In some cases the use of a hair dryer is recommended by the instructor. However, in a workshop setting consider the problem of two to ten hair dryers shrilling away, paining ear drums and hearing aids. Don't give up the benefit of your hair dryer, just find an outlet away from the crowd in some cases a place just outside the door can be ideal for these things. If there is only one outlet outside the classroom consider gaining brownie points by offering the use of your dryer to anyone else who might need it provided they leave it outside the classroom. Never take photos of the models whether nude or clothed without asking the model first.
Some models hired by workshops are professionals.
Their image is protected under the copyright laws. One of which is the comfort of the models themselves. Always expect a nude model classroom to be warmer than you feel comfortable. Plan on wearing clothing that is layered. What may seem warm to a person with a sweater would be chilly to someone without.