Air is all around us. Every day we breathe it in 20,000 times, which equals 10,000 litres of air per day. While awareness of outdoor air pollution is growing, we are still (too) often unaware of the quality of our indoor air. And this while we spend up to 90% of our time indoors, where the air quality is on average 5 times worse than outdoors. So why don't we think more about the air we breathe and what it contains?