Kitchens – Over the range microwave venting

You used to be able to buy microwaves that you could apply cabinet facing to, but a quick google search doesn't show any examples.

There are a number of ways to put a cabinet door over a microwave, and it looks like the following would probably suit your needs best:

http://www.houzz.com/hidden-microwave

There is cabinet hardware that lifts the cabinet door out and up, so if properly mounted you can have the bottom venting portion of the microwave open for the stove, and cover the rest of the microwave with the same cabinet facing you have in the kitchen. You just lift it up to access the microwave.

Adding a filter onto an HVAC unit that's not designed for one will almost certainly cause problems... definitely with efficiency, possibly mechanical problems as well. If your model does not have a built-in filter you would probably be better served by getting a standalone air filter.

However, many units do have at least a basic filter built-in, and you may be able to clean it or replace it. Typically they are on the input side of the unit, to remove any particles or debris before the air passes through the unit. If you have or can find a user's manual, check there for instructions. Or it may be obvious once you start looking. In the USA they are often large square filters that come in standard sizes and slide into the unit, but on a smaller model like a window unit it may be a non-standard size. I do not know anything about HVAC equipment in China.