MYTH BUSTED? Can woodworking dust REALLY explode? (And how to ground your duct work) 

Dr. Cole's Study: www.woodcentral.com/articles/s... Wire for grounding your ducts: amzn.to/2RG1Atg When you use this link to visit our sponsor, you support us► Clear Vue Cyclones (Use coupon code NUBS5): www.clearvuecyclones.com/ Subscribe (free) to Stumpy Nubs Woodworking Journal e-Magazine► www.stumpynubs.com/subscribe.html

Well done. I formerly worked in farm cooperatives. The GRAIN dust explosion threat is real. But grain dust is typically fine, like flour - which technically IS grain dust. GRAIN dust explosions typically happen when a bearing fails, gets hot, then something happens like the moving part falls, hitting the dust accumulation inside machinery. The first explosion is generally minor...but when the following GRAIN dust explosions happen, get out the popcorn and watch massive amounts of destruction. Each subsequent explosion kicks more GRAIN dust up in the air, and the flames from the previous explosion is the gift that keeps giving until there is either no more dust to agitate, or there is no more building to explode, which ever comes first.

Imagine, listening to a scientist. What a crazy idea. You're a rebel, James.

Nice. I like this. I used to work for a place that had a dust explosion, but it wasn't woodworking dust. It was ground corn and wheat, if you can believe that. Seems their QA department (who was in charge of cleaning as well as product quality) had let slip the filter servicing and the grinding room began to fill up with the fine milling dust. I never heard what they thought sparked the dust, but man when that went off (I was downstairs in the accounting department) it literally sounded like a bomb went off. Blew the entire side of the building off up there, which I'd discover it was designed to do. The room and equipment itself wasn't damaged all that much because the outer wall was designed to blow outward in such an event. I also learned that that is why no one was allowed to park, walk, or loiter on the grounds underneath the milling room. All that concrete falling from above would have been a nasty surprise. Never knew something like corn dust could even ignite!

Yep, I'm a retired Firefighter. Never went to a wood shop fire caused by Dust explosion. And I don't earth my dust collection in my own shop

As an electrician, only wood working "explosion" I have experienced were due to large amounts of dust building up in light fixtures

I’m loving your yakking videos. That injury is allowing you to pass along a lot of knowledge.

I'm an old retired firefighter (Scotland U.K) and I was trained in how to avoid dust explosions but that was for flour dust in mills not sawdust in woodworking shops although the principle would be the same. Various processes produce dust which in factories or workshops can accumulate on flat surfaces / beams etc. The theory was that if there was a fire in that facility, if we as firefighters hit the dust with a jet of water the dust could "plume" and plumes of dust (flour, wood custard ... almost anything) could burn explosively think big flammable dust mixed with air scenario. So we were trained to use water spray in dusty environments to avoid disturbing the dust. I can't see static igniting dust just laying around but if you have an ignition source - heater or "sparky" tool then a dust cloud could make life interesting..... or short. But you are absolutely correct in spotting a "friction" burn hitting your waste wood bucket. I love your work. honest simple stuff. Have you ever covered linseed oil n rags? Probably a more common problem than dust explosions

Yes, sawdust can and will ignite with explosive force if the conditions are right. However, your friend is correct about the math, and it is unlikely to occur in a home or garage shop. Another viewer said it hasn't happened commercially since the 1950's, but that's not right either. Sawdust explosions, while not common, do and have occurred in industrial settings recently. Fortunately, there are safety requirements which are supposed to reduce or eliminate this risk when follwed. From the volume of dust collection, the grounding requirements, and the restrictions on both particle size and count in the air, there are multiple federal and state regulations that, if followed, greatly reduce the chance of it occurring.

This should be a great episode for the Mythbusters

This is why I love stumpy, with the way he explains things, I feel so much more informed and as a result, more confident as a woodworker.

Great. Wasn't afraid of sucking up screws until now.

I'm not worried about my dust pipes exploding and showering me with sharp PVC; I'm worried about the dust in the bin smouldering for a few hours until I'm asleep and then catching fire and burning my house down. That's why it lives outside. When (if) I ever move the shop out of my garage and into it's own dedicated space, the dust bins will still live outside, but will also have a sprinkler system installed. The additional cost of adding sprinklers is tiny compared to the cost of building a shop and certainly a lot less hassle than rebuilding if the worst happens.

