I searched the POR-15 website, they really don't give much info. the only knowledge I have is from guys on THIS board. here is what I found at
http://www.por15store.com/dosdonts.html
"Do use an organic vapor particulate respirator, NIOSH/MSHA approved when spraying POR-15. If you are spraying in an enclosed area, you must use an air-supplied respirator"
"must" isin italics and bold on their website. does their disclaimer indicate if you're shooting in the driveway for example, you could wear an organic vapor respirator and achieve adequate protection?