Show where you found the dust
Photograph the area only if it is visible through normal owner access. Do not remove electrical, burner, or blower service panels to gather more evidence. Tell the technician whether the dust was found during service, whether it is old or newly accumulating, and whether there has been recent construction or another dust source.
Save the filter brand, dimensions, rating, installation date, and any service recommendations. Note whether the filter sits loosely, appears damaged, or requires force to fit. Follow the equipment's owner instructions for approved replacement and access.
Ask for findings before buying an upgrade
Request inspection of the filter rack, fit, applicable seals, and the actual path air takes into the equipment. Ask the technician to explain where air can reach the area without passing through the intended filter and whether the observed material is meaningful to equipment operation.
If a different filter is proposed, ask for its compatibility and the measured effect on airflow. MERV is a particle-capture rating; a higher number alone does not establish a suitable replacement. PNNL discusses filter pressure drop and system compatibility in the same guidance.
Match cleaning to a verified need
Ask which component needs cleaning, why, and who performs that work. Request photographs and a defined scope rather than a broad promise to remove all household dust. If related duct inspection or work is needed, have the appropriate provider coordinate it with the equipment assessment.
Your next step is an HVAC service review of the visible dust, filter fit, and airflow. Resolve the actual route or equipment finding before using a denser filter to hide a problem that has not been identified.