Another advantage to grounding the ducts is that it eliminates the dust and chips from sticking to the pipe walls because of static, thus sometimes causing blockages. I had this problem until I grounded my PVC system.

And who doesn’t like a good probing every now and then. 🤨😉🤣 I have had PVC duct work for years now, and I’ve never had an issue. Love your work by the way and I hope your hand is getting better.

Where I worked in Davenport, Ia. there was a huge grain elevator next door that experienced a dust explosion. It blew the 5 ton cap on the silo half way across the Mississippi, almost a half mile, even shut down barge traffic til the Corp of Engineers cleared it out of the river. A worker was on top of the mass, they found him 2 days later, alive!, but badly burnt. He lived, docs said his hearing will be impaired though. I was in my office at the time, my first thought was I was back in Viet Nam! Ever since then, I show the greatest respect for dust...

Great video James! Hope the hand is rehabbing well! My son has taken a real interest in your injury. He has been asking how I use safety in my shop. Everyone need a a good refresher on shop safety and not getting complacent.

Thanks James! I am rebuilding my dust collection system this week. This will save me the hassle of running ground wire. I ran it inside the duct last time which is a real effort. As an engineer I'm with the science. As the saying goes "There are people who are smarter than you. You should listen to them."

I have built a few dust collection setups for bigger CNC routers. They use galvanized spiral pipe that had to be connected to a grounding wire inside the flex hose. They were 7.5hp collectors so not too scary and never had any static problems messing with operators or equipment. There were a few problems where people hit screws on that held the spoilboard down and steel screws were sucked into the impeller but that never caused a fire. There were fires caused by tools slipping in the collet or too slow of a feedrate that would start welding the aluminum getting cut but these fires would travel into the vacuum workholding pump plumbing while not causing fires in the dust collection system directly above the smouldering MDF. It might have just been dumb luck but it seems like a properly sized collection system that doesn't have fine dust piling up in it is good enough for most applications.

Hello Stumpy, back in the 70's I worked in a large woodworking mill. It was called Michigan Maple and was located in Sault Ste. Marie Canada. We made butcher blocks, shuffleboards, solid maple tops, cutting boards etc. They had an industrial abrasive sander, and a finishing sander etc. I enjoyed your video. I have been a woodworker for years. The mill is now demolished unfortunately. Plastic has taken over unfortunately.

Great Info...thanks!

That is what I kind of thought, I know you use low voltage lights. We did have a local cabinet shop burn down from the accumulated dust in those large white commercial florescent light boxes. Just something to look for in all of our shops.

You are correct, and while it may appeared quite simplified, it is accurately described. The main problem I faced in my career in the fire service, both suppression, and arson/fire investigation. As it related to wood dust in the many woodworking commercial facilities in our county. Was housekeeping, fires could and would rapidly ignite and rapidly spread. Sometimes reaching flashover in mere minutes. Add in stain, lacquers, thinners and varnishes, well sometimes big booms would soon follow. A dirty shop is dangerous at many levels. Just one ex fireman, who often shook his head at avoidable conditions which threatened many others!

Great video. I hate people talking about things like this as if it was written in stone, yet when you ask them for proof they mock you or get all defensive.

Not with dust collectors but dumping a trash can full of table saw dust onto a construction fire (back in the day) created an explosion that blew the trash can 20 feet away and singed my eyebrows. That's why it was easy to convince me of the possible dangers. I have, however, dismissed most concerns as the years have gone by. Thanks your your research and quality presentations.

Very interesting and informative. I am planning on adding a dust collection system soon to my workshop. You gave me some things to think about. Thank you and stay safe.

Thanks for mentioning the random screw. I use a small portable Jet dust collector and one time made the mistake of vacuuming the floor. A screw or nail was sucked up and made a holy heck of a racket as it hit the impeller. The noise alone was enough for me to not do that again but also got me to thinking about the potential for a spark. Saw dust only.

