i know what they're talking about in that. sometimes old wool takes on a distinct crisp, yet organic old-age smell. This is usually very, very faint unless you're right up to the pile of the rug with your nose. I don't know how to describe it other than it may carry a very slight odor of charred wood. again, you have to be really close to the rug to smell it, and other characteristics come with that such as a drier feel to the pile. not necessarily a bad thing or overpowering, but not the greatest if you plan on having that antique rug in a high traffic area. usually an indicator of exposure to dry environments or just old age. Old wool odor, burnt smell, etc. don't really indicate structural problems in a hand knotted rug (burnt smell for hand tufted is not good - usually means the glue is past lifespan) however...
Musty smell or anything with a more lingering odor which is powerful indicates a serious underlying problem in almost any rug. Dry rot you can't always smell if it's been cleaned or dried quickly, but any of the musty smells, or mildew often indicate a serious structural problem in the rug or quick attention needed. This may result in holes, hard spots, or areas where the foundation has become brittle and susceptible to damage.
