It looks like there are two new room categories popping up at some properties-- the "Respire" rooms are the hypo-allergenic rooms. I've also seen a new room category of "Smoking". Here is the description of the room from the GH SF:

Introducing a new smoking room experience. Discover an environment where the air can be continuously filtered to dramatically lessen odors commonly associated with smoking rooms. This room is perfect for those travelers who smoke but want to enjoy a fresh, clean air atmosphere.

Both room categories seem to be priced the same-- in the case of the GH SF, it's $25 more than a base room.