Have to add my two cents in. I had dinner with a scientist who was an expert in explosives etc. He was investigating an explosion in a flour mill in town. Interestingly it was not the dust collector but the fact they had no means of removing dust that caused the explosion. Fine particles had settled over the years on horizontal surfaces and then the right spark and the right dust cloud caused the building to explode. So it can be said the danger is in the absence of dust collection not the process of dust collection. :)

That's a great idea to ground your dust collection system, I would ground mine if I had one, but not to stop some explosion, but to not get shocked, lol

Thank you, I came to the same conclusion because i have been around woodworking for more than 50 years.Taking reasonable precautions is a good idea but some guy just go overboard, me thinks it about click bait more than anything else. Theoretically Explosions can happen but like you, I have never heard of such a thing in a wood shop, even when I ran an industrial woodshop, I built custom doors and Trim to be used in commercial applications, my biggest concern was keeping the floors clean, not so much because of fire but so i would not slip and hurt myself. I use to know a man that was burnt over 80* of his body, He worked in a sugar processing plant in the state of Washington. you are right, the amount of fine dust required to create an explosion would have to be massive. There is more of a risk from fumes from oil based products in our shops than anything else. a friend of mine was replacing all of the counter tops in a house. He had applied rubber cement to all of the surfaces and He left for lunch, the heater click on and it ignited to fumes, it was probably not enough to do any real damage but it sure would have scared me to death if it had happened to me. proper ventilations is key.

The term you are looking for is 'finely divided combustible dust'. As you stated, there needs to be a huge amount of 'industrial' sanding going on to generate this type of dust. Saw, routers, planers and other chip producing devices do not produce this combustible dust. The building codes use the aforementioned term as a trigger for when sprinklers shall be installed in woodworking facilities. In a former life as a state fire marshal my staff encountered several instances where a group of people who did not use electricity lit their shops with gas mantles similar to those in old Coleman lanterns. My personal experiences with these shops was that they had a ton of sawdust on the floors but no 'finely divided combustible dust' in the air. I do not recall any dust -related fires in any of these wood shops. Actually, the only fires I can recall in a woodworking facility were from bearing failures in the dust collection systems.

While on the subject of dust collection myths, there is no need for the grounding screw to penetrate to the interior of the PVC. Simply providing a path of lessor resistance for the static charge to travel along will dissipate any buildup. My system has been in place for several years. It is grounded externally using simple aluminized foil tape running externally along the duct work and connected to a ground. Zero static build up, zero dust attraction. It doesn’t not take a high quality conductor to exceed the electrical carrying capacity of PVC so the static charge migrates to the foil tape readily and is safely discharged. I grounded my system to avoid annoying static discharges when in contact with the system and to prevent dust attraction to the charged tubing of an ungrounded system simply for cleanliness. Total cost, $2.65 for a roll of tape. The same principle applies to media blasting cabinets.

I think the random chisel sharpen on the belt sander is far more dangerous than any of these theories and I have seen very experienced wood workers sharpen on the timber belt sander. Thanks for the video.

I get static buildup on my sliding miter saw and during the winter I get shocked every once in awhile. No big deal. Very good video 👍👍👍

Watched the Ft Sill, OK fire department put out a fire in their woodshops outside metal dust collector. Took quite an amount of water to extinguish it as it was a smoldering fire with no flames. Fire fighters opened the chute and soaked it. I've seen similar fires in hay barns. There was no determination as to the cause.

Thanks. Always wondered. Was well aware of dust fires and explosions in grain elevators, coal mines, etc. Never really thought the problem was in the ducts, but in the air of a dust filled shop. However, your summary of the research paper, identifying dust density, airflow, etc as counter variables makes a great deal of sense. Good to know. Please keep it up.

Fire chief said her "She Shed" fire was not caused by dust collection.

My father worked in a sawmill in Maine. Had a dust explosion years ago. 1 killed, 1 severely injured.

If I had a nice system like yours I would ground it. Mainly because I HATE TO GET SHOCKED! James, thanks for the research on this! Years ago when I was brand new to woodworking, I was in the garage during the winter with a kerosene heater to keep warm by. I was making a train table from 3/4" MDF and using a shop vac for dust collection. After making most of the cuts I looked across the garage and all the air had a thick brown tint. Just like driving in fog. I quickly opened both garage doors and went out side to open the back door also. I will not say that MDF dust can burn or explode. I do not know. But having worked in the coal mining field for a few years and being required to take several safety classes, this scared the crap out of me! In the end, I replaced the shop vac filter with one rated for sheet-rock dust and I do not use a kerosene heater when creating a lot of dust. In fact I will use dust collect when ever possible. Black Lung; I've seen it. I assume the dust we create will do the same.

