Performed PTU on (1) Tempstar Dual Fuel Package Unit. Customer expressed concerns with dust substance coming from supply vents. Inspected system and found heavy amounts of substance buildup throughout, and heavy buildup on blower fins to point of particles flaking off during runtime. Cleaned system thoroughly and installed PlasmaPure whole house air purifier, along with UV light system. Duct system is in fair shape no holes or disconnected lines. Recommend cleaning supply registers of any buildup inside to help with issues as well, and considering duct cleaning or replacement if challenge persists. Invested in PSA (1) system using 1st visit today. Upstairs unit is not used as much only downstairs is under maintenance plan at this time.