SUNON Flow2 One-AHR Ventilation Fan is a single room air exchanger with heat recovery ventilator. keep interior climate at an optimal condition Flow2 One works like a mini heat recovery system with efficiency of 42% heat recovery, so it balances the interior temperature and moisture. Simple but elegant design The Flow2 One is compact in size, and can be installed in area with limited space. Small size and easy to installation Different with other ventilation fan that install is a big construction, the Flow2 One is a through-the-wall ventilation unit, and thus only small wall sleeve can install it easily. Caring design for its product (1) Hidden dust filters design The Flow2 One features the anti-PM2.5 particulate filter to prevent pollen, dust, insects entering from the outside. (2) Anti-rain protection Cowl Equipped with outer hood rain cover for protection against rain and insects. Extensive use in various locations Widely installation in house, school, hospital etc.