[Al Skierkiewicz]

Chuck,
The standard finger that Russ speaks of is a test fixture used by UL to test fan guards. As I understand it, the device takes into account the distance from the guard to the blade and the size of the openings in the guard as it would pertain to a finger intrusion. As this is a new concept in robot design for First, and has potential safety issues, I am sure that several different disciplines are involved in setting a standard for inspections.
Finger intrusion is only one of those concerns. As have been discussed above, noise, flying debris, robot damge, etc. are all concerns as well.