dryer vent pipes

Do any of you put verbage to have a dryer vent pipe professionally cleaned? Seems like a good CYA in every report with a long pipe run since we can’t look inside them. I get some with lint built up so bad it is coming off the pipe as it travels through the attic.

I add this comment: Annual inspection and cleaning advised.

I also provide this link. http://www.cpsc.gov/cpscpub/pubs/5022.html

Exactly what I needed. Thanks David.

That link says corrugated semi-rigid duct is OK.

From CSIA: Clothes Dryer Venting Safety

“When a certified technician inspects and cleans a dryer vent, they also verify that the correct type of duct is in use. For example, plastic transition ducts (joining the dyer to the wall) should be replaced with metal duct, because it is non-flammable, unlike plastic.”