Begin with evidence
EPA does not recommend cleaning air ducts on a routine schedule. Ask an assessor to show the condition that justifies cleaning. Dust on a return register alone does not establish contamination throughout the system.
Ask what is included
Request a written list of the supply and return ducts, registers and other HVAC components included. Ask how accessible components will be inspected, how debris will be contained and what cannot be reached.
Address the cause
If contamination is identified, ask what caused it and what needs correcting. Cleaning alone may leave the underlying condition unresolved. Do not accept a health guarantee or an automatic claim that cleaning will reduce energy bills.