# Woodstoves and Flash Explosions



## TZH (Oct 20, 2009)

In doing a bit of research on this, I was able to verify what I already knew about dust and/or sawdust causing flash explosions if sparked. What I haven't been able to find anything on is whether woodstoves are a risk, big or small, for flash explosions.

I try really hard to keep my shop as dust free as possible even though I don't have a conventional dust collection system. I use a leaf blower to get rid of sawdust by blowing it out an open door (gotta open and close it this time of year where I live) even during the work engaged in.

The issue is I have one of those jet heaters I've been using after having moved my shop from a heated building over to another building on our property that isn't heated. The jet heater can't keep up with the cold weather and I'm really anxious using it while creating sawdust doing what I do because it's basically an open flame being thrown into the work space. Here's a photo of the type of heater I'm talking about.










In any other environment, this heater has been more than effective for me. In a woodshop, the unknowns are a bit scary. So, we've decided to sell it and are considering putting in a woodstove. And that's where this post is leading….to a question for all you more experienced LJ'ers as to whether a woodstove might be the way to go? I have no doubt it would heat up the shop and keep it warm enough while I'm working. The question is whether or not I run the risk of blowing myself up while doing it…...HELP!!!!!

Thanks for your feedback, suggestions, and recommendations.


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## TiggerWood (Jan 1, 2014)

I thought about putting a wood stove in the opposite corner of my garage but it just seems like the most dangerous way to heat a wood shop. I think it would be more likely to start a fire than your jet heater.


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## cabmaker (Sep 16, 2010)

the jet heater as you call it…...i have been using for approx 30 yrs with out incident. I have never burned anything other than diesel in them.


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## TZH (Oct 20, 2009)

Thanks, guys. One thing I forgot to mention, too, is with regard to economics. Because my shop is not insulated, it seems the jet heater (not sure what the actual name is….I've seen turbo jet and portable, but would be interested in other names, as well) goes through an awful lot of kerosene fuel. During one cold snap, I went through five gallons in a matter of a couple of days, and the shop never really got all that warm.

Anyway, I also found a website forum (http://forums.finehomebuilding.com/breaktime/general-discussion/wood-stove-wood-shop) that kind of shows the wide range of opinions on this. I do appreciate you guys weighing in on it.

TZH


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## pjones46 (Mar 1, 2011)

I would not use the jet /torpedo heater due to Carbon Monoxide output in a closed space coupled with ambient dust explosion likelihood.

That being said, I have/do use a airtight wood stove for over five years without any incident but keep the shop vey clean. It is a great way to get rid of small cutoffs and scrape wood that would otherwise have to be thrown out at an extra cost and gives the benefit of heat.

Of course my shop is insulated very well and that in itself helps to keep the heat in. My shop is 24' x 36' with 10' high ceiling all of which are insulated.

I also had to deal with cord wood to heat which was a pain as I got older, so, this year I put in a Propane way oversized 135K BTU airtight ceiling hung Modine Effinity 93 heater and have been very happy with it so far, but was not cheap to get and install.


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## EMWW (Nov 25, 2015)

I think that a woodstove would be fine. That is what I heat my shop with. A few things to cation you with are do not cut cost on the instillation and make sure it is as good as it can be. I learned this the hard way from seeing fires caused by poor installation. Also make sure you plan at least an hour on warm-up time depending on the size and insulation in your shop. I usually use that hour to clean up and to prepare stock. I hope this helps.


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## TZH (Oct 20, 2009)

More very good information…..thanks.

The carbon monoxide thing isn't something I'd even thought about!

Hoping others are learning as this discussion goes along. I know I am!


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## conifur (Apr 1, 2015)

I worked for 20 years in a coal fired Power Plant, we pulverized the coal finer then talcum powder, it gets blown into the boiler section, it flash burns in there, we never had an incident at any of the 5 PP that are utility ran. I was at a safety demonstration at a old PP that was going to be destroyed/razed, they did a coal dust explosion in the facility, cameras ect, fuel air monitors, ect, for the air to fuel mix to achieve it the air had to be almost impossible to see through before they could get it to the right mix to flash explode, and they had propane torches burning as igniters.


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## JoeinGa (Nov 26, 2012)

I used to use one of these torpedo heaters in my shop. I always blew it out with compressed air before firing it up in the morning and then when I'd break for lunch I'd blow it out again. Never had even a hint of a problem that way.

Now I have this on a mobile stand that I welded up, rather than mount it at the ceiling. and I just move it to the area I'm working in. Works good.
.
.


