vac line help

[philsxt]

I noticed this vac line unhooked and wondering if someone can help me identify what it is and how its routed. Im guessing its for my hvac controls because they don't change and stuck on vent.http://i104.photobucket.com/albums/m193/phils94850/0jpg30_zpse415ce12.jpg (http://s104.photobucket.com/user/phils94850/media/0jpg30_zpse415ce12.jpg.html)

[shadow88]

I can't tell where that hose is, but the vacuum source for the hvac system is a nipple on the check valve on the brake booster for most cars.