The air outdoors is crisp and pollen-free. But make sure the air indoors is just as clean. Warm up. A cozy night in front of a warm fireplace -- there’s nothing better. Just make sure you store firewood outside, to keep mold and pollen where it belongs. Clean heating ducts and filters. Dust and dust mites thrive in your heating system. Professional cleaners can give your ducts a clean bill of health. Change heat system filters at least once a month. Wash Fido and Fluffy. When it’s cold outside, pets need to come in. Just keep them in a confined living area. Also, give them a bath every week, if pet dander is a problem. Beware of extremes. When it’s very cold outside, keep your face covered. Going from very cold air to very warm indoor air can trigger an asthma attack if you’re not careful.