For the first night of testing these, we placed them under a lip of the cat's bed and nothing really changed. However, for the second night, we placed the bed into a bigger box and this resulted in a somewhat fresher-than-normal kitty bed.
We do keep and change a towel, which spans the cat's bed. But, leaving charcoal at the scene of the crime seems to help the situation as well. These are really cool. There is probably about a hundred ways to effectively use them.
Vital Link: Amazon