Then you'll be impressed: http://www.3m.com/us/office/advisory/DusterFAQs-fromInhalant... ; http://www.3m.com/us/office/advisory/3MDustRemoverAv152aMSDS...

My understanding is that this is because a typical compressed air can could not actually withstand the pressured required to hold normal air, compressed.

Compressed air is definitely cheaper than any other gas you could use, but you can't liquefy air at room temperature, at least not reasonably. As result, a can of compressed air would have very low capacity compared to a gas which can be liquefied at room temp.

A gas like propane for your BBQ liquefies at room temp, and once it's liquid you can put a lot of it into a cylinder without increasing the pressure.

That's why compressed air is not used in the spray cans.