Hi Henry, Wow, I can't believe it's been over a month since you posted your message. I've been battling with the crawl space, and I think I'm winning. I have installed a second 6" vent on the north side of the crawlspace, and another 6" vent on the south side, allowing for adequate air flow of fresh air. The smell is almost gone. The crawl space is fully finished with concrete floors and walls, no exposed dirt anywhere. The baking soda is a great suggestion. I'll have to try it right away and see if it will eat up any remaining odours. I checked all around for the black mildew patches and found nothing. So the battle continues. Thank you again for your suggestions and time to reply.