The furnace

Things to look for when a serviceman cleans your furnace.If the serviceman has no compressor your not getting professional service.
Is he certified?
Check list of a clean furnace.
1. Remove and wash the burners in warm water.
2. Remove and clean the flame rod,make sure the serviceman uses a carbon needle file.
3.Remove and clean spark ignitor rod with carbon needle file.Set gap to .225 thousands of an inch
4. Remove and brush blower and motor,the serviceman should clean the blower outdoors with an air compressor or nitrogen.
5. If furnace is a hot surface igntion system,the ignitor should be free of cracks and residue.
6. Remove flue pipe (mid efficient) clean inducer blower wheel with compressed air and vacuum at same time.The tube to the inducer motor pressure switch should be cleared of any ash.
7. Re-install all devices
8. Check functions and amperage of motors.
9. Motors drawing more current then rated, install dense air filter,balance supply air.
10.Check functions for 5 minutes minium.

These steps are for a clean furnace and is one hour of work.
There maybe more steps required  and are additional charged time for ,temperature rise and clocking the gas valve.