Keep an eye on humidity
Another reason to ventilate is to counteract humidity in regions where this can be a problem. Those of us in coastal dwellings are all too aware of the issues caused by high humidity, when there is a lot of moisture in the air that comes off the sea or another water mass. In summer months or warm climates, the air is able to hold more moisture, hence the sticky feeling that can accompany hot weather. Not only can this be uncomfortable for your baby and disrupt sleep, humid air can produce mould, which carries all sorts of harmful bacteria and can cause or exacerbate asthma. Remember that babies are more susceptible to all of this due to underdeveloped immune systems.
While air circulation is, again, important to prevent mould spores settling, be aware that opening a window will not work in cases where the outside humidity is higher than that inside. Coastal or tropical climates are prime candidates for this issue, for example the north and north-eastern coasts of Australia and much of southeast Asia. In this case, good insulation combined with air conditioning is necessary instead. Alternatively, a plug-in dehumidifier can be used if you don’t have air-con, and the hanging of any wet washing should be done far away from baby’s room, preferably outdoors.