I've posted many times. Look at the sky. If you would allow roofers to take the roof off your house to do work, then it is safe to work in your bees. If you wouldn't allow them to, the bees aren't going to allow you to take their roof off either. The worse attack I have ever had from a hive was when you could see the clouds on the horizon and smell the rain coming in, but it had not gotten there.