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FactCheck: Does this Dublin video prove masks increase carbon dioxide to dangerous levels?

A protester in Dublin claims her carbon dioxide-measuring device proves masks cause CO2 levels to exceed ‘dangerous’ amounts.

A VIDEO OF an Irish protester claiming she can prove masks cause ‘dangerous’ levels of carbon dioxide for wearers has been disseminated across social media. 

In the video, which was taken on Merrion Street in Dublin outside the back gate of Leinster House, the woman inserts a carbon dioxide monitor into her mask and states that when the device detects a dangerous amount of the gas, an alarm will sound. 

She claims the CO2 reader was detecting levels of 480 parts per million in the air before she placed it inside her mask and that 400-700 parts per million is a healthy range. She says levels of over 700 parts per million can lead to headaches, drowsiness, anoxia (where the body or brain loses its entire oxygen supply), cerebral injury or comas, and that death can occur at levels over 5,000 parts per million. 

As she continues talking, with the monitor placed inside her mask, the counter on the device can be seen increasing from 419 to 1,895 in the space of 19 seconds causing the alarm to go off. 

She removes the device after it hits 10,000 roughly 50 seconds after inserting it into her mask. 

“Now this is dangerous and how long did I have my mask on?” she says to a small crowd of people around her. “The government is asking our children to wear masks for six to eight hours a day,” she says, appearing to take aim at the recent recommendation that children in third class and upwards should wear masks while at school.

The clip was shared on Facebook by at least seven separate pages and groups with one video clocking up over 6,500 views . It was also spotted on Twitter. 

Screenshot 2021-12-16 at 18.35.41 Facebook post with video gets over 6.5k views Facebook Facebook

A reader sent it to The Journal with a request to verify the claims after they were sent it on WhatsApp. 

Given the heightened debate around masks following the recent mask requirements in schools, we decided to check the video out. 

The Claim

That a ‘professional carbon dioxide detector’ proves masks can increase carbon dioxide to a level that is dangerous to human health. 

The Evidence 

Carbon dioxide is found in the air and is typically harmless to humans, but at high concentrations can be dangerous. The UK’s Health and Safety Executive notes that rising concentrations of CO2 can indeed, as the video claims, cause headaches, dizziness, confusion and loss of consciousness, and says that exposure should be limited to a maximum of 15,000 parts per million over 15 minutes. So can masks lead to this kind of exposure to carbon dioxide? 

University of California Distinguished Chair in Atmospheric Chemistry Dr Kimberly Prather is an expert on “how human emissions are influencing the atmosphere, climate, and human health,” according to UC San Diego. 

We asked her to take a look at the video to assess if what is happening in the video (the measuring device displaying high numbers) proves what is being said in the video (the levels of carbon dioxide are dangerous under the mask). 

According to Dr Prather, the device was being used in a way that it was not intended to be used. 

“These meters are not designed for this purpose. This is not how you measure CO2 levels in breath,” she told The Journal.

The CO2 monitor used in the video is designed to give a measurement of CO2 levels in a room, rather than the levels being emitted directly from an individual’s mouth and nose. Breathing on it directly will not give it an accurate reading, according to Dr Prather. 

“If you breathe on these meters, you can make it go really high but that is not the correct level because the device is not the proper device for those measurements,” she said in an email. 

Multiple governments state that these types of CO2 monitors should be placed away from people when taking a reading. 

The Irish government’s advice to schools is that these monitors should be placed at least 0.5 metres away from people. The Welsh government says similar: it advises placing carbon dioxide monitors “at least 0.5 m away” from people, stating “closer than this could give inaccurate readings.” 

The UK Health and Safety Executive advises that CO2 monitors should be placed “over 50cm away from people as their exhaled breath contains CO2.” 

An American study measured the carbon dioxide and oxygen saturation levels of a small sample of 50 people with and without a mask using a transcutaneous sensor. The sensor was non-invasive and was attached to the skin where it monitors blood gasses. 

The research found that there were “no statistically significant differences” in either carbon dioxide or oxygen saturation levels “between measurements without a mask and those taken while wearing either kind of mask.”

Carbon dioxide particles can’t get trapped in face masks, according to the American Academy of Pediatrics

“Carbon dioxide ​molecules are very tiny, even smaller than respiratory droplets. They cannot be trapped by breathable materials like cloth or disposable masks,” they said in a publication. 

“In fact, surgeons wear tight fitting masks all day as part of their jobs, without any harm.”

One potential source for this misinformation around carbon dioxide in masks is a study published earlier this year by the Journal of the American Medical Association (JAMA), which said it found that carbon dioxide levels of children increase when they wear a mask. However, as The Journal previously reported, it was retracted just over two weeks later. One of the reasons given was the wrong device was used to measure CO2 levels inside the facemask which didn’t give an accurate reading of how much carbon dioxide was actually being breathed in. 

According to the JAMA retraction notice, there were concerns “whether the measurements obtained accurately represented carbon dioxide content in inhaled air.”


The device used in the clip is not intended to measure CO2 levels in the body. Inserting a device used to measure CO2 levels in environments into a mask and breathing directly on to it would produce an elevated result.

The device at the end of the woman’s demonstration shows a reading of 10,000 parts per million, twice the level that death could occur at according to her claims. Yet in the clip she appears ok and able to talk about the risks masks pose to children. 

An expert we spoke to called the claims in the video “100% wrong and dangerous misinformation.”

We rate it: FALSE’s FactCheck is a signatory to the International Fact-Checking Network’s Code of Principles. You can read it here. For information on how FactCheck works, what the verdicts mean, and how you can take part, check out our Reader’s Guide here. You can read about the team of editors and reporters who work on the factchecks here.

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