There was a disucssion on exactly the same topic in the Mechnaical codes sections just a few weeks ago:
For your convenience, I'll reprint my reply from that thread:
The key phrase in IMC section 507.2.3 is "utilized for commercial purposes." The section says that if a domestic appliance is utilized for commercial purposes it needs a commercial hood. The corollary is that if a domestic appliance is NOT used for comercial purposes, it does NOT need a commercial hood.
The IMC does not define "commercial purposes" or even "commercial". That means that the common dictionary definition determines the application of the terms. Any dictionary you consult will define commercial as having to do with producing or conveying goods to a MARKET, usually involving an exchange of money.
The conditions and purpose of the facility described in JSW's initial post do not suggest that there is a commercial purpose involved in the use of these appliances. They are there for the training of students in cooking food for domestic consumption, using equipment likely to be available in the home. There is no indication that the food is being produced to supply a market or to exchange for money or any other item of value. This is in clear contrast to, for instance, the school cafeteria, which unquestionably produces food for a market.
Based on this I don't see any way that a requirement for a commerical hood, either Type I or or Type II, can be justified.
Also note that there is nothing in the listing of a domestic appliance that prohibits it's use for domestic-type purposes in a location other than a household. This is a common misconception. The key is not the location, but the type of usage. Just like a microwave in the break room of a commercial establishment is not being used for commercial purposes (and IS being used in a way typical of a home) a domestic range in a school Home Ec room should not be treated as a commercial appliance just because it isn't in a house.
A domestic range being used for non-commercial purposes does not require either a type I or type II hood, regardless of the occupancy in which it is located. The key is the type of use of the appliance, not the location. The possibility of frying chicken in a break room doesn't trigger the need for a commercial hood any more than does the possibility of frying chicken in your home kitchen. The people who wrote the code were very careful to draft the language to express this intent. There should be no serious suggestion that a commercial hood is needed unless there is compelling evidence that the appliance will be used for commercial purposes. Such eveidence hasn't been suggested in this case.