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How Much Dust?

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  • How Much Dust?

    OK, I'm in Ohio and of course I'm Freezing

    I've heard about dust and the open flame (gas furnace i got, kerosene heater i got propane heater i got) of course all open flame ) I keep the shop pristine. no dust & shavings on the floor and the air cleaner runs 24 hrs most days. how much dust are we talking here as far as spontaneous combustion is concerned ?


  • #2
    I have a ceiling mounted gas heater in my shop. When I first bought the place, I had the same concern. I vacuum my shop often but I don't have a filter system yet and haven't had any problems. I will use my airhose and blow the heater down in the spring after turning off the heater and pilot light. Hope this helps some...
    If at first you don't succeed, try reading the owners manual.


    • #3
      Myth busted?

      I think the Mythbuster guys (you know, those wackos on the Discovery Channel?) did this experiment a couple or three years ago. They played with a variety of different atomizers and delivery systems to distribute sawdust in a closed container with an ignition source. I don't remember what mix they finally had to use, but it took them several tries to get the dust to flash over.

      I'm not an expert in combustion, but I think reasonable housekeeping procedures should mitigate the risk quite well. Even with my dust collection system, my shop can get pretty dusty at times. There are always little piles of sawdust and chips laying around here and there, and the occasional splash of oil. I keep it reasonably swept, and I keep the door to the gas furnace and water heater closed (not airtight, but it helps).

      I guess you'll know I had a problem if you smell smoke on my next posting.


      • #4
        I could be wrong but I don't recall ever hearing of a case of spontaneous combustion where sawdust was involved. As long as you keep your work area fairly clean and don't let sawdust build up around the heat source I doubt if you'll have to worry about your shop suddenly bursting into flames. Oh yeah, YRMV.
        I decided to change calling the bathroom the "John" and renamed it the "Jim". I feel so much better saying I went to the Jim this morning.


        • #5
          Hey Bd,

          What's Yrmv?


          • #6
            I'm not big dave, but I believe that stands for "Your results may vary".

            Dave is using the hip and politically correct method of communicating, "Go ahead and do whatever the heck you want to, just don't come crying to me if it blows up in your face."




            • #7
              Well.............that for sure is the first time in my life that I have ever been accused of being politically correct. But, I am hip enough to know what gaadwthywtjdcctmiibuiyf means.
              I decided to change calling the bathroom the "John" and renamed it the "Jim". I feel so much better saying I went to the Jim this morning.


              • #8
                Sawdust explosion

                My recollection of sawdust danger is that it is very very explosive if packed tightly together in large amounts. Hence the ground wire on dust collection systems to move stray static electricity to ground rather than through a pile of sawdust contained in your collector. Sawdust laying around on the ground is not the threat. It is when there's lots of it packed tightly together. Keep your work area reasonably clean. Sweep and vacuum up the stuff on a regular basis and you should be all right. A bigger concern I would have is cloth or heavy paper type rags soaked in cleaners or oils (linseed oil especially), and then left lying around. Spontaneaous combustion can occur there very easily. Store soaked rags in a metal container with a metal cover. And outside storage away from a building is preferable. If it should ignite it doesn't flash over to anything else. In a garage (shop) I'd be more concerned about that gasoline can stored in a corner. Gasoline fumes are highly flammable and will sit low on the floor. If they eventually find a source of ignition look out. They'll even migrate down to a basement level if the garage is attached to the house and seek out the pilot light from furnace or hot water heater. Take care.
                Jim Don


                • #9
                  Dust Explosion/Combustion

                  I think the hazard here is the possibility of a dust explosion. Fine, combustible dust (saw dust, wheat dust...) when suspended in the air can result in a flash over explosion, if there is an ignition source. This used to be a real problem with grain elevators (maybe still is).

                  This is a different mechanism than spontaneous combustion. Spontaneous combustion results when some material (e.g. oil soaked rags) generates its own heat, to the point of reaching the ignition temperature.

                  I don't know what concentration of dust is needed for the flash over to happen. I would guess this may be more of problem with a heat/ignition source that does not have forced ventilation through the combustion chamber. The dust particles need to be fairly fine/light to stay suspended in the air.

                  I remember demonstrations in science class (jr. high type) where a lighted candle was put inside a gallon can and dust (wheat flour) was injected with a rubber blub. It made a satisfyingly loud bang and flash as the top of the can was blown off.

                  How much of a problem this is with typical wood working saw dust and the various types of heaters, I've no idea. I'm guessing that sanding dust is worst than saw dust, its finer/lighter. It is enough of a concern to me that I've never considered using an open flame or hot electric coil heater in my garage/workshop.


                  • #10
                    According to Bill Pentz, you'd probably gag on the wood dust before it reached the proportion to flash over. Sorry to pick on ya Bill, I enjoyed reading your site on woodshop dust. Still, I just throw on an couple of tight sweatshirts and don't worry about the heat. Of course, I'm in southern NC, so it doesn't get much below 50 in my garage/shop/toyroom/storage area/laundry/everything else that doesn't fit in the house.
                    Only a surfer knows the feeling. Billabong ca. 1985 or so


                    • #11
                      I second that. I usually have the garage door open a crack anyway, to help with ventilation. I'm a big guy, and I like wearing my old quilted flannel work shirt when I'm puttering around in the garage/workshop, so the cool temperatures don't really bother me. It was -11 F windchill last night, but I was comfortable in the workshop.

                      Of course, I have to make adjustments for glue-ups that don't like the cold. Fortunately, I have an understanding wife that will let me bring glue-ups into the "civilized" areas of our home. I've got a couple of guitar stands curing on the living room coffee table as we speak. You gotta love those understanding wives.


                      • #12
                        I seem to be posting this particular link a lot..



                        • #13
                          I guess it can happen, but I was a Body&Fender/Combo man for 12 years, most shops use standard ceiling mounted gas fired furnaces, not even the explosion proof kind. We painted cars without the use of a spray booth even in some shops I worked, I bought my home 15 years ago , detatched garage was insulated and natural gas wall mounted heated,(BIG reason I bought the house) I did alot of body work & auto painting in the garage with no problems, complete paintjobs before the use of HVLP( high volume low pressure) spray guns were used. To the point of there being a HEAVY fog in the garage.I'd crack the window open and use a cheap box type fan to blow it out in winter. I would say wood dust isnt going to be that much of a problem. It could happen, but is HIGHLY UNlikely. I just installed a new ceiling mounted natural gas fired furnace in my garage and I am not worried about sawdust causing an explosion, I do have a DC unit and a JET air cleaner , more for keeping the shop tidy and my lungs less filled with the dust. Not for fire concerns.


                          • #14
                            My guess is that one man could not produce enough dust to cause an explosion, you'd probably choke on the dust before there was enough to go boom.