Son just moved into a house that has gas, forced hot air heating (in New England) The ducts are also used for A/C system where the condenser is mounted outside the house.
Realize this is a pretty general question, but nobody in family has ever had this type of heating system before:
How often is it a "good idea" to hire a duct-cleaning company to come in and clean out all the duct work ?
Can't know for sure, but it wouldn't surprise me if it hasn't ever been done since the house was built 25 yrs ago.
BTW: how do they do this ?