Based on your previous video about the ClearVue dust collector, I abandoned my previous system and installed the CV-1800. What a great system. I already had 6" duct work from all of my major pieces of equipment, so it was easy to install the new system. It's fascinating to watch the vortex. So far, the only strange thing is that the bin sensor goes off sometimes when I'm sanding with my wide-belt TimeSaver. Otherwise, it's a worthwhile purchase.

Thank you for yet another very useful video. I'm building a small cyclonic dust collector which I'll attach to a shop vac and I was worried. I've searched on line and I could find studies and regulations about the risk of explosion in dust cyclones but indeed, those were addressing mainly industrial cyclones used for grains and other flammable substances.

Being a bit of a safety nut, I attached ground wire to my PVC ducting, as Jim showed. I used sheetmetal screws. I also connected the bare copper wire to the large ground wire that connects the copper water pipes to a copper grounding rod that passes into the basement floor. I suppose the rod goes into the ground underneath the house. (I've read that that is not the best grounding scheme; The rebar in the concrete is better. Seems odd...)

In the early days when I used Shop Vacs on each machine and was doing piece work in basswood for Phoenix Millworks , no I didn't have an explosion but did get shocked by static sparks to make me think I had an explosion . But I live in the country and burned most of the scrap for heat or just to get rid of the excess in a barrel , word of warning in that case it will explode into a fireball big enough to set you on fire or at least burn off all your face hair , guess you don't need to ask how I know this . My wife saw it and said as soon as the dust hit the fire the fireball was 10 to 15 feet high and all of 10 to 15 feet around with me in the middle . Howed that happen you ask , the loos dust at the front of the shop vac can exploded in the barrel when dumped , blowing the rest of the dust into the air , and yes wood dust will explode maybe not in your dust collector but in a burning barrel yes it can so be VERY! careful emptying your Shop Vac dust we all have one so be safe if you burn it . God bless you all and don't be stupid like me .

The last comment about a screw hitting the impeller and causing a fire is absolutely on target. This is why I absolutely refuse to install floor sweeps in my system; the possibility of picking up a screw or similar is too much risk for me. That said, I'll always be proactive when it comes to static bonding. If you've ever filled an airplane with gas, you will always find a bonding wire (grounding is for electrical equipment, bonding is for static discharge). Airplanes generate a large amount of static charge when flying and it needs to be discharged before you get near it with metal and gas hoses. Good bonding is absolutely required when transferring fuel or flammable liquids, even though it is difficult to get them burning with static. There are numerous videos of gasoline hoses starting fires at gas stations due to people with nylon jackets or whatever, when people go to grab the nozzle. (Not cell phones, mind you). The other thing that can happen is oxidation. I worked in a machine shop when I was a kid. Clean up the metal shavings from the mill and lathes, put them in a steel bucket and take them out to the bin out back. My boss showed me why. Those shavings start to rust (oxidize) and, in the presence of oil, will actually catch themselves on fire just from that chemical reaction, if left long enough. That's also why workplace grease rag cans are metal, have lids and say "Empty every night". That said, wood dust isn't gasoline, or I'd run it in my Chevy. The main thing about fine dust and sparks is as you described; the ignitable ratio of air to dust has a very narrow range. Difficult, but not impossible. A small spark inside that space is very, very unlikely to start anything. Mine is bonded to a copper rod, because why not? My shop ain't going to burn down over that. Smoking, welding and grinding are banned and paint, solvents and gasoline are stored in a proper flam locker. I have insurance, but it won't cover my father's and his father's tools that I wish to continue using.

I think I tend to worry more about the old lumber mill style of explosion. Where you had a confined area and produced loads of fine saw dust that got air born. I always felt like a dust collection system mitigated the risk for explosion.

