The air we breathe

We’ve thought a lot about the air we breathe this year (especially about whether someone else breathed it first). Even without government prohibitions the risk of being in enclosed spaces with other people was obvious, so most of us have been happy to focus on outdoor activities.

The ringing room is an enclosed space, and ringing bells requires more effort than sitting in a pew, which is why we’ve been ringing handbells outside the west door since services resumed at Easter.

When the Government ‘Roadmap’ allowed limited indoor activity from 17 May, the guidance agreed with the Church of England for bellringers was also relaxed to allow tower bell ringing with appropriate precautions. As well as the usual (hands face, space) it included ‘maximum ventilation’, which is fine if you can open doors or windows to fresh air, but we can’t. We just have ‘natural leakage’ – though the leading in the west window and through the rope holes in the ceiling. So is our ‘maximum’ enough?

In our favour is the high ceiling, so regardless of external air the large volume dilutes what we breathed out, which slows the rising concentration of exhaled particles. But how slow? And how long is it safe to ring?

Fortunately there’s a way to measure the build up of breath in the air, because as well as breathing out aerosol particles that might carry the virus we also breath out carbon dioxide, and that can be measured. In fact it’s a standard way to test the effectiveness of building ventilation.

Understandably there is a high demand for CO2 sensors at the moment but we were able to borrow one to monitor the air while we are ringing. The day the rules changed to permit meeting indoors was our normal practice night so six of us (the maximum allowed) gathered for our first ‘normal’ ringing for for a very long time.

The CO2 level rose fairly quickly as expected, but when we ran the fan in the aircon unit it mixed what we had breathed with the unused air above, and kept the CO2 around the same level for the rest of the session.

We will do more tests and continue to monitor the air, refining how we operate, but we hope that semi-normal ringing will be possible from now.

John Harrison (June 2021)