£10 charcoal air filters can reduce Nitrogen Dioxide inside cars by 90%

Research conducted by the West Midlands Air Quality Improvement Programme at the University of Birmingham has shown that charcoal air filters in the £10-£20 price range are extremely effective at protecting car occupants from NO2 emissions.

Air filters that are currently fitted in cars primarily exist to filter pollen and have little or no effect on nitrogen dioxide, which is obviously present in high quantities in traffic.

The research tested the air quality in ten cars of differing sizes and engine types, under a variety of ventilation conditions: air conditioning on and off, windows closed and slightly open. Each vehicle was tested three times, firstly with its original air filter in place, then with a pollen filter, and lastly with the activated charcoal filter.

It was found that NO₂ concentrations were on average 1.6 times lower when the windows were closed the air was recirculated.  The pollen filters had no effect on NO₂ levels when fresh air was allowed into the car through the ventilation system, with levels the same as with the window open.

When activated carbon filters were added  NO₂ levels were on average 14.3 times lower with closed windows and recirculated air and with fresh air coming through the ventilation system, NO₂ levels were 6.6 times lower than levels with windows open.

Lead researcher Dr Vasileios Matthaios said: ‘Our findings show clearly that there are benefits to switching to activated carbon air filters, reducing exposure to NO₂ and the risk of related adverse health effects. These filters are simple, effective and inexpensive and should be considered, particularly for people who spend long periods of time in vehicles such as professional drivers.’

Professor William Bloss, co-author on the paper, said: ‘These results show a fairly simple way to improve air quality inside vehicles, although as the main source of NO₂ is our cities is diesel vehicles, reducing traffic emissions overall will bring the greatest air quality benefit across the general population.’