Agree 100%. I used to work at a plant as an electrician and we did have to ground a system similar to a dust collection system BUT like you said, we were moving very fine powder and alot of it. Just wont happen in a typical wood shop. Great simple explanation 👍

Thanks Stumpy, I had read soo much about making sure to ground all the ducts but then came a cross something that most articles seemed to miss. The pvc, or whatever plastic you use stays insulated inside and out due to the nature of plastic acting as an insulator. You would have to run bare wire inside the pipe as well. If explosions were that common in a home work shop, codes would require metal ducting to be used. Grounding the outside just eliminates the tiny shocks a person gets when touching the ducts.

Great video. I hope your hand is healing well. One consideration is if your duct air velocity is below about 4000 fpm, dust can fall out of suspension and settle in the duct. A small ignition can cause them to become suspended at the explosive concentration. Balancing the system is important and can be difficult. I agree with your conclusion, but correct design of duct size, cfm, and velocity are important. Thanks for the video.

The only static I ever get in my dust collection is the flex hose on my thickness planer. Trust me, I'm a freak of nature, in the winter if I even look at anything metal I get shocked. I even get shocked on the metal reinforced corners in the drywall when walking by. Maybe it's that 70's polyester wardrobe I wear? :) j/k

We used to use a candle and foot pump connected to a hose and put some dust or flour in a 44gallon drum with the candle in it stomp the pump and watch the barrel shoot sky high

You can see the hand injury he suffered back then. He inspired me to get a silicone ring to wear instead of my gold wedding ring.

if it does not save me from Bigfoot, I am not interested. Bigfoot is my only real concern. Which is why I never go into heavily wooded areas.

Hi James, I haven’t heard of woodworking dust exploding, but I have experienced spontaneous combustion! In fact I caused it. Off course there are a number of differences. In this particular incident I was kneeling on a rather large Oak boardroom table and sanding the top with a 4” belt sander, emptying the contents frequently into a plastic bucket with a plastic liner. The bucket got to be about 3/4 full and started smouldering behind me. I noticed a strong acryd smell and saw a fair bit of smoke coming off the bucket. I jumped immediately off the table, grabbed the bucket, ran with it outside and threw it off the balcony. By this time it was alight. I was very lucky, other than that terrible smell and a bit of smoke, nothing happened, except my wits suffered a heart attack. OK, there are a number of differences here, but this could still happen in a woodworking shop. First of all, there was no spark, only heat, 1/ from friction of the belt sander, 2/ the sanding dust contained organic material from the previous finish, 3/ the bucket itself and the plastic liner had thermal properties which helped with heat generation and running with it helped to add air. Oh, I forgot, as I passed through the kitchen on my way out, I put it under a tap, that made it worse. The owner of the property thanked me for my quick thinking and the job was completed successfully. There have been a number of these incidents in automotive and paint shops in particular with disastrous consequences, like buildings burning to the ground. So, could this happen in a dust collection system? Well yes, all depends on what’s being sucked up. The thing though is that a number of conditions have to be met, so fortunately spontaneous combustion is rare.

Thanks for an intelligent discussion of the issue of dust explosions.

Whoa! Ghosts in the shop! at 4:25 the water bottle moved on its own!

I spoke with a fire investigator once and his larger concern was cleaning the light switches and plug-in boxes. After I removed the covers I was amazed with the amount of fine dust. I now remove them and blow out the boxes twice a year, but then I have been called a neat freak.

On a little Larger Scale, I live near and have worked at Sauder Woodworking and they have had several dust explosions throughout the years.. I am also a retired fire investigator and yes given the right combination of factors it is possible to have this occur in a home shop. ***** Likely No.... Possible ( right combination of factors)...Yes

Excellent, as always. The idea that dust INSIDE the pipes/hoses will spark and explode is nonsense. Free flowing dust creates static ON THE PIPE (like a capacitor) and only when being suddenly grounded (like when you touch it) will there be an arc ... OUTSIDE the pipes/hoses. I did ground mine but not for safety reasons. The only reason I did it was because at times dust will stick to the outside of the pipe (think styrofoam or acrylic plastic) which was very annoying. Thanks Stumpy! BTW, I haven't checked the vlog but will after I commit this comment, I hope your hand is doing well. :)

I have gotten some wicked shocks off of dust collector hose. The worst ones have been during the dead of winter when is bone dry and when I was using the planer with its own isolated dust collection. I now have an independent ground wire/plug for it now.

