WHO guidelines

The World Health Organisation (WHO) has designed clear guidelines on air pollution from fine dust (indoors and outdoors), indicating that presence with an aerodynamic diameter of 10 μm or smaller (PM10) is damaging to your health. These small particles are invisible to the naked eye and do not necessarily produce a noticeable odour. Therefore a visibly clean room can have a considerable air quality issue.

In the latest research  from the World Health Organization (WHO), it is reported that in 2012 around 7 million people died - one in eight of total global deaths - as a result of exposure to indoor and outdoor air pollution. This finding more than doubles previous estimates and confirms that air pollution is the world's largest single environmental health risk. Reducing air pollution could save millions of lives.