Vapour Combustion


So we've sorted out that dust is likely not a risk for combustion in the home workshop unless you're shaking out your dust collector bags right beside your furnace/ hot water tank pilot light.
Now for the vapours....I try to keep to the water-based stains, paints, etc, but every once in a while resort to an oil-based. If I'm using an oil-based, I crank the basement window open (basement shop). I recently purchased a cartridge-style respirator with organic vapor filters for lung protection. Do I need to be worried about an explosion from these vapors? What sort of concentration is required before the flame will make a big 'poof.'
I was planning to use some contact cement on a project. I had purchased latex CC, but advice from this forum recommended oil-based CC. Based on the warnings on the can, I'm thinking maybe this stuff should stay out of the basement shop.
On a slightly different note.....
I need to attach oak skins to kitchen cabinet sides. How dangerous is this stuff to use on a main floor kitchen. I would close the basement door to prevent the vapours sinking to the basement, and set up a fan with windows open to exhaust the vapours.
Thoughts?
Steve
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explosion from these vapors?
Typically NO, but you do need ventilation and for occasional home use a window fan used in a window for exhaust will work. IF you are spraying then you "may" have explosion considerations.
Oh, keep in mind "organic vapor filters " will NOT protect you against Isocynates which may be contained in some products such as polyurethane.
--
Rumpty

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Rumpty wrote:

Isocyanates _will_ be contained in _all_ polyurethanes including waterborne, and will not be contained in any other kind of coating, as by definition isocyanate-based coatings are polyurethanes.

--
--John
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and will not be contained in any other kind of coating, as by definition isocyanate-based coatings are polyurethanes
John thanks for the clarification, I'm a ISO freak who has had bad dealings with them. That's one reason why I use Hydrocote Resistane as a finish as it doesn't contain ISO's.
Inhale deeply......
--
Rumpty

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Rumpty wrote:

I remember the day that one of my former employers lost one of their minor but irreplaceable corporate resources--there was a painter on the propeller blade line who had been with the company over 30 years. He could put a blade on the balance machine, check the balance, move it to the spray booth, put a coat of paint on it, and it wouldn't need final balance (which is intended to adjust for the weight of the paint) afterwards--he could eyeball it that precisely. After spraying polyurethanes for 15 years or so, with a good spray booth but no respirator (it was Fortune 500 Aerospace and they do things like that right or not at all, but the safety folks did their thing and the numbers said that in that booth he didn't need any kind of protection), one day his system decided that it wanted to be allergic to the stuff and he couldn't even come into the factory anymore (building is about a quarter mile square) without going into anaphylactic shock.
That's the insidious thing about isocyanates--not that they're immediately toxic but that when your system decides that it's had enough, then you can't even get _close_ to them. And when that point of sensitization occurs seems to be random--one guy can spray his whole life without any protection and never have a problem, another guy can get sensitized the first time he forgets to wear his air mask.

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--John
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J. Clarke says...

It was a methyl isocyanate leak that killed over 2,000 people in Bhopal India.
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Hax Planks wrote:

Enough of _anything_ will kill you outright. Most of us don't release 40 metric tons of pure isocyanate at one time.
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--John
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J. Clarke wrote:

Just how big was Norm's Highboy project?
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I have a business associate I probably see a few times every year, a new young furniture maker, last fall I asked what finish do you use, he answered "wipe on poly" well as soon as I heard that I went into my ISO rant. I recently saw him at a show and first thing he asked was what waterborne finish I was using. I asked why? He mentioned that his wife does the finishing and she developed "mood modification" after finishing, i.e. she would argue and get POed really easy. Mood modification is another ISO reaction.
I haven't sprayed poly in 20 years due to sore throats and mood modification. I have on a rare occasion sprayed a fender or two on the family car, and after spraying a hardened auto paint, my throat hurts....20 years later and same reaction.
--
Rumpty

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http://www.ilpi.com/msds/ref/flashpoint.html
For the basics. Normally that will appear on the container, as well.
Problem with some vapors is that they are enough heavier than air to hang around close to the floor. Thus the of-repeated warning to use in a "well-ventilated" space, which is meant to describe conditions where they are mixed with a great volume of air, rather than waiting for that casual spark in some low area. More for protection of your hide than lungs.
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Brushing does not seem to be a problem as not enough vapors are released in one application. Venting is still a good thing. Spraying is a different story as the solvents are more atomized.

