I have to type this all over again because the site is case sensitive so here it goes.
The wall that seperates the garage from living space is an area separation wall that can have a 3/4 or 1 hr rating. This means that this particular wall design has been tested by companies like U/L and they have determined the resistance to fire and heat is good for a certain time period. When the wall is tested certain allowances are made for outlets switches etc. and are tested accordingly. The plastic boxes with the 2hr rating embossed on the inside of the box, have also been tested in these walls, and the electrician can tell which box he can use and where they can be installed in relation to other outlets in the same wall. This information is all found in the listing and can be looked up in the white or green U/L directories. The metal boxes have been tested by category and not by manufacturer and all are restricted to 16 sq in in size. Some 3 gang plastic boxes have been listed for 2 hr walls and Allied has had a 3 gang box listed for a two hour wall with another 3 gang allied box back to back. So its all in the listing when it comes to plastic boxes. Caution should be taken when installing a flush panelboard in this fire rated wall - on either side - because there are no fire rated panelboards manufactured.
Your question is a good one and should be taken seriously by other electricians and other trades as well. This wall is not just "another" wall. You can check out the web sites of the Gypsum manufacturers - they contain a lot of information for the asking.
