Nose & scarf
That's great question! a scarf works best because it takes on warmth from your exhaled breath & transfers it to the incoming air. Breathe through your nose not your mouth.
The nose is designed to warm & moisten air; the mouth can't. Ipratropium
) is often used to help control cold weather-triggered asthma
. Make sure your asthma is under control before venturing out into the cold.