My wife and I have a summertime condo down south.
The beach house sits locked up tight for weeks before the people I was with and I get down to it.
The first week the people I was with and I are back is always the worst week of our trip. The beach house is always a total mess. The surfaces are all dusty and there are dead bugs everywhere. The toilets and shower all get moldy due to the water sitting stationary. The HVAC component also needs some work. The air filter should be changed due to the dust and stale air. The inside of the heating and cooling component could use some cleaning too. You never think what has crawled and died inside of the HVAC. The worst is checking out the ductwork attached. The outdoor vent is in the garden. There could be dirt, leaves or dead pets in the outside vent. Then if the people I was with and I turn on the HVAC, the air blows over that debris and pollutes the air quality. It is always a frightening moment checking the vent to see what got into the ductworks. My wife and I take turns looking inside of it. The best is when it is a little bit of dirt. Every one of us just stick a long pole with a towel attached to it through the ductworks. The worst was when a squirrel got into the ductwork and died. Every one of us got a professional ductwork cleaning corporation into the beach house to take care of that one. It was super stinky and gross. Now the many of us forever worry about it happening again.