I had a friend who's BP was sensitive to lavender oil (in incense a room away), any trace of dust in the substrate (no aspen), and just generally would act up with RI like symptoms to certain substances. Her other BP never showed the signs or ever had anything but a clean bill of health from the vet. I'd keep an eye on your BP, and find a different solution (keep him in a different room, turn off the dispenser, something that works for you) at any sign of wheezing, clicks, or other respiratory distress