If you are seeing 100 sf per person recommendation, that would most likely include space other than the student’s lab, such as prep areas, stockrooms, offices for lab managers, equipment and chemical storage, etc.  24 students plus instructor would be 2500 sf, which is larger than my 4-bdr house. I was recently in a lab in which the architect took the 75 sf per person recommendation literally and there were 3 resin-top benches, each with drawers and space for 4 students per side.  The aisles between the benches were 10 feet wide, as was the aisle at the back.  The aisle at the front was 20 feet wide.  The room gave the impression of a couple of card tables set in the basketball gym.

We had discussions about changing enrollment caps on some of our labs several years ago.  Our enrollment caps are coded into our registration database and we cannot enroll more people in a room than allowed by the campus Fire Marshal.  He asked that I speak to the consultant for the International Building Code who wanted to know the number of square feet that was totally free and unobstructed by shelves, hoods, lab benches, racks for backpacks,  safety showers, chalkboard ledges – anything that might impede egress.  He also asked for the overall dimensions and perhaps asked about the presence of fire suppression sprinklers and the ratings of storage cabinets before he provided a recommendation.