I’m in the process of building a workshop and have a wood burning stove that I will use for my primary heat source. It just occurred to me while I was planning out layout that I might have a hazard/ risk of explosion of dust particles. Does anyone have experience with this or advice? I plan to use dust collection, but how much residual risk of explosion is there? Do i need a spark in the room or would opening the door on my stove be enough to set the particles ablaze?
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Replies
In order for a dust explosion to occur, there would need to be a sufficient concentration of fuel (wood dust) mixed with the air. I don't have any data, but it would definitely be much, much more that you could tolerate.
Thanks for your thoughts on this. I didn’t give it much/ any thought and it sprang at me this afternoon and i got a bit of a panic. Interesting to hear the range of thinking on this.
BTW, this shop will be servicing a few of my woodworking related hobbies including furniture, cedar strip canoes and kayaks, and split cane fly rod building. Interested to hear more about your fly fishing. I’m currently vacationing in Mexico and determined to get my double haul working properly this trip. So far, i find i am thinking about fishing and not about casting!!!
I know an older gentleman (I think he’s in his early-mid 80s) who has had a wood stove in his shop for at least 40 years. He finally installed a dust collection system (moving WAY up from his couple of shop vacs) a few years ago. His dust collection prior to that was…sporadic? Occasional? Only modestly effective? I think all three phrases apply. (And he’s only moderately better now; I suspect his alveoli are lined with sawdust.)
Anyway, to get to the point: His wood stove burns from sometime in September to sometime in April, and if he hasn’t managed to blow himself up, I’d be shocked if you managed to. [Insert legal qualifier here stating that I am not a fire marshall, an expert in workplace fire safety, etc., and probably don’t know what the heck I’m talking about.]
Chris Beckvoort had one for a long time, but took it out a few years ago. No insurance company would cover him with a wood stove in the shop.
Personally, I wouldn't do it. Mini splits are great for heat and AC, and are cheap to run.
Oh2dovetail,
I don't know as I would worry too much about it. Other than insurance regulations/local fire codes, I think you'd be OK with it as long as you are careful. If you think about it, there must be thousands of folks who have the central HVAC furnaces sitting adjacent to the shop (mine was there for decades) with the pilot light happily burning away not far from all of that dust. Obviously, the newer systems don't have pilot lights, but some still do. And I imagine there are still hot H2O heaters with pilot lights in close proximity to the shops. After all, until other sources of heat distribution were invented, the wood stove/fireplace was the only source of heat in shops.
I could be wrong, it could be the most dangerous thing to do - I am no expert (insert a legal disclaimer here). Maybe shoot an email to Chris Beckvoort and ask his opinion on it? As John_C2 points out, there are other alternatives that may be better and cheaper over time than burning wood.
I wish I had one to burn scraps and botched projects.
I have two shops. A post steel building, started out at 600sqft. I had an old Ashley style wood stove in it and it worked beautifully. I doubled the size of the shop a few years later and sold the woodstove and "upgraded" to electric heater with thermostat. Big mistake. Wish I had the old stove back. I have a second workshop attached to my house about 12' X 23' I setup for turning ( 2 lathes). I have a small Vermont Castings wood stove in it and it works fine.
Install it properly, refrain from piling up flammable materials on and around it, duuh, just as you would do if it was in your home, and don't give it a second thought. Furthermore, you get to use your scraps for fuel. What could be better.
Short shop-scrap story... I do an annual camping trip, same group for 30 years or so...a kid I carried in a pail is an NYPD officer now. At the campground they sell firewood, but the woods are stripped of kindling. My shop scraps provide boatloads. It's also fun to answer what the various odd shapes were from. Things from those burn bags have been taken home by friends. Pretty cool.
One child became an Eagle Scout so we gave him fire starting duty. I brought a special bag of Ipe kindling for him. High-larious.
I don't think that a proper log burner with a sealed front is any greater hazard in the shop than it would be in the home.
There is a matter of needing to prevent stuff getting stacked against it, but otherwise it's fine. My log burner sits only 14" from two wooden pieces and they barely get warmer than the rest of the room.
There can be issues with home made burners, and with the burning of dust as opposed to solid scraps or pellets https://www.youtube.com/watch?v=kZSfvNZ06rs&t=205s but a commercial design should be fine.
Even so, an AC system is probably cheaper, especially when code compliance issues are factored in.
