CO2 Monitor Checks for Poor Ventilation

Back in 2021, I borrowed a Carbon Dioxide (CO2) monitor and found out that the air in our bedroom becomes unhealthy if we shut the door overnight (see graph below). CO2 that we breathed out accumulated due to poor ventilation, because our bedroom sash windows are sealed with secondary glazing in winter to make them more energy efficient.  We’re planning to have them refurbished soon, with double-glazing or vacuum panels, which will save energy AND let us control the ventilation better.   

Insufficient ventilation like this can be bad for your health, causing drowsiness and discomfort and making it hard to concentrate with more serious effects at high concentrations. It can cause high humidity too, risking condensation and mould, another health issue. It also increases the risk of airborne cross-infection between people in the room, so CO2 monitors were used in schools, etc during Covid, to signal the need for better ventilation or less crowding when CO2 levels rose.

If a room’s CO2 rises above 1200 parts-per-million (ppm),  that progressively needs more action to improve ventilation for the reasons above.

On the other hand, too much ventilation from draughts or open windows can waste heat in winter, resulting in higher energy bills and carbon emissions. It’s indicated by a rapid fall in CO2 when people leave a room with its internal door closed.

Checking your home with a CO2 monitor can help you get each main room’s ventilation balance about right.

The steady rise of 420 ppm CO2 in outdoor air is a massive threat to us all, as it’s the main cause of climate change! The CO2 Monitor’s instructions say that it’s 400 ppm, which was true a decade ago!  Fixing this needs humans to rapidly phase out burning fossil fuels – a bigger subject!  

You can find out which of your rooms, if any, have too little (or too much) ventilation by booking a Carbon Dioxide Monitor loan for free from Cambridge Carbon Footprint, like we did. It displays CO2 levels and can record  them every hour. When you connect it via USB to your laptop, it appears as an external drive, like a memory stick, and you can save the recorded readings, as in the graph, plotted with Excel. They are on loan, normally from Friday pm to the next Friday am. from volunteer hosts in Cambourne, Histon and Chesterton.