The air duct cleaning process begins with setting up the job, bringing in the HEPA-filtered equipment and protecting the floors and furniture with drop cloths. The HVAC system will be accessed through registers and access holes, starting from the furthest point on the supply side, agitating the debris toward the main trunk line. Then the same goes on the return side, usually the dirtiest side of the system. Lastly, the air handler, blower and indoor coil are cleaned and new filters are installed before the HVAC system is powered back on.