A system includes an inlet to collect air from outside a building; an air filter coupled to the inlet; a baffle to receive air from the inlet; an actuator coupled to the baffle; one or more sensors exposed to air from the air filter to determine air quality; a controller coupled to the one or more sensors and the actuator, the controller closing the baffle if air quality is below a threshold; and an outlet positioned after the baffle to deliver air to the building.