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## AandCstyle (Mar 21, 2012)

TZH, I have always called them salamander heaters. You should be okay with an air tight wood stove, but do NOT toss saw dust into one when it is burning, because the dust can be explosive. Also, check with your insurance agent before buying one. Another option would be to buy a wood furnace which is a wood stove that sits outside your building and the heated air is blown to your building via an under ground duct. However, I would insulate your shop before doing anything else otherwise, you are just burning dollars and contributing to global climate change.


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## patcollins (Jul 22, 2010)

Have you thought about something like this, it warms what it is pointed at but not the air.

http://www.amazon.com/Optimus-H-4438-14-Inch-Energy-Saving-Oscillating/dp/B001F5ST84


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## JerryLH (Oct 23, 2014)

I took a furniture making class in Pennsylvania (I'm from Oklahoma) and the school's owner used a wood stove and always has. Many people working at one time, lots of dust - no explosion. The school is - JD Lohr School of Woodworking. I'm sure he would be glad to speak with you. http://www.jdlohrschoolofwoodworking.com/


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## RogerM (Oct 31, 2011)

I have an extensive insulated shop and have used a wood stove (LOPI) for over ten years with no fire or combustion issues whatsoever. Love a wood stove in the shop and would do it again if I were building another shop.


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## shipwright (Sep 27, 2010)

I have used wood stoves in my various shops for about twenty-five years and think they are a great solution to all sorts of problems…. Cold shop, buildup of scrap wood, and yes, a great place to burn your sawdust and chips. I regularly add a half shovelful or so of sawdust, even fine floor sweepings into the burning fire with no ill effects. If there is a lot of fine dust in it and you are too vigorous in your tossing, you may get a little very localized "woof" at the door of the stove but that is the extent of the "explosion".


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## bbasiaga (Dec 8, 2012)

In order for dust to flash, it has to be small, dry enough, and create a dense enough cloud. Basically, the cloud must be thick enough that you can't see your hand at the end of your arm. This, of course, can happen in an area the size of a dime, which explodes and lifts more dust, which then also explodes…etc.

So any source of heat or spark that is in close proximity to dust is a risk. How much of a risk? That depends on how old and how dry your dust is. A clean shop is a safe shop. Fresh dust that hasn't had a chance to dry is less of a risk than old dust that sat there and dried out. A wood stove is less of a risk because it doesn't circulate the air. However, if dust is allowed to settle on it and get bone dry, then a cool breeze and a static discharge at the wrong time could be a problem.

I spent several years engineering dust explosion prevention systems. I wouldn't call myself and expert, but I would say I am pretty well informed. A lot of wood working businesses that have had dust problems have them in the ventilation system, where dust collects, dries, and static builds up. Fires (vs. dust explosions) happen when sparks or slag is sucked up into the dust collection or ventilation system. Don't do metal work in your wood shop.

I can't say your home shop is not an explosion risk. But I would say, as mentioned above, your jet heater is a way bigger risk for carbon monoxide poisoning than dust explosion. Switch to something that doesn't have an open flame, or is vented outside like your furnace.

-Brian


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## conifur (Apr 1, 2015)

I worked for 20 years in a coal fired Power Plant, we pulverized the coal finer then talcum powder, it gets blown into the boiler section, it flash burns in there, we never had an incident at any of the 5 PP that are utility ran. I was at a safety demonstration at a old PP that was going to be destroyed/razed, they did a coal dust explosion in the facility, cameras ect, fuel air monitors, ect, for the air to fuel mix to achieve it the air had to be almost impossible to see through before they could get it to the right mix to flash explode, and they had propane torches burning as igniters.
THATS WHAT I SAID!!!!!!!!!!!
In order for dust to flash, it has to be small, dry enough, and create a dense enough cloud. Basically, the cloud must be thick enough that you can't see your hand at the end of your arm. This, of course, can happen in an area the size of a dime, which explodes and lifts more dust, which then also explodes…etc.

So any source of heat or spark that is in close proximity to dust is a risk. How much of a risk? That depends on how old and how dry your dust is. A clean shop is a safe shop. Fresh dust that hasn't had a chance to dry is less of a risk than old dust that sat there and dried out. A wood stove is less of a risk because it doesn't circulate the air. However, if dust is allowed to settle on it and get bone dry, then a cool breeze and a static discharge at the wrong time could be a problem.

I spent several years engineering dust explosion prevention systems. I wouldn't call myself and expert, but I would say I am pretty well informed. A lot of wood working businesses that have had dust problems have them in the ventilation system, where dust collects, dries, and static builds up. Fires (vs. dust explosions) happen when sparks or slag is sucked up into the dust collection or ventilation system. Don't do metal work in your wood shop.

