FAQ41: Can Air-Conditioning Increase Mucus?
There are two things about air conditioning which can cause mucus to increase. One is that air conditioned air is drier than warmer air. Cool air cannot hold as much moisture. So do the things you know how to do to increase humidity such as use a humidifier, dampen foam or cloth stoma cover, wear an HME (Heat/Moisture Exchange) filter, use the saline bullets, etc.
An increase in mucus and coughing should also occur because the air is cooler. Your trachea and lungs like warm air (body temperature at the bottom of your lungs), and breathing cooler air will trigger the production of mucus. There is less that can be done with this other than don't keep the temperature so cool, and wear an HME which helps conserve the warmth in exhaled air in the filter until you inhale again. If you wear a foam cover, you can also increase the warmth of incoming air by also wearing a lined cloth cover over that.