It is preferable to draw air away from the keyboard rather than to blow air onto it. In particular, beware of industrial-strength air compressors or "house air" in labs, etc., as these often contain oil mist from the compressor. If you are in a lab setting, you can use the house vacuum (with a trap) or a water aspirator pump (with a trap).
most modern house-sized compressors are oil-less and use fluorinated polymer coatings on all motion assemblies. shop air that isn't driving air tools is generally assumed to be "clean and dry", and air that drives air tools is assumed to be clean and dry with lubricant aspiration. long ago, this may not have been true, but modern resins make it much cheaper to build filter, coalescer and lubricant aspiration assemblies that are compact and have high WPs.
anyway, the metro datavac series uses filtered air (more so with the mdv series, with fine toner bags and hepa filters available), and is low enough pressure that it doesn't need a coalescing filter. as for sucking vs blowing (sigh, go off and do your tittering kids..), sucking up small particles requires increasing pressure somehow, while blowing off small particles can be done with high velocity, so generally, blowing is better than sucking for clearing out obscured assemblies.
