I couldn't live without a high velocity dryer! I certainly would not have Newfoundland dogs without one. High velocity dryers are safe to use on dogs and blow cool air. It's the best way to get out undercoat and mats.
But, even on low speed they can have too much power to use on a dogs face...so for these dogs we use hand held human dryers, at my Sister's shop we use them spareling for drying dogs faces (breeds that require style). For breeds such as Poodles, Schnauzers, Bichons we use a stand dryer and hand held dryer and brush to straighten, fluff etc. It's hard to get a proper look on some breeds by just toweling them and putting them under a cage dryer. My Sister leaves many of the grooms she does in full coat and she has to blow dry the dogs...especially since she does a lot of dogs for show.
It is important to be careful using a hand held human dryer on a dog especially since even on cool setting they can still run a little too warm. That is my biggest concern is the heat. There are too many people who have burned their dogs with a hand held dryer and that is what I think makes them dangerous.