According to the WHO, the indoor air is 10 to 30 times more contaminated with pollutants than the outdoor air.
Since people now spend around 90% of their time indoors, the effects are immense:
The first signs of poisoning are disturbances of well-being such as headaches and fatigue. Later consequences can be allergies and asthma, diabetes and cancer.
Science speaks of the "Toxic Home Effect" or "Sick Building Syndrome".