My cat (full grown adult) has walked past the unit many many times without it going off. I have moved it, turned it, changed the position on the unit, and placed it on the floor in front the open bookcase I'm trying to protect. It never goes off. On the other hand the humans it the house set the darn thing off every time! Don't waist your money. I thought this was too expensinve with the belief that it would worked.