Good breath is conducted via nose, not via mouth. If we keep the mouth tightly closed, the breating will be carried out by the nose. Since long time ago, many people practiced cleansing nose. It is said, just as we wash our mouth every morning, the nose should also be cleaned. Clean water, cold or lukewarm, is the best agent for that purpose. It was taken in a cup or in the palm of the hand and drawn up through the nostrils. It is possible to draw the water up through one nostril, the other remaining closed, and expel it through the other by opening it and closing the former. The process was carried out gently so as to avoid discomfort. In order to cleanse the back portion of the nose known as nasopharynx, sometimes the water was brought out by mouth or even swallowed.
Naturally, we must see that the air that we breathe in is fresh. Ancient people said that it is good to cultivate the habit of sleeping in the open under the stars. The fear of catching a chill can be dismissed from the mind. Cold can be kept out by plenty of covering, where this covering does not extend beyond the neck. If cold is felt on the head, it can be covered with a separate piece of cloth. In the process, the opening of the respiratory passage – the nose –would never be covered up.
The day clothes were changed for loose night clothes before retiring. As a matter of fact, no clothes are necessary at night when one sleeps covered with a sheet. It is recommended by some cultures to avoid tight-fitting clothes even during the day.
The atmospheric air around us is not always pure, neither is it the same in every country. The choice of the country does not always lie in our hands but the choice of a suitable house in a suitable location does rest with us to some extent. The general rule is to live in location which is not too congested and ensure that the house being well-lighted and well-ventilated.
Source: Key to Health