I can't say your home shop is not an explosion risk. But I would say, as mentioned above, your jet heater is a way bigger risk for carbon monoxide poisoning than dust explosion. Switch to something that doesn't have an open flame, or is vented outside like your furnace.

-Brian


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## bigblockyeti (Sep 9, 2013)

I wouldn't worry about it.


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## DocSavage45 (Aug 14, 2010)

I have a kerosene torpedo heater. Unless you have a lot of air leaks there might be an issue of carbon dioxide. My friend has the garage ceiling heater and it worked well except when I was working in his shop I was having burning eyes from the fine dust hitting the burners. He didn't bellieve me , until his grand kids had the same reaction.

Depends on what you use your shop for? I have a dust filtration unit by Grizzly. I also installed a forced air gas furnace with ductwork for the four zones in my little barn workshop.

I can work out there in 10 degree below weather although the furnace has to run too much.

Thought about a well made wood burning stove like Paul has but my insurance company won't cover it.

Good luck


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## wapakfred (Jul 29, 2011)

As Art said, another name for those is a "salamander" and that's about the only thing I've heard them called. Also as someone mentioned, worrying about a dust explosion with a wood stove is wasted worry. I had one for 6 years in my last shop and used it as the main heat….the only reason I took it out was to free up floor space for an assembly table. I love a wood stove for heat, there's something magic about a crackling fire while you're working wood. But also as mentioned somewhere in here, make sure the installation is properly done.


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## Tennessee (Jul 8, 2011)

I'm not much of a fan of the salamander heaters due to the fair amount of fuel they use, and the constant noise of the fan.
I ran a woodstove, a double 55 gallon barrel unit in my 28' by 28' woodshop back when I lived in the Poconos. My only complaint was it took a while to get that space heated up since I let the fire die when I left the shop for the evening. But I never had any flashing problems, and we used to throw our sweepings into it and burnt everything from slab wood to scrap pieces to pallets. We even sprayed poly with it running, and while we were still masked up, we'd look into the air opening and the flame would be purple!

Now that I have a much, much smaller shop, with lower ceilings, I use a standard kerosene heater with two of those Grizzly filter box fans in the ceiling. Works great, and there is enough gaps in the garage door that it all works well. Oh, and I also live in SE Tennessee now, so my heat needs are much, much less.


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## bigblockyeti (Sep 9, 2013)

Joe, how much power does that electric heater draw? I'm guessing it's 240V?


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## mojapitt (Dec 31, 2011)

I use the jet heaters. Have not had any issues.


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## distrbd (Sep 14, 2011)

There are two huge problem that the "forced air propane heaters " create:

#1= is the amount of Carbon monoxide that if you are not watching could easily be fatal.but in an enclosed (Small)garage 10 minutes or so is plenty,if any longer period is required , opening of a widow just a couple of inches could do the trick.

#2= is the amount of moisture these heaters create,the fist time I ran my heater for 20 minutes with all the doors/windows closed, I noticed small pools of water on cold surfaces and I first though we had a roof leak.that moisture is an inevitable part of these type of heaters though and again can easily be remedied.

I do use my forced air propane heater but 10to 15 minutes at a time,the rest of the time I use Radiant heaters ,got 2 of them, both burn electricity but they quickly heat up whatever is in front of them which is me and the work bench.


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## 000 (Dec 9, 2015)

Space heater here. 
I've never heard of a *small shop* blowing up from a dust explosion. Not saying it can't or doesn't happen but I don't know of any stories about it happening. I think the dust to oxygen levels have to be just right in other words there has to be perfect conditions, which are very very hard to get, for it to happen. 
Here is a good article 
Mostly talks about sparks inside a pvc dust collector, but it also talks about conditions needed to create explosions..or not!


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## eflanders (May 2, 2013)

I've had 4 different types of heat in my shops over the years and I live in far NE WI. My least favorites were the kerosene and diesel powered units. They stink, use a lot of oxygen and the heat is very inconsistent throughout the shop. Radiant floor heat is the most comfortable, but hard to retrofit. Forced air units spread dust. Overhead radiant heat is high in initial cost and sometimes long-term depending upon it's fuel source. Hydronic heat is as good as radiant floor. I know guys that use solar and fuel fired radiators that love their system. Stoves are easy to find, fuel and retrofit. But insurance companies hate them! Anything with ignition (flame), insurance companies will be very critical of in a woodshop. They tried to drop me for having a LP heater once and then another time for a wood pellet stove.

Electric is safe but very costly as compared to most others. Fuel oils stink and can be costly. The same is true for gas fired units. Wood is the least costly IF you harvest your own.

