Choosing to breathe healthy air, because it is constantly replenished and purified, is essential. It is important for our health to breathe air that is clean, rich in oxygen and free of the pollutants that unfortunately accumulate and concentrate in closed, stuffy rooms. As confirmed by numerous studies, indoor air can be 5 to 20 times more polluted than outdoor air. Without proper ventilation, indoor air tends to deteriorate, becoming saturated with harmful substances that can be very dangerous to health. Harmful elements include ultra-fine dust, fumes, combustion gases, formaldehyde, volatile organic compounds released by chemical detergents, glues and furniture materials. Then there are pollutants of biological origin – microorganisms such as allergens, moulds, bacteria and viruses carried by aerosols – and those of physical origin such as the dreaded radon gas