Condition before cleaning
Look for tears, erosion, delamination, wet spots, staining, and odor. A clean appearance is not the only acceptance criterion.
Material reading 22
Wet or moldy fiberglass may not be cleanable
Review condition before cleaning, then connect the observation to its source, system location, and a written scope.
DIRECT ANSWER
Start with the condition, not the sales package
Fiberglass duct board and internally lined sheet metal use porous material for insulation and sound control. EPA says wet or visibly moldy fiberglass duct material should be removed and replaced by a qualified contractor because cleaning is not sufficient to prevent regrowth.
Dry intact fiberglass needs gentle handling. Stiff brushes, high abrasion, or excessive moisture can damage fibers and facings. Ask the inspector to distinguish a surface dust concern from wet, deteriorated, or biologically contaminated material.
READ THE AIR PATH
What deserves a closer look
Moisture cause
Condensation, leaks, drain problems, and humidifier faults should be corrected before material decisions are finalized.
No casual coating
An internal sealant should not be used to hide damaged or contaminated porous material without a defensible product, use, and system plan.
USE THIS SEQUENCE
Move from observation to a written decision
Identify the material
Ask whether the duct is board, internally lined metal, or insulated flex.
Document damage and moisture
Require wider photos and the source location.
Choose qualified evaluation
Replacement can involve HVAC construction rather than cleaning alone.
Protect occupied air
Avoid methods that can release fibers or add moisture to porous surfaces.
CALL PATH
Ask about the evidence and the written scope
Sunnyvale Airflow Guide is an independent lead-generation website, not an air duct cleaning company. Calls may connect you with an independent service provider. Service availability, qualifications, pricing, and terms must be confirmed directly with that provider.