Questions to ask before appointing a duct cleaning contractor

About the scope

• Which specific assets and duct runs are included, and which are excluded?
• Does the price include access panel installation where none exists, or will that be a variation?
• Are AHU internals, fans, attenuators and terminals included, or ductwork only?
• What happens if the survey finds contamination worse than expected?

About the method

• What cleaning method will be used, and why is it suited to this system type?
• How will the rest of the building be protected from dislodged debris?
• How is the work sequenced around occupancy, trading or production?

About verification and evidence

• How will post-clean condition be verified — measured, or judged visually?
• Will I receive pre and post clean photographs indexed to asset references?
• How will areas that could not be accessed be recorded?
• How soon after completion is the report issued, and in what format?

About the contractor

• Are the engineers directly employed or subcontracted?
• What association membership, insurance and competence evidence can you provide?
• Can I see an example report from a comparable building?

Reading the answers

Good answers are specific and unembarrassed about limitations. A contractor who tells you which sections they cannot reach and prices the access to fix it is being more useful than one who promises a complete clean of a system nobody has looked inside yet.

The single most revealing request is the example report. A strong contractor will send one immediately; a weak one will explain why they cannot.