I know cal osha requires everyone at all times needs a hard hat on a construction site. I don’t work small private residential cal osha may be more strict on bigger jobs but it is an osha requirement here so I assumed it was a federal osha policy. I know it was definitely covered in my osha 10 and OSHA 30 courses. I was also an instructor for my trade union and this is what is taught in the nationwide union curriculum and yes any heavy equipment we use we have to wear a hard hat while operating nationwide In my trade.