flea and a fly in a flue

Buckley Rumford Fireplaces
A flea and a fly in a flue

A flea and a fly in a flue
Were imprisoned, so what could they do?
Said the fly, "let us flee!"
"Let us fly!" said the flea.
So they flew through a flaw in the flue.
--Ogden Nash

I think, if one of those "chimscams" found a flaw in a flue, we could caution our customer about fixing it lest the house become full of flies and fleas.