Mr Fixit eh says...

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.

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.