Nitrogen dioxide (NO₂) in outdoor air
Learn why NO₂ varies near roads, how it relates to fuel combustion and which station readings are comparable.
Why the station setting matters
Nitrogen dioxide is one of the gases grouped as nitrogen oxides, or NOₓ. Fuel combustion in vehicles, machinery and power generation is a major source. Outdoor NO₂ can vary over short distances around busy roads, so a traffic station and a background station can describe different conditions at the same time.
Check the station type before using one reading to describe a wider city. A regional grid forecast smooths variation within the model cell, including the difference between a main road and surrounding streets.
NO₂, particles and ozone
Nitrogen oxides take part in atmospheric reactions that can produce ozone and particulate matter. Their concentrations can therefore change in different ways over a day and across a region. An hourly NO₂ index band describes the NO₂ concentration for that hour, while ozone and particles retain their own bands.