It is the responsibility of the Installer to identify when asbestos is present on the work site but HERS Raters should always visually verify the fittings and insulation on older duct systems before testing. For more information HERS Raters should read, A Consumer’s Guide to Asbestos which is available from the CSLB (Contractor's State License Board:) . If the installer certifies on the CF2R-MCH-01 that the duct system is sealed and/or insulated with asbestos products, that duct system will be exempt from duct testing. It is the responsibility of the local building inspector to confirm that claiming this exception is justified.