I carried a KeepAlert CO2 Monitor on the train into the city today and the results were bad.

CO2 levels above 1,000 indicate an excessive build-up of CO2. At these levels people may start to feel fatigued or have a headache.

So the level on the train? 1,200.

This is a train returning into the city at the end of the day. It has just taken a load of people out of the city and is returning back in.

And the levels are still excessively high. So in a future test I will be seeing what they are like on the way out in peak hour.

Also keep in mind that CO2 is not the only issue. It is a great indicator that other things are building up as well. It indicates how much air we have breathed out is being recirculated. So it contains all the other by-products of our breathing, including our germs.

And for trains, there are all the train related by-products (you know the smells that I mean) that are being recirculated.

The solution is simple – get more fresh air in. But then that drops the temperature of the train which then means more heating. Or cooling in summer. And with winter fast approaching, shutting all those small windows is very, very tempting.

So do we need to be thinking further outside the box. How about a total flush of air at the start of the journey? Is it possible to ensure that we at least start with a cabin of fresh air?

And increase the amount of fresh air that is being fed into the heater / air-conditioner so that we don’t have to rely on blasting cold air in through the windows.

The benefits?

We will arrive at our destination less fatigued and without a head ache.

And I suspect that we will have decreased spread of illnesses because we have more fresh air and less recirculated rubbish.