I buy Victorian (19th century ) oak furniture at auction, and use it in my workshop. A real shame to break up nice furniture, but nobody wants 'the brown stuff' here in the U.K, and it is lovely wood. As it has had over a hundred year's of polish the dust from that is truly explosive, even the coarser stuff from my planer vac. I once (stupidly) threw a bag on a bonfire and it blew it 10 metres apart, and singed my beard! Like you, I can't see wood dust ever being fine enough, or thick enough in the air to explode.. I do know flour mills were built with all wooden gearing etc, to reduce spark risk, and some of them even had roofs that were designed to blow off easily in the event of an explosion, to save the walls. I used to live near Byant & May's match factory (even higher risk), and that was the same, and had had three roofs replaced in over a hundred year's production.

I totally understand the concept of needing sander dust and large amounts of it. I worked at a plywood mill where an Industrial plywood sheet sander picked up a nail. It caused some major sparks. The sparks continued through the duct system hit the 5 story dust storage tank. It blew the top off the tank. The only thing that saved the tank and surrounding buildings was the fact that the tank was over 3/4 full. The sprinkler system was functional and soaked the sander dust in the tank. I and a few other guys spent the next two days digging out the wet saw dust until we could get the augurs to turn. This was not your 250 CFM small shop dust collector.

Love your work James, learnt so much. The first thing I look for is the strapping on your finger, I then know it’s a recently updated vid. Take care mate

I worked in a large shop with a bunch of inexperienced people who could be pretty careless at times. We had one of those industrial nedderman units with a 12" inlet pipe. Guys would cut thru nails left in pallet boards and send sparks up the hoses of the miters saws i guess because moving the board over 1/4" was too difficult. One time one such nail went up as well and succeeded to catch the dust on fire on the collection bag. Saw dust just smolders without bursting into flame. Then it seems to repel water dumped on it. They put it out as far as they knew and threw the bag in the dumpster, and two weeks later there was still smoke coming out of it. So yeah, no explosions. Just slow ubiquitous smoldering. We sucked up bits of nails off the floor all the time as never had any trouble with them sparking when hitting the impeller. I did meet a guy at home Depot who said his friend had his dust collector bin catch on fire from the static, but that wasn't an explosion, and still hearsay.

The immense relief I felt for no longer having to worry about my dust collector exploding was quickly shaken away when I now realize I need to update my dust bucket to metal...

Stumpy, Sorry about your hand again! As an electrical engineer that has done electrical designs of several Hazardous Areas classified as explosion proof area, I 100% agree with your statement of no way to cause an explosion. Myth Busters showed coffee creamer exploding and I have seen RU-vid videos using very fine saw dust. The reported danger would only be in the shop, not inside the duct. Trust me, that you would have to have air in a tank feeding a mask in order to have that much dust in the air to be at the correct amount to be explosive. Otherwise you could not breathe at all. Respectfully, Kevin

"What's yours made of?" Da, Da, Daaaaaaa! lol! Nice one Stumpy! :)

I was a member of a small VFD for 13 years. We did have a a fire that sawdust did contribute to the fire . It was not caused by static electricity, it was started by someone lighting a cigarette in said shop. A lathe machine had been used for a large project and had been running for nearly an hour non-stop The sawdust in the air did ignite fr the gentleman lighting his smoke.

Good analysis and suggestions. Folks who have wood stoves know how difficult it is to get wood to burn, when you want it too. I just finished a construction project that generated a lot of wood dust from a plainer, saw table and sanding. Different size chips... the plainer was like shavings and the sander with 220 paper was fine dust. I saved it to see how dangerous it was by testing a little in my wood stove. I wanted to know my risk of fire. You would think a handful of wood dust would explode when tossed onto coals that are at 400+ degrees. It didn't! In fact if I added it too fast the fire would start smoldering and put out the flame?!? If I tossed a match onto a pile of saw dust the match would go out due to what I call a humidity cloud. What I noticed with wood fires is ... because water does not burn, during the early ignition phase there must be enough heat energy to evaporate the moisture in the wood until it is ready to toast and burn. This is why some fires go out if you add wet wood or add dry wood too fast. The chamber is filled with humidity and changes the equation for fire.

