Classroom carbon dioxide levels up to three times above watchdog guidelines

Some school leaders say CO2 monitors provided by DfE are having no impact

Some school leaders say CO2 monitors provided by DfE are having no impact


Classroom carbon dioxide levels are up to three times higher than those recommended by the health and safety watchdog – despite schools following government guidance to increase ventilation.

Some school leaders say the CO2 monitors provided through the Department for Education’s £25 million ventilation scheme are having no impact as, once a problem is identified, the advice to open a window does not always work.

Such high levels are not safe if a person with Covid is in the room as the virus is “much more likely to transmit at those levels”, one expert said.

‘What am I supposed to do?’

It is expected the 300,000 promised monitors have now been delivered to schools.

Guidance states a consistent CO2 concentration of more than 1,500 parts per million (ppm) “is an indicator of poor ventilation”.

Less than 800ppm implies a space is well ventilated. The Health and Safety Executive (HSE) also recommends rooms are kept below 800ppm.

Vicky Rogers, a year 6 teacher in Hertfordshire, said the CO2 monitor in her classroom regularly showed more than 1,500ppm, despite open windows and doors.

The monitor registered 2,798ppm at its peak – when pupils were discussing work – even though a third of the class was absent with Covid.

The Department for Education advises schools “take action to improve ventilation” when readings are above 1,500, but “there is no need to stop using the room”.

Operational guidance for schools advises opening windows and internal doors to improve natural ventilation, or to make use of mechanical ventilation systems.

“I’ve got my doors and window open, so what am I supposed to do when it tells me [CO2] levels are poor?,” Rogers said.

‘Most of them are off now’

A primary head from Wolverhampton, who wished to remain anonymous, admitted “most” of the CO2 monitors in their school were turned off after they registered levels above 1,500.

One classroom recorded 1,669ppm, despite temperatures dropping to 5C because of open windows and doors (see image).

The head now closes windows because it left pupils “freezing and miserable”. HSE recommends minimum workplace temperatures of 16C.

The DfE says schools should “balance the need for increased ventilation while maintaining a comfortable temperature”.

A school business manager from a large secondary in Surrey is forecasting “at least a £40,000 increase in energy costs” because of heat escaping through open windows.

The Wolverhampton head said the monitors were a “great gimmick”, but “in terms of impact, they’re nothing. All they do is tell you to do something that you’re already doing.”

Schools Week spoke to staff at five schools who had recorded at least “poor” CO2 levels. Many more have also posted high readings on social media.

Dr Deepti Gurdasani, an epidemiologist at Queen Mary, University of London, warned the 1,500 threshold was “not safe. If there is a person with Covid in the room it’s much more likely to transmit at those levels.”

Recent Office for National Statistics figures suggest about one in 28 school age children currently has Covid.

‘Next logical step is to filter the air’

But Dr Matt Butler, from the Fresh Air NHS campaign group set up to improve ventilation, said high CO2 did not mean high risk of Covid.

“What it means is you’re breathing in a lot of other people’s air, so what you then need to do is either reduce the CO2 or filter the air.”

A Teacher Tapp survey found just 10 per cent of secondary school classrooms are air-conditioned, falling to 7 per cent in primaries.

Butler said the “next logical step” was the use of HEPA (high efficiency participate air) filters that clean the air.

The government last week pledged 1,000 air cleaning units for alternative provision and SEND settings, although no date was given for the roll-out.

Mainstream schools will have to purchase devices through an online “marketplace” from December. Geoff Barton, the general secretary of the Association of Schools and College Leaders (ASCL), said units “should be funded for all schools”.

A £1.75 million government-funded school trial to test the feasibility and effectiveness of the filters and ultraviolet lights to stop the spread of Covid was announced in August.

Professor Mark Mon-Williams, who is leading the project, said while filters were “relatively straightforward to place in schools”, UV devices involved “making building alterations”.

“I expect to have a picture on the effectiveness of the devices during the first half of next year,” he said.

A DfE spokesperson said schools are “generally finding the monitors to be a helpful tool to manage ventilation”.

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