We have a high proportion of disabled students on campus.  When we have had a student with a service dog, the dog remained in either a faculty member's office or a nearby computational research lab (both of which were a couple of rooms down the hallway from the lab) while the student was in the freshman chemistry and organic chemistry labs.  The dog was near enough that it could come quickly if called by its owner, but it was kept safely out of the lab.  If the student needed assistance carrying, grasping, or otherwise manipulating equipment an aide would have been provided for her/him.