There is ongoing thread about fire extingusihers (feedback on FWW).
But I thought it might be useful to bring the topic of fire hazards over here — by way of asking these general questions:
1) Aside from the dangers of spontaneous combustion, what are the other potential fire hazards in a shop?
2) If your dust collection system is properly grounded, does that completely eliminate any fire risk?
3) I have always been told that it is best to keep solvent based finishes in a metal cabinet. But if you don’t, what are the potential risks — assuming these materials are removed from any ignition sources (such as boilers and hot water heaters)?
4) I have been told you should never spray volatile materials such as lacquer in a closed shop without heavy duty ventilation, and preferably a proper spray booth. But are there any dangers in spraying any of the water-based materials?
5) Are there any fire experiences (workshop related) any of you would be willing to share?
Replies
Several years ago I was cutting some 'salvaged wood' (Oak pallet wood) on my table saw. I always use a 'junk' blade for this operation. While cross-cutting I hit a nail and got the usual THWACKing sound as one more blade-tooth bit the dust. About an hour later I scooped the sawdust from the bottom of the saw into a heavy duty plastic garbage can and left the shop. Two hours later the smoke alarm went off as a thick plume of smoke came from the sawdust in the garbage can. ONE spark had smoldered for almost three hours! A heavy dose of water from the garden hose took care of the problem. I learn REAL quick. Now I empty the sawdust into a metal garbage can, place a tight fitting lid on it and take the whole thing OUT of the shop. I'm also MUCH more careful in inspecting the wood I cut.
The only thing that was damaged was the garbage can and my pride.
SawdustSteve
WOW! I can't imagine that fire would have started so long after. Ill remember that.
Mike
That's scarry.
That raises the issue of smoke alarms. I have them all over the house, but never installed them in the basement shop -- on the assumption normal shop dust would foul them up.
Does anyone know if that's true?
Now I'm going to add the smoke alarms by the door of my woodshop....
re: smoke detectors
I have them outside the shop proper too. But I am still wondering if I should be installing them in the shop itself.
On the other hand, it wouldn't be hard to wire one up and see what happens.
Another possibility would be to take the cover off so you can dust the works with a soft brush as needed.
And a second thought ------
You obviously weren't using a dust collector. And I wonder if it is possible for a spark at the table saw to travel through the DC pipes and continue smoldering?
I'm not an expert in combustion, but I'll offer thoughts to your questions.
I would think that a piece of hot metal, small as it is, would cool off enough in the travel through dust collection ductwork with all that air movement that the risk of fire would be greatly reduced.
I always use only a metal trash can with a tight fitting lid. I keep it away from the wall in the center of the floor when I've put sawdust in it.
My guess about putting solvent finishes in metal cabinets is that it is safer for two reasons. First, if there were a small fire it would take longer to burn through a metal cabinet than a plastic or light wooden one. If the doors closed fairly snugly without louvers then any fire would quickly use up all the air in the cabinet before it got hot enough to melt, and would be reduced to a slow, smoldering condition that would take a long time to get out of the cabinet, if at all. Second, if there were a leak, a solvent would soak into wood or dissolve plastic, both of which would increase the risk of fire or spilling in the shop.
There's probably no fire danger from spraying water based finished, but the label on the container would be the most reliable source of information.
The only workshop fire experience I had was in junior high school. The welding bench was along the wall beside the painting bench, with the trash can, an open 55 gallon drum, between them. One day a welding spark ignited the solvent and paint soaked rags with a loud whoosh. Putting out the fire was delayed because the fire extinguisher was hanging on the wall above the trash can, surrounded by the flames. It took the teacher a few moments to decide to grab the extinguisher through the flames. Now, many years later, besides knowing enough to not commit the multiple errors that contributed to the problem, covering the can with a piece of sheet metal from the rack would have been a better initial response.
The risk of a spark causing a dust explosion in a residential/ small shop DC system is supposed to be non-existent. But I worry about metal bits getting sucked in. Hitting the fan blades could cause a spark, which could cause a slow smoldering fire in the DC dust bin.
I agree it's possible for a bit of metal hitting a fan blade to cause a spark. But I think the spark would be such a small mass that it would cool almost instantly. A chunk of nail cut through by a table saw, though, would hold its heat better if it just plopped into sawdust below the saw because of its larger size.
The better dust collectors have filtration before the fan so the fan is not in contact with sawdust or other debris.
Someone earlier mentioned smoke detectors. I don't know how badly a buildup of dust would affect them, and I certainly smoke some wood when ripping on the tablesaw from time to time. I think a heat detector would be a better choice for the shop. I wonder what is used in commercial operations.
I took my bandsaw off of the system. The thrust bearing on it is a 2.5" diameter plate with the axis of rotation offset about 1" over from the blade. This causes a shearing action as the back of the blade is pushed against it. I had never noticed the sparks until one knight I was letting someone else use the saw while I looked under the table to see if I needed to modify the dust pickup.
Whenever I saw all of those sparks, and that fine dust mixing together, I don't know what kept it from igniting. I just took that saw off the system.
Next, I think my greatest hazard is from my pup. He likes to grab whatever I have been using and sneak off with it and chew it up. He knows he is doing wrong, because I can tell by his posture before I find his work, but I can't get him to stop. I am afraid he is going to get a can of spray lube, or paint. He is big enough to grab stuff from the back of the workbench.
I think most impellers are Al. for just that reason
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
I always unplug everything but the dehumidifier when I leave the shop. Is this necessary?
FB
Everything?
I assume you're kidding ..........