Boy, this topic can sure spark a conversation! 🤣🤣🤣

One thing to note - if you use a CNC router to add repeatable carving, etc. to your various builds, then grounding your dust collector is pretty much a required effort, especially if you maintain your shop as a low humidity area so that your tools do not rust as easily and your wood supplies dry more quickly. If you do not, then you take a very likely chance to have your controller drop out of your job somewhere in the middle of your CNC project run. I had that problem during winter months shere in Maine until I grounded my dust collector piping all of the way from each tool on the system back to the collector's ground screw. I have not had the controller drop a run in the middle of a project since doing that.

Oh Stumpy...you and your facts and data! Thanks!

Well done! I've had a few people over the years tell me about the dangers of sawdust and it always seemed silly. It's not a mill grinding grain and making air float sized particles. I'd be more scared if sawdust or rags combusting from oil than I ever would dust floating in the air (and we all know the danger of an oil soaked rag.)

25 years as a 911 Fire/EMS dispatcher never had a sawdust explosion. We did go to a door manufacturing plant several times for fires in the duct system and the worst one was in the collection bin outside the building. Poorly installed and maintained duct work was the culprit there. So I wouldn’t worry about an explosion but a fire is a possibility if your system is improperly installed and maintained.

Here where I live are a lot of kitchen and furniture producers. They tend to have "dustbins" and vacs the size you in the US might know from corn silos in the midwest. As you said right the greatest threat for them is hitting some metal (even in particle board there is a lot) if such a spark ignites inside the silo the fire department can erect a camp side next to it get the fire out. A friend of mine is a volunteer fire fighter and he told me that they regularly get trained on what to do if these things start smoking. Cause thats what they do they will smolder for days and due to the collapsing danger no one will go near or inside until its flooded from the roof. This happens once or twice a year (yes news paper articles available in german ;-) ). Another person I know is even working on sensors with radar and xray that detect these spark inducing things in the ductwork to eject them before they reach the silo that is now a requirement to build new factories to code and get a permit here in germany. Dust explosions can happen in smaller carpentries when an event like a puff from solvents ignition shakes the roof stringers which in turn shake of the accumulated dust causing the puff to get really big.

I used electric fence wire. You can buy a quarter mile of it for around 20 bucks. You will be amazed how useful it is around the shop and house, and because it is galvanized, it won't rust outside for years. I use it for hanging all kinds of things, like when I'm finishing projects, just hang the piece, and you can apply your finish on all sides at once. I even use it to wrap around the ends of small stacks of lumber to keep it from warping and twisting in storage, just give it 5 or 6 wraps on each end. A roll will last you a very long time. Check Tractor Supply, or Fleet Farm.

Perfect timing. I was gonna buy some wire tomorrow. Thank you.

Thanks for the information James, sets the mind at ease some about this problem. You got my attention about the plastic construction of my dust can collector. I’ll be changing to metal cans!!

I've been a millwright for 20 years. The danger is dry dust. 12% is average and damp. And mills over the years cut costs on clean up. Williams Lake was huge it leveled the mill. It's never happening in a home shop. The dust explosion is dry dust that sits on top of the pipes. Once it ignites it's explosion is sucked through the building.

What I do for static control is to mix fine graphite into some paint to make it somewhat conductive, paint the object in question, and then ground that. I do that not just for dust collection; but anywhere I want to keep ESD under control (for example, I have a DIY pick-and-place machine for doing electronics assembly, and the 3D printed parts are all painted like that so I don’t fry any microchips).

Great info on the dust collector "bomb" issue. Thanks for sharing!

Perfect timing, I'm building a CNC in my garage which has a Reznor gas heater and was wondering about this exact question. Of course I'll be sure to blow off the heater it's self to avoid dist build up on it.

On the note of industrial etc, the stuff that falls under hazardous locations or intrinsically safe often just referred to as explosion proof for the reason of dust is intense to work around. I don't believe there is a risk of explosion in anyone's garage like James mentioned, but something to consider in the case of static ignition is a fire. I had an issue while using a router with a dull bit basically burning through the wood. Actually created enough of a smoldering ember that was sucked up. It never got to the point of a big fire cause I smelt it and saw the smoke coming from my extractor and quickly acted. None the less could've been a serious issue had a left the garage like that. Lesson learned not to do that again, but I believe the static could cause a fire the same way in rare cases where the stars align and the moon and Sun are aligned and James is having a beer, which simply can be avoided by grounding your system

Great video, as someone who does alot of welding and fab in my workshop I'm much more worried about something smoldering than exploding like you mentioned at the end.

