I’m with Brudgers.
The 2009 IMC is pretty clear (clear that is except for the “commercial purposes” thing – more in a moment) that once it has been determined that the use of a residential stove is a “commercial purpose” you have no flexibility in the type of hood required. A Type I hood is required for any medium duty appliance, no discussion of smoke or grease (this is a change from 2006). Per the definition of a Medium Duty Appliance, anything that uses a hot surface for cooking , including a hot plate, a Kenmore stove, or a George Forman Grille is a Medium Duty Appliance. This is because the code, as brudgers pointed out, recognizes that the only reason you need a hot cooking surface is to make grease and smoke. If you don’t need to make grease and smoke, use a microwave.
The commercial purpose thing could have been better defined, but I do think there is a definition within the IMC that can be used consistently by an AHJ. The definition of Commercial Cooking Appliance includes “For the purpose of this definition, a food service establishment shall include any building or a portion thereof used for the preparation and serving of food.” Two things are required to be a “Food Service Establishment”; 1) preparation and 2) serving. If food is prepared on a Kenmore range and then served, it is a food service establishment, and it is not that big a leap to say that a residential appliance is being used for the same purpose that a Commercial Cooking Appliance otherwise would be. This creates a bright line that an AHJ can use – if the use is just so Bob can make lunch and feed just Bob, it is not Commercial Purpose. However, if Bob serves Ted, Carol, and Alice it is a Commercial Purpose.
Yes, the above method requires believing the Owner’s description of the use of a space, but this is common throughout the code, such as the fact that the sofa in the night watchman’s office is just for when buddies come over. I think this will separate most cases into obvious categories: stoves in office or factory lunch rooms or employee break rooms – not commercial. Stoves in church assembly halls; child care facilities; fire stations; bed-and-breakfast lodgings; VFW and similar halls; cooking classrooms; cooking demonstration displays, and charity soup kitchens – commercial.
There will always be the grey areas, such as a stove in a rehab healthcare facility used by patients to re-learn skills, or group homes. The users may cook just for themselves, but there could be a lot more meals prepared than a typical SFR.
