NOx Emissions

Until zero tailpipe emissions vehicles are being used at scale, we need to choose the cleanest technology available to reduce urban NOx emissions.

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What is NOx ?

NOx refers to both nitric oxide (NO) and nitrogen dioxide (NO2). These gases are released from vehicle engines and in cities and urban areas can reach harmful levels. They are an irritant and can cause inflammation of the airways.

Why is NOx dangerous?

NOx is an irritant. It mostly affects our respiratory system through potentially lethal inflammation and decreased function.

In the UK a nine-year-old girl’s fatal asthma attack has been linked to illegally high levels of air pollution. Ella Kissi-Debrah lived 25m (80ft) from London’s South Circular Road – a notorious pollution “hotspot”. She experienced three years of seizures and hospital stays before her death in February 2013. During that time, local air pollution levels breached EU legal limits. No individual death has previously been directly linked to air pollution.

    • What are the causes of NOx emissions?

    NOx is produced by combustion. This can be caused by engines, gas boilers, energy production and more. However, in urban areas where we see the highest levels of NOx, vehicle engines and traffic emissions are the main cause.

    In London, 48.9% of NOx comes from road transport while just 13% is from domestic sources according to analysis from Breathe London.

    See our NOx test methods and results

    • How to reduce NOx emissions

    The most effective way to reduce urban NOx emissions is to choose and use vehicles with the best AIR Index ratings, where ‘A’ is the cleanest. In fact, ‘E’ rated vehicles can produce more than 20 times the level of NOx emissions than an ‘A’ rated vehicle and so your vehicle choice will make a real and lasting difference to the quality of air that we breathe.

    You can search the ratings using our vehicle checker and please encourage family and friends to do the same because vehicles stay in use for a long time (up to 14 years, and sometimes for longer), which means the wrong choice can have a serious impact, years after the first owner has sold it.

    Best NOx emissions

    AIR Index

    Check the NOx emissions of your car or van

    The AIR Index rates vehicles tested in urban conditions which provides comparable NOx emissions levels
    that more accurately reflect the contribution to urban air quality than lab-based tests.

    Check your car now