I heat with wood , always have, but not in my shop. I live in California now for many years so my heating requirements are not anything like they were when I lived in the Appalachian mountains where I did heat my shop with wood. Here in California I'm just trying to get a little chill out of the air or bumping up the heat a bit for glue to dry. I tried a Mr.Heat overhead propane heater but a by product of burning propane is water and I discovered that it raised the humidity in my shop to an unexceptable level so I installed an overhead electric heater.
In the early 70s I worked out of a shop that was in a pretty derelict old West Virginia farmhouse. I wasn't there when it happened but it burnt down. A new really nice shop was built to replace it. It was heated with a passive solar heat sink wall that kind of worked to keep it from freezing over night and a Vermont Castings stove that ran in the day. About 40 years later to my understanding that shop burned down as well. I had a cabin that I lived in in West Virginia. I heated with an Ashley Stove that went into a masonry flue. One night there was this incredible noise, like a 747 taking off. The stove was doing this huffing and puffing and I went outside to see what was happening and flames, like from a blast furnace, were shooting out of the chimney 20 feet high! The suction imploded the stove...like a crushed beer can! If I had just a metal flue pipe and not a masonry chimney I would have lost the whole house! Introducing live fire into a woodshop will creep out an insurance man for sure! With all of that said I still think it's reasonable to heat with wood,especially if your a woodworker, but you need to take special precautions given the nature of what goes on in a woodshop and what might be in there. A nice big hearth,brick or stone. Proper wall protection. A lot of thought and detail put into a chimney or flue. People like to cheap out there! A good stove is expensive but a good flue system can cost as much again or more. Fire extinguishers,and smoke detectors. Sparks and cinders find their way out of stoves sometimes and can create a fire hazard but I can't imagine what level of dust it would take to create an explosive mixture. It supposedly was a problem in old flour mills so I guess it could be possible. If your running machinery and have dust collection I d think it would be next to impossible for that to happen.
I was looking into heat for my shop a few years ago. Insurance agent said "no solid fuel source". Which eliminated wood, pellets, corn. He said if I did, insurance would not cover any resulting damage. I would check with your agent before you spend the money and find out the hard way.
I just re-filled my fireplace with scraps and got the fire going again from the hot ashes this morning, it’s -20 C outside so this will cut down on the heating bill. The fireplace is in the house but my shop is in the attached car garage so I bring in wood as needed. As a young kid we had a separate 20 X 20 garage where we had our tools and the only means of heating was a round vertical wood stove , it was barely enough to warm our frozen fingers but got rid of scrap wood.
Insurance companies and their idiosyncrasies often have undue influence, I believe. The same insurance agents that get antsy about wood stoves as heat go to the next house and sell a policy for a house with three open fireplaces. And then they go home and put the Noble fir they bought from the tree lot at the hardware store in the family room for six weeks during the holidays, six feet from their own fireplace, adorn it with electrical doodads, and let their heated and dry winter indoor air turn the thing into a heap of tinder.
I get that many folks just don’t any longer know how to properly manage and maintain a wood stove, or even a fireplace. But for those who do have the requisite knowledge, and wield it well, a wood stove is, I think, a wonderful thing.
But to each his/her/their/its/** own, I suppose.
Well said! I have been heating my 30' x 20' shop for over 5 years with a wood stove. It was professionally set up to all state, local and fed regulations; the entire chimney system cost me about the same as the stove itself. In rural Montana we heat our homes with wood as the primary heat source and a propane furnace as back up. In the shop, my back up is electric radiant heaters spaced throughout the shop to heat in the event the wood stove runs out of wood or I chose not to burn at that time of the year. Can't emphasize being clean, neat and orderly around a heat source of any kind, but especially wood.
I have a wood stove in my 30x40 shop, and use it occasionally without worry. My shop was designed to take care of itself as far as temperature; it is a passive solar, earth tempered building. Think walk-in basement with lots of south windows, without the house on top. North and west walls are buried 9' in the ground. Keep the chimney clean, as chimney fires are seriously bad, and keep flammables away from it. Otherwise, barring insurance problems, you should be good.
On the other hand, be careful how you make your dust collection system. There is where a spark can blow up/burn down your shop. If you use metal ductwork, make sure it is grounded in multiple spots. If you use plastic pipe (I did), run a BARE copper wire all along the outside of the pipe, attaching with sheet metal screws every few inches, to dissipate static electricity. Dust and plastic are a deadly combination. Ground the copper wire at every opportunity in case there is a failure at one grounding point. Metal ducting was much more difficult to find when I did my collection system over 30 years ago; I would probably use metal if I did it now. Just a bit safer if properly grounded.
