Dryer vents: whose lint is it anyway?

Clogged or disconnected dryer vents in a common laundry room are a fire risk and a moisture problem, and they land on the building side of the ledger. Disconnected flex duct behind a machine is the classic find. How often do your vents get cleaned, and is it on a calendar or on a complaint?

The disconnected flex duct behind the last machine in the row is practically a rite of passage — everybody finds it eventually, usually by the moisture stain or the lint blown across the laundry room wall. It is a fire risk and a drying-performance complaint rolled into one, and it lives in the gray zone between the laundry vendor's contract and your own crew's rounds. How often do your common-area dryer vents actually get cleaned — and whose job is it on your property?