Positive Input Ventilation (PIV) is a mechanical ventilation system that works by bringing fresh, filtered air into your home via ducting. Often just the one vent on your landing.
One of the main benefits of PIV systems is that they improve indoor air quality. By constantly pumping fresh, filtered air in to your home from outside, your air quality will be much better. The fresh air will help to reduce the concentration of pollutants and allergens in the air, making it easier to breathe which is great if you have asthma!