Basement air goes everywhere
In a lot of New Jersey homes the furnace or air handler sits in the basement, and so does the return side of the ductwork. Leaky return ducts, or a return grille in the basement itself, can pull basement air with its damp and its smells into the system and send it to every room upstairs. Sealing the returns and dealing with basement moisture often does more for the air than any gadget.
Humidity, both ways
Summer here is humid, and a house that sits above about 60 percent humidity invites mold and dust mites. A correctly sized air conditioner, or a dehumidifier in the basement, keeps that in check. Winter heat does the opposite and dries the air out, which is where a humidifier on the furnace can help.
Filters, cleaners and fresh air
Filtration is the simplest upgrade, and the maintenance guides cover sizes and schedules. Air cleaners and UV lights have their place, but each solves a specific problem, so know which problem you have before buying one. Homes sealed tight for efficiency, and households where someone now works from home all day, also benefit from a planned supply of fresh outdoor air.