Wow, sometimes you folk split off in so many different paths it's hard to follow. The following is based on the 2015 IMC - Electric pizza oven (enclosed), Type II hood unless heat and moisture loads can be incorporated into HVAC system per Section 507.3. Gas pizza oven (enclosed), Type II hood (produces products of combustion per Section 507.3). Electric or gas pizza oven (conveyor), Type I hood (see mtlogcabin post referencing 2012 IMC - 2015 hasn't changed). Convection oven (enclosed) (tested through UL Category KNLZ which BTW uses pizzas to conduct the test), no hood required based on Section 507.2 Exception (that was for you cda). These are generally small, countertop installed cooking appliances. Solid fuel fired pizza oven (required to be open to operate), Type I hood per Section 507.2. I think that covers all of the different ways to cook pizza.