Air pollution is an increasing problem around the world but some worrying new data suggests it might infiltrate our houses as well. In fact, as many as a quarter of Brits may be breathing in polluted air inside their own homes. That’s the message coming from Netatmo, a smart home company that analysed data from one of its products – the Netatmo Weather Station – in homes around the country. The company said that 23% of homes in the UK on average exceed the threshold of 1,000 particles per million (ppm) of CO2 at least once a day, meaning these homes aren’t ventilated well enough to evacuate pollutants. Apparently, we’re supposed to ‘air’ our homes at least twice a day to keep the oxygen fresh. The data says that 80% of Brits aren’t doing that.