Installed in a home or office window, the “PuriFresh” heat recovery ventilator heats and filters outside air. The system is for people with respiratory illness (such as asthma, allergies, or emphysema) and for year-round indoor air quality improvement because it provides purified air that closely matches the indoor air temperature, says the company. Four HEPA filters clean incoming air and function as a heat exchanger. The system provides comfortable, fresh air without the use of an additional heating element.

ElasTek, Inc., 2 Chippewa Ct., Madison, WI 53711; 608-238-6466; 608-238-0270 (fax); (e-mail); (Web site).