Heavy breathing in cold temperatures or low humidity (desert climates or high altitude) can be uncomfortable or damaging to your airways. The AirTrim Mask is designed to recover heat and moisture from exhaled air - protecting your air passages from the cold and dry. This AirTrim Asthma mask offers the highest warming and moisture retention level of any AirTrim cold weather mask. It comes with two Asthma filters. This mask is perfect for those with exercise-induced asthma who still wish to participate in outdoor aerobic activities. Instead of wearing a buff or scarf over your face and nose, switch to a much more comfortable AirTrim mask. A study at the University of Montreal found that the AirTrim mask is excellent for training and low-exertion activity. They recommend using it for warming up and easy effort activities. Once you have a race or interval session, it is recommended to remove the mask to allow unrestricted oxygen flow. To read the whole article, head to this link: With our experience here at Skiwax.ca, we agree with this assessment of the AirTrim Mask. The mask is great for warm-ups, easy skis, and cool-downs, so removing the mask or having the Racing 2/3 filter for more strenuous efforts will make you feel and perform better.