I do see "common sense" recommendations on the forums that any DC that passes the spoil through the blower should not be used for items other than chips and dust. Even the stray "chunk" of cutoff can ruin your day, let alone a bolt.

Let's hear from some of you that still use a floor sweep fixture ;-)

[Michael W. Clark]

If you are doing general floor cleanup, it is best to have a pre-separator before the fan. Cyclones are good at getting rid of metallic objects and sparks (burning particulate). From an industrial standpoint, DC fires happen more frequently than many realize. It is usually only documented, or makes the news, if there is a significant loss of property or someone gets injured. There are many instances where the system catches on fire, burns itself out or is extinquished, is repaired, then restarted. Cyclones are more forgiving (as long as the heat doesn't warp them) because there are no filters, internals, or electrical to replace.

How real is it in the home shop depends on how much metal you are picking up. The more you pick up, the higher the probability of having an event. I worry about pieces smoldering in the bag and catching on fire after I have left. I typically use a broom or shop vac for floor clean up since I do not have a pre-separator.

Mike

[Jamie Schmitz]

Can you put an rare earth magnet on or near the pickup attachment. I think static electricity is more of an issue.

[Dan Ness]

Well I was mainly concerned because every once in a while I would use the floor sweep and suck a screw or staple up into the system and hear the obvious clinging with the impeller. Then I started reading about the possibility of a fire starting. Especially a small spark that might ignite the fine powder/sawdust in a full bag. Didn't even think about the possibility of a hot chunk of wood getting in there.

Seems like more of a reason for me to get that cyclone/separator sooner rather than later.

[David Kumm]

I would not clean the crud off my garage floors after I went to cartridges. Dirt and sand are pretty tough on the fibers. Not applicable for those with a real shop. Dave

[Sam Stephens]

I would not clean the crud off my garage floors after I went to cartridges. Dirt and sand are pretty tough on the fibers. Not applicable for those with a real shop. Dave

yep. that's what a shopvac is for.

[Ben Hatcher]

Can you put an rare earth magnet on or near the pickup attachment. I think static electricity is more of an issue.

YES! We haven't had a good exploding duct work thread in a while. They're so much fun.

[Andy Pratt]

I'm in the camp that would rather deal with emptying the shop vac more often (and I run a hepa filter and bag in it all the time, you can re-use the bags if you are creative) than with all the floating dust created by sweeping. I feel like sweeping was a great way to clean up a shop floor until shop vacs were invented, then they became the best idea. If I had a smooth wood floor in the shop I might think differently but I'm on somewhat textured concrete right now and it takes way more effort to sweep than it does to collect it with the shop vac.

Only saying all this because I considered the floor sweep but didn't get it, and have never regretted it.

[Alan Schaffter]

Ok, here is the take, from someone who has had his cyclone-based DC connected in a "push-through" configuration for over 10 years without any issue. For those who don't know, a "push-through" is where the DC blower is upstream from the cyclone, so everything picked up by the DC hits my blower's 14" steel impeller before going to the cyclone.

Many know a little about me- I'm the guy who brought you the I-BOX, Lock Miter Master, etc.- so you know that I do a lot of tinkering and routinely work with both wood and metal. In over 10 years have I sucked up just about every kind of metal bits and pieces you can imagine- from nuts, bolts, metal cut-offs, to a drill press chuck key, and even a tape measure.

No fires, no near fires, no visible sparks, no smoke- NADA. I'm not going to say it can't or won't happen. I'm just giving you my experience and will let you make your own decision.

There are a number of reasons fire is less likely in a home DC system:

• Metal on metal contact doesn't always create sparks

• Air velocity in a DC is high and rapidly cools any sparks generated

• Sparks, if any, are too short lived to ignite the dust and chips.

• Air velocity reduces the concentration of dust in ductwork in home shops, further reducing the chance of ignition of the moving dust and chips. The conditions are very much different than high concentrations of slow moving or near stagnant dust in a grain elevator

• There is insufficient heat created for ignition and sustainment of fire

I'm sure you'll find reports of fires in commercial and industrial settings, but even they can be rare. There was a SMC thread in recent years that cited one example, but if you read the report you would see that the fire actually started at a machine, and burning embers were sucked up.

[David Kumm]

The one commercial fire I've seen involved cardboard rather than wood. Similar set ups are used. If it were a big issue there would be a mandate on impeller material. Both steel and AL are used extensively now. Dave

[bobby milam]

I remember reading an article recently but can't recall where. It addressed this and basically said that since there is always that possibility manufacturers have to address it for legal reasons but no documentation could be found of it actually happening in a home shop. I'm not to worried about it but my first thoughts were to attache a strong magnet across the intake

[Alan Schaffter]

I remember reading an article recently but can't recall where. It addressed this and basically said that since there is always that possibility manufacturers have to address it for legal reasons but no documentation could be found of it actually happening in a home shop. I'm not to worried about it but my first thoughts were to attache a strong magnet across the intake

At typical DC air velocities of over 4000 fpm (or 67 fps or 45 mph) you won't likely find a magnet strong enough to catch/stop much of anything, especially a chunk of metal with weight and considerable kinetic energy (1/2 MV²)!

[bobby milam]

At typical DC air velocities of over 4000 fpm (or 67 fps or 45 mph) you won't likely find a magnet strong enough to catch/stop much of anything, especially a chunk of metal with weight and considerable kinetic energy (1/2 MV²)!

Hadn't really thought about it that much but you are right.

[Craig Behnke]

At typical DC air velocities of over 4000 fpm (or 67 fps or 45 mph) you won't likely find a magnet strong enough to catch/stop much of anything, especially a chunk of metal with weight and considerable kinetic energy (1/2 MV²)!

i've played with some expensive rare earth magnets that are so darn strong it's unbelievable. they are nothing like the magnets you played with as a kid. I wonder if those are strong enough.