You crawlers would have a hay-day in St. Louis. I don't think there is one hotel downtown that has ever had the duct cleaned. Their philosophy "If it hasn't been done in 25 years, what good is it gonna do now?"
Hotels can be wierd about their maintenance......$300.00-400.00+ per night to stay there but when you go out and inspect the ducts they are rarely if ever thoroughly cleaned.
This has been my experience here in LA. 9 out of 10 of them are either not being cleaned at all or are just being cleaned superficially.
Here is one from a very prominent hotel in downtown LA.....several movies have been filmed there.