The high impedance of PVC does make it a candidate for making static electricity and holding it, waiting for you to come along and touch it and feel that tiny jolt of static electricity. IF that bothers you, you can defeat it by spraying your PVC with ordinary dish soap. That will leave a coating that is a conductor and prevent static electricity from building up on the PVC.

Judging from the number and variety of comments, I'd say you have opened an un-grounded PVC can of flammable static worms. And Bigfoot. Well done sir!

Ground my duck?! But he loves to fly! J/k - loved this vid!

Great videos. Dumb question I am a new woodworker and was looking at a 1.5hp wall mount Grizzly. I have a small basement shop and was planning to use flexible hoses. Do I need to ground that too or is it just pvc piping ? Thank you so much

Great info as always James!

I would worry more about that can of lawnmower gas setting or there by the propane bottle! I think the duct should be grounded just to keep from getting zapped by static electricity.

James, great explanation. I hope the hand is healing quickly

The title made me think of the episode of MythBusters where they ignited a giant cloud of coffee creamer.

I had great trouble getting home insurance because of this exploding dust nonsense (the workshop can't be in the garden, sadly). After shopping around a lot, I managed to find one that would cover us, provided I had a properly certified extinguisher in the workshop. It turns out a lot of those with a small home workshop aren't insured, at least in the UK, even if they think they are, & that it's far harder to get insurers to see sense when it comes to sawdust than flour.

I had a pacemaker installed about 2 years ago, and it records all electrical activity for a 3 month period before reporting (yeah, it uses Bluetooth to connect and report data to a base unit by my nightstand every night around 4am, that my Dr can read over the internet), and was sanding fiberglass with a shopvac attached to the sander. Yeah, I got zapped by the static electricity lol. Doc saw that and freaked out on me. "What the helll are you doing?!" A little speaker wire solved the issue... so far.

I decided it was easier to concede that I un-necessarily grounded my ducts than to take the abuse of the know-it-alls who just can't let the argument go.

Given the right ratio of air to dust an explosion is possible. Grain elevators are a prime example of dust explosions. Powdered coffee creamer trickled over a flame appears to flash, it’s more the oxygen that’s burning just like steel-wool and a spark. It has to have the ratio to work. Far more likely to have an explosion from a lpg tank leaking or getting bumped on accidentally. Doesn’t take a large tank of propane to blow a house apart.

i never grounded my pvc duct work after reading that unless your running it flat out constantly as in a manufacturing environment you would never create anything that is likely to combust. and of course manufacturing setups are a lot bigger and generally use metal ducting so no problem. as i only use one machine at a time and the collection is turned off afterwards i believe i have absolutely no chance of a fire.

I got the worst shock of my life from one of those tiny cyclones attached to a 5 gallon bucket. I dumped the bucket out and then reached in to clear a bit more debris and got a huge zap. I've been shocked with 120VAC a few times and this was definitely worse. If I ever get around to building a proper dust collection system for my shop I'll be using the metal pipes for dryer exhaust.

You may be correct in the circumstances you are describing BUT!!! I lived on a boat in Wilmington, Ca (LA Harbor) and a guy died while sanding the inside of his boat. They determined that the dust collected and a spark (possibly a cigarette being lit) instantly infinited and the entire boat blew up. It was so tragic and a very sad day for all of us.

I wanted to put my earthing wire on the outside of the ducting but when I asked the extraction system manufacturer they insisted it needs to be on the inside. Part of what I machine is nylon plastic which comes off in sometimes 20mm long circles and tends to clump together. If I try to suck that up the hose in clean up it gets stuck round the earth wire so it ends up quicker to bag the clumps of it by hand. It would not take too much convincing to redo it like yours.

Heard many times about this issue and was not sure if I have to worry about it. I heard that building ducts from metal pipes eliminates this problem totally, so I’ll do my duct, which is not that long, from metal pipes. Thank you for explanation.