I read somewhere that Belfast is the most car reliant city in the whole of the UK.   Certainly, between all the diesel cars and the numerous busses spewing fumes, the air in Belfast stinks.   O n the government air quality site ( https://www.airqualityni.co.uk/current-levels/24 ), nitrogen dioxide levels in Belfast are currently 77 µgm -3. , this being only level 2 on a 10 point scale despite being almost twice the EU permitted maximum 0f 40 µgm -3 .   After commuting in or out of the city, I can often physically taste the fumes! This is one of the few things that I really dislike about commuting by bike, but then again, walking, driving or using public transport in the city still exposes everyone to these pollutants.   Some time ago, I had bought a few masks as above but there was insufficient space to fit them into my full face helmet.   And so, recently, I bought a flip front helmet.   With this, I can put the mask on before lowering the...