Building inspectors do not care about your microwave, or your oven, or your dishwasher, or a whole manner of other things. The architect or construction manager on site has the job of tending to all the details. This means, generally, that they really don't bother with details. They do enough to get the job done. That's it. Things like usability and proper installation tend to fall through the cracks in the rush to meet deadlines and budget constraints.
I have a brand new microwave. High wattage, well, more than what I'm accustomed to. If I open my mouth near the door during operation my fillings spark. Some would call this a problem. I call it fun. It's an over-the-range unit, GE. Quite the space saver. I like it a lot. Like all over-the-range units it has incorporated into it a vent hood with lights, a fan and the obligatory oil filter. I was looking at the fan, and I knew from the conspicuous absence of a vent shaft that the hood did not vent to the outside. Like most apartments built around here the microwave recirculates its air back into the kitchen - smoke and all.
After an exhausting afternoon chasing down spiders with my Dustbuster I sat down with a cold beer and started reading my appliance manuals. You do read your appliance manuals, don't you? Specifically the microwave oven. Since I never had such a fancy unit I wanted to thoroughly understand what it could do. The folks at Mayo Group were thoughtful enough to leave both the installation manuals and the operation manuals. I decided to peruse through the installation manual since my experience with other aspects of my new home indicate that Mayo Group workers don't really read them even though they are also in Spanish, French, and German. To my great surprise the microwave was installed correctly. Then I noticed some fine print. Under a configuration diagram there is a note that the vent filter is not part of the standard installation kit. It's something one must order separately if installing the microwave in a recirculation configuration since the standard configuration is for attachment to a vent shaft. Since I know Mayo is cheap and Mayo workers have no attention to detail my suspicion said that the vent filter is missing. I removed the vent cover to inspect my filter - nothing.
The vent filter is a charcoal and fiber filter that fits into the exhaust cavity behind the vent fins above the microwave door. It is not the metal panels that fit into the fan intake beneath the microwave. Those are the cooking oil vapor filters. To access the vent filter you must remove the vent grill. Upon its removal you'll see that the filter sits at an angle inside a center cavity, and notations embossed into the sides indicate how it should sit. The manual has a part number for the filter, but you'll never find the item in the store. Instead just pick up the generic rectangle of a filter at Home Depot that says it will fit most GE microwaves. Hotpoint is essentially the same design. The filter will remove a noticeable amount of smoke and save you from getting oil vapors blown onto the vent fins where they'll slowly turn into mother natures version of brown sticky plastic. It's not as good as having a real vent, but it's better than the alternative.
Check your microwave.