sweet smell is coming out of the registers

In a heating cycle I noticed a strong sweet smell coming out of the registers but not in every air change. It feels like the ozone gas but a little different.
(It’s a one and a half year old system with electrical furnace “carrier”, with pleated MERV7 filter)

Does anyone know what that smell could be, what could cause the issue and how to get rid of it.

Thanks much, Bo

By chance is there a electronic air filter or any other devices present ? Like a air purifier

Google ozone smell in registers and you will get quite a few responses.

no air purifier, brand new home and system about year & a half old. There are 2 furnaces on the second floor, one for downstairs and another for upstairs and both are releasing the sweet smell when in heating mode

Gas furnace with a heat pump by chance?

may have refrigerant leak by the heatexchanger . that would be very odd but possible