The answer to 'dryer vent grimy' is that a grimy dryer vent is a common problem caused by lint buildup, which can be a fire hazard and reduce the efficiency of your dryer. Symptoms include longer drying times, increased energy usage, and visible lint or debris around the vent.
To address a grimy dryer vent, you should first try cleaning it yourself by disconnecting the vent from the dryer, using a dryer vent brush or vacuum hose attachment to remove lint, and then reattaching the vent. However, if the vent is severely clogged or you are unable to fully clean it, it's best to call a professional HVAC or dryer vent cleaning service to ensure it is properly cleared.