Has the services supplier adequately demonstrated that duct do the job and plenums are cleanse? (Plenum is a space by which provide or return air is blended or moves; might be duct, joist Room, attic and crawl Areas, or wall cavity.) Your technician shouldn't spray any chemical cleaning products as https://air-duct-cleaning43219.salesmanwiki.com/9028948/top_air_duct_cleaning_secrets