Yep it makes sense to me that the fragrance and fabric softener sheets could present a problem. Didn't even occur to me as we use free and clear detergent and use no fabric softeners. Even then, personally I would have no problem unless the plants are growing directly in the stream of air flow. I still think that some kind of barrier or deflector shield, maybe a foot from the foundation would be a good solution as it could deflect the exhaust to over and around the herbs. Lastly, in terms of any possible health risk. I'm wondering what volume of these plants do I eat and how much of this low level exhaust material is likely to get ingested. The answer is probably just above zero. For me, if I didn't have an alternate location, would plant the herbs, modify the air flow as much as possible, and let the taste test determine whether the herbs were suitable or not. From my perspective there is no valid reason to be overly anal about such low levels of fairly benign chemicals. After all, one grocery store bell pepper probably will have thousands of times more residue and of the highly toxic kind. Such simply can't be avoided, though we work hard to avoid the worst, often buying organic for the most serious pesticide offenders.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.