Interesting comment regarding fire from dust system. Do you have any references or case studies? Thank,
Nothing I can send you to, except a vague recollection of a long ago article in FWW and maybe a follow-up letter or two to the editor.
I can say that when I first got my dust collection system running, I was crouched down in front of my table saw, feeding dust in its cabinet into the new system piped to its exit hole. It was kinda dark, and I started seeing orange flashes coming from the plastic pipe.Turned off the system immediately and started running ground wire.
Any industry that moves flammable dust (including flour mills) can have dust explosions. I live in rural Tennessee in a forested area, and there are lots of wood factories. I have been told by several friends in the local industry about factories burning down or being damaged by dust explosions. The metal ducting serves as a ground against static electricity buildup, but does not protect from pieces of steel being sucked up and generating sparks in the ductwork. There has been scientific research done on the density of dust required to sustain combustion or create an explosion. I just don't have a reference for it.
It is in practicable terms impossible to create the conditions that would result in the right fuel - air mix for an explosion in a home shop DC system. No such events have been recorded either, so if they occur, they are rare. It is almost (but not quite) impossible to achieve this in an industrial woodwork setting. The required amount of dust is simply too much, though explosions do occur in other industries where the dust is more combustible, more likely to propagate or produced in larger quantities.
It is also not possible to create a charge inside a hollow conductor such as a metal pipe, nor is it possible for charge to move significantly through an insulator, so the grounding of metal pipes to prevent static build up is unnecessary and grounding plastic pipes is foolish. Metal pipes should be earthed at several points, but this is in case they come in contact with live mains - it would be nice to be sure the breaker blows in such an event.
The main fire hazard posed by home shop dust collection systems is in the use of single stage systems where the impellers sit in the full stream of the collected dust. Metal fragments striking the blades may result in hot sparks which can cause dust collector fires.
Free dust in the shop is probably a higher risk than other issues - there have been catastrophic explosions caused by free dust in factories in the past, including two large ones in wood milling facilities.
The key though is the quantity being produced. Systems with multiple simultaneous users might possibly occasionally generate enough dust to create an explosion hazard, but that is simply not plausible in any home shop. Perhaps when cleaning up, if using a floor-sweep it might just be possible to reach hazard levels, but you still need the spark, and that is a risk that has nothing to do with earthing pipes.
In truth, the suggestion that PVC dust piping needs to be grounded is about as valuable as knocking on wood to stave off disaster.
https://www.woodcentral.com/articles/shop/articles_221.shtml discusses the physics of dust fires in great detail, and is written by an expert with appropriate qualifications.
As others said in earlier comments -- Best better to check with your insurance agent. Some will provide coverage, others will not. About 5 years ago I checked with several carriers about increasing my homeowner’s policy coverage and the coverage for my detached shop. Several asked if I had any type of wood/pellet burning stove or fireplace in the shop. If I did, they would decline coverage. Was told the same several years earlier when we first moved into the new house and shop.
Somebody's SEO guy is earning their pay...
For some reason, I have an ad for an "essential $75 cashmere sweater " at the top of this page. God knows why. I haven't owned, bought, or worn a sweater in 40 years.
I recommend you check with your insurance company. Many (most) will not provide insurance if your shop is heated with a wood stove.
A factor to consider is the suction created by a dust collector if you vent it outside. That could draw smoke down your chimney. So return the air back to the shop, which also saves the heat in the air.
I have a mini split in my shop. I’m very happy I went this way for a couple of reasons. First it’s cheap to operate. Second it takes up no floor space, which is a huge benefit. That lets me have more tools or materials in the shop, and also allows for improved layouts.
I burn the scraps in the wood stove in the house.
I'm just pricing out the mini-split option now. Put in a new heat pump in the house last summer and it may have enough capacity to also heat/cool the shop. Actually kinda excited about how much additional space this option could open up for me in this shop!!!
I have a mobile home propane furnace in my shop. Way in back away from table saw and any sanding operations. Yea, I get dust in the filters but there is no way I get anywhere near enough dust in the air to cause a explosion. As requested in an earlier post, I was looking for confirmed cases of dust explosions in a non industrial wood shop. Thanks
Looking at a couple of published case reports, these appear to occur when large amounts of very fine settled dust are dislodged from where it had collected. The first was thought to be a freak accident, then it happened again.
Most wood dust is too coarse to cause explosion, and shavings are never going to do so.
