Duct Detector Annual Testing

We are reviewing our practice of fire system testing and have a question. Can you clarify whether we are or are not required to set off individual air handler duct detectors and confirm air handler shut down for each annually or could we put the fire alarm system in bypass, smoke each detector, and confirm that it has been acknowledged at the fire panel?  (We currently do this once each year.)  If we had to have each air handler shut down, we would be shutting down 67 units 67 times, creating a nightmare and a life safety issue in its own right. Actually every air handler has two, a supply and a return, making the issue even more paramount. Can you shed some light on this vital issue?