IF I ever build another shop, it will have radiant floor heat fueled by mostly solar and then use wood as the backup. The firebox would be located outdoors for insurance reasons. This would allow me to burn scraps safely and get heat from it.


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## TZH (Oct 20, 2009)

WOW! You folks are amazing! Some very, very, very good info to cogitate on.

Just one of the many reasons I love this website. Ask a question, and it will be answered!

TZH


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## distrbd (Sep 14, 2011)

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## ClammyBallz (Apr 16, 2015)

My old shop, when I was a kid, had a pot belly stove and no dust collection. I never had an issue or concern with the stove in there. I used a torpedo heater running diesel to heat up the shop while the pot belly was heating up. I kept the door cracked to let fresh air in. If I was making dust, I'd shut down the torpedo heater because I could see the dust firing up through the heater.

When I moved to my 2 car garage, I had a 30K BTU propane heater which kept it warm all the time, but all the walls and ceiling were insulated. There was condensation on the windows because it wasn't a vented unit, and sometimes the windows would ice up. If I was sanding, I would shut down the heater, I could see the flames turn orange when there was dust in the air.

My current shop is 2000 sq ft in a 4000sq ft building (part of it is rented out for storage). It's on the second floor and the 1st floor is heated, which keeps the floor warm. This is my first year running the shop in there and the coldest it gets is 55F without the heater on. I picked up a 5kw electric heater from HD and mounted it on the ceiling. The heater bumps it up about 2-3 degrees in an hour, enough to take the chill off. If I let it run for about 4-5 hours, I can get it up to 65F. I picked up another one on amazon for $89, it doesn't get as hot as the HD one, but it does throw heat. I mounted that one on the other side of the shop to warm it up a little faster. Certainly, electricity is not the cheapest option, but I don't need the shop 75F and the cost of the heaters and was much cheaper than the cost of a natural gas system and installation.

http://www.homedepot.com/p/Fahrenheat-5-000-Watt-Unit-Heater-FUH54/202043073
http://www.amazon.com/gp/product/B002SG7EWG?psc=1&redirect=true&ref_=oh_aui_search_detailpage


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## redryder (Nov 28, 2009)

Since your post is about woodstoves and dust concerns I can only really speak to that. I have had and used a woodstove in my shop for 23 years. Since I have been retired for the past 8 years I use the woodstove at least 5 days a week during the winter months, say November to March. I have a HF dust collector but I have never done anything special to keep the dust away from the woodstove. In fact I am sure my shop has as much or more settled dust at any time than anyone else's. I have "The Hot One" I think it's called, electric forced air installed up high on the wall but I rarely use it.

One of the great things about a woodstove is the way it sucks the moisture out of the air. As in keeping the moisture content low in your wood. You may have read that many people with woodstoves in thier homes have to have some form of steam to keep them from drying out too much. I can see why city folk may not have a woodstove due the lack of available wood (logs to burn). Scraps are nice but that isn't going to get it done alone.

Bottom line: Go for it if you can. I think you will like it…..................


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## kelvancra (May 4, 2010)

Doesn't take long to make insulating a little at a time seem like an excellent idea. I don't have any rock on yet and only have 3-1/2" in the ceiling. Still, I've been able to work in comfortable conditions all winter. Before, like you, I blew through five gallons in a couple days and it was still a bit too cool.

Prior to my current shop, my old one was heated by wood for ten years. You'd have to have some significant dust - in the air - to create an explosion. I just cleaned up around the stove regularly and blew out the rest of the shop (squirrel cages and electric leaf blower). Did that before the fire was brought up to steam.



> Thanks, guys. One thing I forgot to mention, too, is with regard to economics. Because my shop is not insulated, it seems the jet heater (not sure what the actual name is….I ve seen turbo jet and portable, but would be interested in other names, as well) goes through an awful lot of kerosene fuel. During one cold snap, I went through five gallons in a matter of a couple of days, and the shop never really got all that warm.
> 
> Anyway, I also found a website forum (http://forums.finehomebuilding.com/breaktime/general-discussion/wood-stove-wood-shop) that kind of shows the wide range of opinions on this. I do appreciate you guys weighing in on it.
> 
> ...


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## slimpickens (Jan 21, 2013)

I heat a two car garage size shop with a propane heater (open flame). I do create a lot of dust at times but am not concerned about flash fires. To create that environment, you would have to have a dust cloud similar to throwing a five pound bag of flour in the air. I am more concerned with carbon monoxide but my shop is not air tight and has the required ventilation for a California garage.


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## Tennessee (Jul 8, 2011)

Mike I love that shop, what I can see of it. Very homey…(and yes, I love the woodstove - great place to keep the coffee pot!)


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