If its in an internal garage, its most likely Asbestos. I've got it in my house, the previous owners put plasterboard over it when they converted the garage into a dining room, which is fairly common.
Got some suspicous boarding in the job i'm doing at the moment on the garage ceiling, it's getting tested. I reckon it's fibre board though, couldn't see any A's written on it. Better safe than sorry.
What do you mean about A's being written on it?
Soffets are usually asbestos on pre 80's houses.
Apparently old plasterboard contains it as well. Some builders recommend overboarding an old ceiling, rather than ripping it down and disturb it. You cant get away from it mate, if you are a tradesman, you will come into contact with it in some way.
I've done the same course Cside mentioned, its surprising how many different products contain asbestos.
Plasterboard, floor tiles, soffets, any sort of internal panel (especially in bathrooms/kitchens), shuttering for concrete (Ive seen this in a pantry in a council house), anything to do with old boilers/fires, ceiling tiles (many old department stores have asbestos tiles throughout (have a look next time you are in an old woolworths, M+S, Debenhams etc)), garage/shed roofs. as well as precast walls,pipework, pipe lagging etc etc.
I wouldnt advise leaving a job just because it has asbestos in it somewhere, although I defo wouldnt be doing any work that disturbs it at all.