Connecting the aroma diffuser to your HVAC thermostat for automatic control is possible and should be done by a licensed professional only. In principle, this approach entails having a power relay switch (sold separately in Home Depot and electronic stores) being triggered by the thermostat and on/off cycle the 110V source of the aroma diffuser.
Leveraging the thermostat control for On/Off cycles ensures 100% synchronization between your HVAC and aroma diffuser and negates the need to have the air handler fan On all the time. Some companies have attempted to use the pressure switch approach, but based on our observations thermostat connection control has superior accuracy. The pressure switch approach is prone to false-positive/negative as precise pressure calibration in the air ducts is often not possible.