The first phase of the Hampstead Neighbourhood Forum’s air-quality survey is now in its final month.

For the last 12 months, diffusion tubes have been positioned around Hampstead, collecting nitrogen dioxide (NO₂) for laboratory analysis.

Ten sites were selected from the 30 we measured in 2015. The lab calculates for each month a corresponding annual mean level – what the level would be if that month’s pollution lasted all year. We collect the last samples this month.

We have done better than before.

In 2015 we posted single diffusion tubes at 30 locations for six weeks, which gave us a useful picture of the area and informed the policies that were included in the Hampstead Neighbourhood Plan. This time, advised by Camden’s air-quality officer Tom Parkes, we used triple tubes over 12 months. Our data are the same "reference" quality as Camden’s.

Ham & High: Stephen Taylor says the current air quality testing is better than the one taken in 2015Stephen Taylor says the current air quality testing is better than the one taken in 2015 (Image: Miki Yamanouchi)

Our report this autumn will show monthly NO₂ at the 10 sites. Mostly, the air has improved since 2015. Monthly readings reflect seasonal changes: for example, domestic heating pollutes more in the winter. Those of us who notice fresher air in school holidays will expect to see that reflected in the summer levels.

But readings over a whole month mask enormous variations. In 2015, when we saw NO₂ annual levels were 75% above the legal limit at the top of Arkwright Road, we wondered how high they were during school hours. What is going into young lungs?

Our next goal is to answer that by studying the levels of (even more poisonous) particulates, especially around schools. With the help of our project co-leader, Katharina Schauer, a data engineer, this work will help the community understand how much the notorious Hampstead school run contributes.

Residents gave generously to fund the £2,000 cost of the first phase of our project. Volunteers, including children from three schools, went out in all weathers to maintain diffusion tubes. What we can do next depends again on the community’s generosity.

We hope to negotiate access to data from a network of more than 200 sensors installed round Camden this summer – see pollution in real time at airscape.ai. You can donate at hampsteadforum.org.

Stephen Taylor is vice-chair of the Hampstead Neighbourhood Forum.