Instead of paying big bucks for prepackaged air check out the ReAir refillable air sprayer. With about ten strokes of a standard bicycle pump, you've got a canister full of compressed air to blow crap out of crevices, patchbays, tape head assemblies, disk drives, etc. When it runs out, just re-pump to 100 psi and you've got enough air to clean out one or two devices. Good for 100 refills - good for the environment. You can find it at office-supply stores. $11 for one canister or $13 if you want the package with an included hand pump.