No, ventilation is not enough.
Ventilation is used by promoting indoor air circulation, letting outdoor air come in, with the intention of air renovation.
There are several ways to indoor air renovation, from the simplest window openings, up to the complex air conditioning units for big buildings. To understand how effective they are, let us introduce the ACH (Air Changes per Hour) concept. If for a room, we are able to renovate the whole air volume in an hour, we will say that effectiveness is 1 ACH. If in the same room we get whole air volume renovation 5 times in an hour, effectiveness is 5 ACH.
Air Conditioning Systems for Hospital Isolation Rooms, or Intensive Care Units, are designed to achieve at least 12 ACH. Just one LIGHTDIS Upper Room fixture provides an equivalent effect of 15 to 20 ACH, sterilizing the air with people present in room. Opening windows rarely reaches 2 ACH.
Air room renovation happens, because when we open the window, outside air enters in the room being mixed with the air inside of the room. Same as indoor and outdoor air get mix, infectious agents, virus and bacteria present in the indoor air, are mixed with the new air coming from the outdoor. So even renewing the whole air room volume, we will keep microorganism inside de room. Studies show that in real conditions, and using very powerful air conditioning machines, only the 20% to 60% of existing indoor air microorganisms are expulsed outside (1). Expulsing a 20% or a 60% depends of air stream, and streams able to remove a 40%, normally are very uncomfortable for people. By the other hand, windows can’t be opened all the time (cold, warm, rain, snow….). Anyway, while infected persons remain indoors, always there will be infectious agents in air. So, increasing ACH helps to control viral load in the air, but only up to a limit. Actually ventilation reduces viral and bacterial load in indoor air, but it’s not enough to get rid of pathogens.
- American Conference of Governmental Industrial Hygienists. Industrial ventilation: a manual of recommended practice. 24th Cincinnati: ACGIH;2001.
