attic fire has left smoke smell in duct work - How to clean?

[johnsonj]

I just replaced an AC for some folks that had a kitchen/attic fire in the past. They mentioned that there was always a light smell of "burning house" coming from the duct work. Now that we have dropped in the new AC, they are complaining that the smoke smell is 10X worse.

I was over there today, and they are correct. When I replaced the AC there was some mild smoke/heat dmg on the plenum, but everything else was in more than reasonable shape (unit was from 1987).

Since we don't do duct cleaning (and the house is two stories w/ inwall ducting, so replacing it would be $$), I need to send them off to the local competition.

Anyone have some advice I should offer them in terms of:
-type/method of cleaning they need?
-Chemical do/don't?

[drk]

Yes they need to have it cleaned! Any liner needs to be coated with something like Foster 40-20. Company needs to use negative air not a shop Vac are roto brush. Average size system two guys 5 7 hours to do. If they say they will use soot spray run away. If they clean it it is not needed.

[burnerator]

I know it's big$$ but the insurance companies normally pay to replace the duct work and repairs to make absolutely sure there are no more problems and usually they spray the smoke damaged wood as well.