1. Good ventilation
Open windows from time to time to allow fresh air to move into the room. Otherwise, Carbon Dioxide (CO2) can quickly accumulate in a closed room and causes health problems.
If you are in a car, change the ventilation mode of the car to allow the outside air in from time to time.
Especially rooms where multiple people gather in for long time, e.g., Conference Room, can have very bad air quality. In such rooms, good ventilation is a MUST!