Hello:

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 befo

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 ?

Thanks,
Bob