We are installing cut in type recessed cans and I was told that our lights must be a minimum of 3" away from the ductwork in the ceiling. Just curious where the gentleman may have got that information...is it an NEC requirement that I'm not aware of or is this just a common practice type thing?? Or maybe just a local requirement?? I understand if non-ic there can be no contact but was just curious about the 3". I want to have a solid reference to teach in the future.