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You may have noticed these test tubes on lamp posts all over the UK recently. What do they do? And where did they come from?

They’re part of a clean air scheme and they’re used to collect samples of Nitrogen Dioxide or NO2 in the air by diffusion.

They are sent to a lab and analysed to see what levels of NO2 are in the air as part of the effort in your area to target high levels of pollution and make the air cleaner.

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