Ventilation is one of the basic requirements of a good house. As fresh air is a must to ensure the health of those who live in the house good ventilation is a must. In tropical climes it is not difficult to follow ventilation options when building a house. You can incorporate a lot of windows and they will provide the necessary ventilation with natural wind blowing. In countries where there are harsh winters it is not possible to have many windows in a house. Even if you do have you must close then and stay indoors during winter.
Now you are faced with a problem on how to ventilate your house. The best way is to expel some air from the areas where the air gets contaminated or become stale. Exhaust fans are most suitable way to expel the stale air from the house.
Kitchen is one of the places where the air gets polluted due to air being contaminated with cooking. If you are using a gas stove naturally some oxygen will be burnt. Unless you have a chimney from which the carbon dioxide is expelled into the out side of the house it will remain in the kitchen polluting the air. You must force this polluted air out with a window exhaust fan to allow fresh air to come into the house.
Your bathroom is the other place where the air will become damp and stale. Here too you must find a solution. The smells of soaps deodorants washing powers and everything else used in there will get mixed with air and the moisture from the evaporating water will make the walls damp. To solve this problem the best thing is to fix a window exhaust fan and make proper ventilation.
Once the ventilation is ensured in those places where the air gets contaminated your house will be a better place to live.