The settlings were fine enough to be suspended in the air and are of an ideal size to propagate an explosion.
Leaf blowers were designed for shop cleaning...
IMHO, every shop deserves a wood stove. In Portland, I have a mini split that keeps the shop above 50F. In the morning I get my coffee started and then fire up the stove to push off the night’s chill. By the time I come back out with my coffee, the stove has a good flame and the day is on.
I really like how the working areas of the shop can be comfortably cool, but I can sit by a warm stove during breaks or to take a call.
I harvest and mill my own lumber, so I have lots of fuel. I’d have a hard time getting rid of it without a stove.
Note that we are talking about wood stoves, not an open hearth fireplace, which would be crazy in a shop. I pay close attention when opening and closing the stove door and I keep the hearth below swept clean of dust and debris. I also sweep my chimney every couple of years, although I find that a modern, high efficiency stove produces very little creosote in the flue.
I too have had a wood stove in my 2-car garage-sized shop (otherwise unheated) for 30+ years, and have never felt worried about fire risk. One precaution I take that I have not seen mentioned here is that I have a 3-sided wire-mesh fireplace screen that I place so the back and sides of the stove are protected from something falling against the hot stove and resting there. It sits a few inches away from the fire-box of the stove. I think electrical stuff is more the risk in a shop.
Folks, for decades woodworkers warmed their shops with wood or coal stoves. ‘nuf said. Burn it every day ‘n burn it strong.
For decades -- centuries -- there were zero alternatives to wood or coal burning stoves for heat. You burned wood, coal, or you froze. And buildings burned down, frequently. Buildings were lost, people died. Often.
There are lots of alternatives now. Much, much better alternatives. Cleaner, more convenient, more and better heat, more even heat, more convenient heat. Totally risk free. And cheaper.
'nuf said.
Wood and coal burners do pollute. Not just outside (where it takes a lot of them in an area to create significant external pollution) but inside the room in which the stove is going. In fact, there seem to be recent reports that the internal gasses and teeny-weeny particulates are a real risk to the health of the occupants in wood burning abodes .......
It may be worth looking up recent studies of this indoor effect. I suspect that the degree of internal pollution will depend on the design and condition of the particular stove and what/how much it burns. For example, an older stove with leaky gaskets on the doors, burning damper wood, will be a naughty stove perhaps.
But add this pollution to the already extant risks associated with wood dust in the lungs and ..... the wood burner seems a poor mode for heating.
As John_C2 says, there are far better options. For an unheated garage attached to a house, I did two things: insulated the garage and set up a transfer-fan between the garage and the house, so that warm air from the house goes into the garage. This warm air is made with a ground source heat pump supplied with solar panel electricity.
A low speed fan not only warms the air but pushes it slowly through the garage, taking any airborne dust out with it. That does throw away some warm air to the outside but the trick is to arrange the fan's airflow to be slow but significant.
Insulating the garage or other workshop space means that the one kilowatt of heat a typical human body gives off when active will also knock up the air temperature by a few degrees .... eventually.
To John_C2 I recommend the cashmere ganzi too. One may buy them second hand for five quid on ebay, from fashion victims who may have worn them only once before becoming desperate for the next model. Add a merino baselayer with exciting wool tights underneath and heating in the 'shop becomes redundant except to make the glue go off. :-)
Lataxe, hot stuff.
I would think the homeowners insurance issues would be a deterrent. Not to mention the fact that you can't leave the wood stove unattended, or should wait for it to cool off before leaving the shop for the evening. Not to mention the possible effects of breathing the smoke.
I installed a Mr. Heater propane heater in my shop several years ago and find it heats well and little to no safety issues. I even turn the pilot light off if I am away from the house for several days for safety.
Wood stove owner in house, now have a pellet stove for ease of operation. The wood stove had a damper and air control to adjust temperature and burn rate.
If you load up a wood stove and allow it to come to equilibrium, there will be a lot of mass that is heated. There will be a lot of embers in the fire box that take a long time to burn out and cool. You could hasten this process by shoveling out anything in the fire box,
So if anyone thought you could just shut the stove down and wait for it to cool would have a l-o-o-o-g wait.
I am really confused by all of the danger with a wood stove in a wood shop. If you use current safety installation guidelines, I think 36" away from a wall for one, insulated pipe where required, no combustible materials by stove, I don't see why it would be any different that the one that sat in my house. The combustible dust concentration would have to be so high, breathing would be difficult. You must remember to clean out creosote from pipes.
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