Air Duct Cleaning. Some think it’s a scam. I doubt that, but I expect the need would depend on your home and your family. There’s no question dust and all sorts of nasty things get hung up in heat ducts and can dislodge and become airborne again. Is it worth it to get them cleaned? Probably. Especially if you have allergies.
Here’s a loosly related story about things getting hung up.
When I bought my house it was about 30 years old; a big 2-story; solid, well-built but really worn. Needed alot of work. It had been a foster home for years and it really showed the wear and tear.
One of the nice features I remember when we looked at this house was a laundry shoot; crucial really, especially for a two story with laundry facilities in the basement (two flights down from the bedrooms, where most of the laundry comes from and goes to). REALLY handy!
It was a good sized shoot. You could stick your whole head in and look around. Once in a while we’d catch the kids climbing in and dropping down into a pile of dirty clothes on the basement floor (Thankfully they never tried this from the 2nd floor).
When we first moved in I noticed something hanging in the shoot between floors. A rag or a piece of clothing or something got caught on nail or something protruding from the wall inside the shoot.
I got a broom handle and snagged it. It was a very large pair of women’s underpants. About the size that would’ve fit the previous owner. Presumable dirty, since it was hung up in the laundry shoot! EEEEEEW!
So, who knows what kind of treasures might be hanging around inside your air ducts!
Get a contractor to check it out occasionally! And while you’re at it, have your entire HVAC system cleaned and checked.