Refering to the 5 points in your posting of May 29, I offer the following:
1. Aside from spontaneous combustion there are plenty of fire hazards in the shop. First of all fire is always a potential when you have a fuel (wood in any form, plastic, flammable/combustible liquids, cloth/clothing, paper/cardboard/corrugated paper) an ignition source (heat) and an oxidizer (air i.e. oxygen). The best approach to control or reduce the risk of having a fire is combination of controling ignition sources and good housekeeping to limit fuel near potential ignition sources. Electrical ignition sources from a frayed cord or over heating loose connection. Loose, or high resistance connections can ignite wood dust/shavings, electrical insulation and plastics contained within junction boxes (even some J boxes which are plastic will serve as a fuel for an electrically initiated fire). Vapors from flammable liquids and combustible liquids of course will burn when mixed with air in the correct range. For example gasoline vapors will burn when mixed with air from approximately 1.5% to 7 %, natural gas 5% to 15%, acetone, MEK and other common solvents have similar and broader ranges of flamability and all should be treated with respect. Other igniotn sources frequently forgotten about are pilot lights on water heaters, furnaces and clothes dryers, radiant heat from portable electric heaters. One of the best sources of information about the hazards from a product (including fire) is to read the manual and labels. These folks have been sued for almost every imaginable use/misuse and are warining about it now.
2. I believe if your dust collection system in a home or small wood shop is grounded there is essentially no risk from igntion by a static discharge within the system. I also believe there is little risk of ignition of dusts followed by a fire and/or explosion even in poorly grounded systems in home shops and small wood shops. Having said that it is still best to minimize the risk from fire and inadvertent discharges to people and equipment by properly bonding and grounding.
3. Flammable liquids are best keep outside of the shop if possible in a detached location. If the shop is in the basement of your home under no circumstances would I keep flammable solvents and oil based paints in the house! A metal cabinet is a good idea even if it is not fire rated. Fire rated metal storage cabinets for flammable liquids are available but a secure outside location is a lot cheaper. The real risk in keeping and using flammable based solvent materials is that the vapors these are all heavier than air, can flow (unseen) like water albeit slower and can find ignition sources far away from wher they are being used.
4. You are correct in not spraying flammable liquid based paints and lacquers in a shop or in the house without eliminating all ignition sources. No fire risks associated with spraying water based paint systems.
5. My one shop fire is unusual but worth sharing since it illustrates my inattention to shop safety. My table saw is plugged into a reel extension on the ceiling. On this occasion I did not notice that the way the cord from the saw was draped behind the table but adjacent to the drive belt near the pulley on the motor. I hadn't been in the shopfor about four days when my wife asked me to get something from the second floor stroage area. I went up the stairs and across the floor (directly over the saw and cord reel). As I was coming down the steps I saw intermitent flashing like an arc welder and heard a concurrent buzzing sound. When I turned the corner into the shop I could see the arcing behind my table saw as it continued along with flanes burning up the cord. I turned off the circuit breaker and pulled the cords away from the saw. The fire self extinguised ina few seconds. Examination showed where the cord had been rubbing on the belt and pulley. The arcing was set off by the vibrations walking across the floor and once it started to burn it was easy for the arcing to continue. The lesson for me is to look where the cords are around the shop and make sure they are away from places where they can get rubbed, pinched or receive other damage.
Whew! I wrote more than intended but you can see the passion from a Safety guy
Dr. J
Good, helpful info.
RE: Solvent based finishes.
Obviously, I would think this sort of stuff would be fuel for a fire that started someplace else. But I am curious about the vapors. Is it even possible that vapors can seep out of tightly closed container? And if so, I wouldn't think vapors from one or two leaking cans would be enough material to create a fire if the vapor creeped over to an ignition source (say, a standing pilot in a water heater). Is that right?
Also: Smoke Detectors
I have not installed smoke detectors in the shop itself, assuming they would get fouled up with normal wood dust. Is that true?
There would not be enough vapors from a poorly sealed container of a paint or flammable solvent can to accumulate and reach the lower flammable level concentration. Storage as a cause of a fire is very unlikely. What usually happens is a spill from a dropped can or just being knocked over in advertently. Admiittedly low risk. Of course the other hazard of storage is adding fuel to a fire involving other material. Yes smoke detectors do rely on air (with smoke) moving to the detector either photoelectric or ionization type. The manufacturer will caution about placing the detector in a dusty environment or locations where false alarms can occur, such as kitchens or bathrooms. Heat detectors are a good alternate since they function on rate of temperature rise. Remember however you need an established fire to generate enough heat to set a heat detector off whereas you only need a little smoke. One last point is that smoke detectors are primarily to alert you to a fire if you are not awake or in a different location. You dont need a smoke detector to tell you that there is a fire in your shop if you are working there. You do need one when you are not there if a presents a hazard to your home i.e. if yor shpo is in the home I would have one and clean it regularly.
Dr. J
Here's another one.
My shop is the driveway, with storage of equipment in a shed next to it. Last summer I had cleaned up some sawdust/shavings etc. that had been laying outside next to the driveway. Put it all into plastic bags and set aside to haul to the dump.
A couple of nights later, my wife hears a loud bang. We go to investigate and the bags are in full flame. Turns out the sawdust was a little damp and from being closed up in the bags with the sun beating on them, they had self combusted.
The loud bang was the right front tire on my pickup blowing. The bags were sitting right next to the truck and caught the tire on fire. The truck was old enough that I just sold it for salvage and I got a new one. Hard way to get a new truck though.
I've had a low cost - battery operated smoke alarm in my dusty basement shop for a couple of years. It works just fine, set it off just about every time I rip some wood. It can't hurt to have one. I'm not sure what code is in your area, but if you can just get a battery one if it pukes after a couple of years, get a new one. No big deal.
If it is going off when you rip wood, I suppose we can assume it would do its job in the event of a real fire........ right?
(Have you thought about getting that rip blade sharpened?)
Yup!
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