Originally Posted by
compressor stall
From Airbus yesterday:
Open nozzles will not provide a protective cone of air around the passenger and may assist in blowing the particles about the cabin.
They are doing further studies on airflow.
I was listening to the 1600 hr UTC webinar - the nozzles interrupt the vertical airflow that the maximum cabin air exchange rate is based upon. Similarly, so too does opening of the flight deck windows - it introduce a longitudinal cabin airflow they want to avoid as that too interrupts the cabin air exchange rate.