Constant ventilation is essential if you want to maximize the quality of indoor life and achieve a healthy environment. After all, you spend about 85% of your time indoors. Ventilation helps prevent unpleasant smells, allergies, and other health problems. Furthermore, the building or house will be protected against condensation and mold problems. Air must circulate from dry to wet areas, in dry areas fresh air must be supplied, and in wet areas contaminated air must be removed. The implementation of ventilation and extraction systems is subjected to a long list of requirements and rules that can be found in the CTE, HS3.