Airtrim is a heat/moisture exchanger which recovers the heat and moisture from exhaled air. The filter heats the air you breathe in, protecting your air passages from the cold.
There are many different filter types - Sport, Asthma and Race I, II, III. The Asthma filter gives the most warming (lowest airflow), the sport is designed for low- to medium-intensity training, and the race filters for high-intensity workouts.
During continuous use the filter gets very damp, and you should clear it regularly by blowing vigorously through the mask. Avoid touching the wet filter as it tears easily. Allow the mask and filter to air dry. Always bring along spare filters on long training sessions and mountain trips. Spare filters must be kept dry. Filters that are adequately dried between uses should last 20-30+ sessions.
Asthma filter for people with asthma or angina who suffer from the cold sold separately. Because it
conserves heat more effectively, it can be used to ward off hypothermia
in the event of an accident.