YES. Many a kitchen has burned up when the contractor used CC to install countertops.

See note above. My sister's new kitchen was done except of the counters. POOF!
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Mr Fixit eh says...

It all depends on what the solvent is and how much is used. The risk from exploding vapors from mineral spirits is pretty much zero. Contact cement includes hexane, naphtha, and acetone, all extremely volatile and potentially hazardous, especially hexane. Hexane is similar to but only slightly heavier than the butane used in Bic lighters. It's about as bad as it gets for risk of vapor combustion. Good ventilation is absolutely essential, but obviously it can be used along with common sense. Your ventilation plan should be plenty. Naphtha isn't a chemical, but it is usually a mixture of mostly alkanes (hexane is an alkane, as is butane and propane) and some other aliphatic hydrocarbons falling somewhere between gasoline and kerosene in volatility. It is excellent for cleaning wood prior to finishing, but use with caution if the space is small or sparks or fire may be present. Most of us probably already know acetone is extremely volatile. It has been the bane of many a fiberglass factory. Lacquer thinner contains acetone and nitrocellulose is explosive in its own right, so spraying lacquer in a booth is literally like standing inside a bomb. I don't want to sound paternalistic, because even basic precautions are usually all that is needed, but everyone should know what can happen so they make sure it doesn't.
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Mr Fixit eh wrote:

I once saw a woman in the ER who was blown through the CLOSED door out into the yard while she was using contact cement to surface counter tops. The water heater pilot ignited the vapors. She was not seriously injured but the windows were.
--
Gerald Ross
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In general, worry about the hazard from you breathing it, long before you need to worry about explosion hazards.
The crucial factor is the concentration, and whether this is in a range that forms an explosive mixture. For typical workshop use, this just doesn't happen. If you're insistent on blowing yourself up, best way to arrange it is to either knock the can over (suddenly raising the concentration far beyond what you expected) or to have an ignition source close to where you're working (concentration will be highest around the can, or a large freshly glued/painted area)..
The significant concentration varies, depending on the chemical in question. For our workshop solvents, you need a concentration of at least 1% to form an explosive atmosphere (unless you're using some plutonium and hydrazine process for staining cherry). This is unthinkable in the workshop at large, but it's easily done near to a pool of liquid solvent. So keep a good physical separation between your solvents and your ignition sources ! This includes low-mounted pilot lights and heavy vapours (like propane) that will concentrate either on the floor, or below the ceiling.
There's a handy list of flamable solvents here: http://ptcl.chem.ox.ac.uk/MSDS/lowflashpoint.html This lists the explosive limits, but it also lists the flashpoints. Flashpoint is perhaps more useful here - if you're using a liquid with a low flashpoint (around room temperature) then the vapour above a pool of it will be an explosive mixture. This is where the definitions of "flammable" and "highly flammable" come from - "Highly flammable" will do this at room temperature, "Flammable" will do it with just a little warmth (like a nice hot cup of tea)
Paint solvents are generally flammable. Glue solvents are often highly flammable. be careful with paint, but be _really_ careful with solvent based glues. The "construction adhesive" in mastic-gun tubes has an infamous reputation for this - something like 75% of vapour explosion accidents in construction are caused by this - not petrol, not paint thinners. If toluene is an ingredient, be wary.

This is called "veneer" and you do it with hide glue (ideally hot, but the cold stuff is useful too). Now I'm a hide glue fan because I still think it's the best and easiest way, but I appreciate others will have their favourites. However anyone will tell you that doing this with contact cement is a royal pain to do, let alone the vapour hazard.
Oh, and vapour exhaust fans need to be of a motor design that doesn't use sparking brushgear ! (most are OK)
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