I was highly skeptical, but we have 10 cats (yah, crazy, i know) - we just added 2 new ones to our 8 - and they wouldn't stop fighting. We put these in and life became peaceful! Holy Cow! I was shocked! They actually work!!! We plugged 3 into our first floor.... we have 4 rooms and a small bathroom - open concept - so we wanted to make sure we had enough with all the space. We can't smell anything and it hasn't set off my asthma.
I HIGHLY recommend it for anyone with grouchy kitties!!! We give it 10 paws up!