windapp
Contributor
Technically, you are not supposed to share air. Sharing air is a signal for an "out of air" situation on one of the diver's part, while at depth. This means you immediately start to head up to your safety stop, and lacking a safety stop, go ahead and surface. That's what all the classes teach.
I personally would skip the safety stop in an emergency air sharing situation or at least drastically shorten it, only using it as a chance to ensure a nice slow accent speed for the last 5 m.