When should you wear a facemask for safe breathing?

After spending some unexpected time crawling around in a roof today fitting some lights and greatly disrupting and breathing the insulation (and getting itchy all over) I started wondering about this.

Anyone know what's the dangers from things like:

sanding(wood/gyprock/paint etc)
spray painting
roof insulation
dust

Carcinogenic? Lung problems?

And if protection should be used what style is sufficient?

Thankyou.

Mate that is more than likely fiberglass insulation bad move with going up there without protection, I would have had a dust mask & disposable overalls + a cap minium. The main concern is the fibres.
Lifted from a yankee website:
Literally hundreds of studies over the years point to the fact that the microscopic shards in fiberglass dust have led to pulmonary problems all over the world. If you've ever come in contact with fiberglass, you already know what it can do to your skin. The tiny fibers of glass from insulation wool can irritate your skin and eyes. If you experience too much contact with fiberglass, it can cause what's called irritant contact dermatitis, or inflammation of the skin. Breathing in fibers can also increase the difficulty of breathing.

I had to spend a day in our roof, fitting a couple of ceiling fans. I didn't give it a seond thought - it was hot and I was up there in shorts and without a face mask. I subsequently spent the night in hospital barely able to breathe!

If I'm going up there to have a quick poke around or wire another antennae outlet into the splitter, I won't bother with a face mask. Any longer and I'm in my tracky's, jumper and mask.

Thanks for the replies

I'm glad I only spent about 10 mins up there routing the cables. I suspected it wasn't the best after seeing the fibres flying around in the light, but luckily I didn't suffer any problems except itchy arms which went away after a shower

Damn Aardy hospital, Ouch!

Well we know what not to do now

How about sanding paint etc? I think I'll just be applying the "if in doubt, use protection" philosophy..... always a good idea

Make sure you always have protection on!

When I installed my Home Theatre I was crawling around in the roof sometimes on my belly
breathing in all that shit and knew full well what the dangers were.
I always just think to myself, Life is to long anyway and since I'm married and on my
second lot of kids, I'm just "marking time until I die".
There are no warning signs about it so maybe the kid's will get a James Hardy type compo
package and live happily ever after

only prob with that condo mask is when the air runs out you have to rupture it

as for your four queries on tasks to wear a mask or respirator
yes
yes
yes
yes
with allowances for bravery and short term work situations