Natural Air 350 units offer efficient, balanced ventilation that produces healthy indoor air quality while saving energy with its efficient EC ball-bearing motor. Meanwhile, ultrafine G4 filters ensure a pollutant-free environment that's literally a breath of fresh air for allergy sufferers. You will also enjoy a comfortable temperature without annoying draughts or cold spots thanks to the unit's 100% summer bypass and winter defrost functions , so no matter what the weather's doing outside, everything will feel just right inside. NA350 is SAP Appendix Q listed.