From a member of the ShanghaiMamas online community
I have read that we should open our windows daily to ventilate, but this leaves me wondering: Do the A/C wall units that we use for heating and cooling or true central air/heat systems (with ductwork) bring in air from outside?
The vast majority of wall-mounted A/C units and residential “central” air conditioners don’t bring in fresh air. They just recirculate indoor air. That hose that goes to the outside? It brings in liquid coolant, not air.
That’s why it is so important to ventilate regularly. Otherwise, you block out the particulates, but inside, carbon dioxide from breathing, and chemical emissions offgassing from paint, chemicals, cleaning products, and building materials all build up in the closed home or office environment. Opening the windows for only about 15-20 minutes will dilute everything.
Once you’ve ventilated, you need to turn on your air filters. This will cycle and clean the dust out of the air.