The key to healthy living is the atmosphere in the room. The main criteria here are its CO₂ content, relative humidity and temperature.
Ideally the relative humidity should be between 40 and 60%. Admonter natural wood products are also designed to be kept in such conditions.
In winter, however, heating can have the effect of reducing the humidity to below the bottom end of this range. In additional to regular ventilation, house plants and air humidifiers, it is also extremely useful to check the humidity using a hygrometer.