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Face masks do not reduce the level of oxygen or increase CO2 levels to unhealthy levels?

Russell Setright

Russell Setright is an accredited medical writer, clinical researcher, Nutritionist, Naturopath, Herbalist, Sports remedial therapist, sports trainer, educator in Advanced Life Support, Critical Care Airway Management & pre-hospital emergency care and rescue. He was also a past Government Registered Naturopathic Physician, and is CEO of Emergency Medics Australia Pty Ltd.


Listeners to my radio shows have told me that wearing a mask can reduce your oxygen intake from 21 per cent to 16 per cent. They don't please read on.

This is NOT true, with the Health Departments advised use of cloth or non-medical and surgical, but not N95 masks, as used by the general population the data confirms that these masks are safe and effective. This statement could cause confusion and may be due to a misunderstanding of oxygen percentages during respiration and/or the use of specialty N95 masks for long periods.

I trust the following helps clear up the matter.

At sea level the air we breath in contains 21% oxygen and 0.04% carbon dioxide and around 16 % exhaled oxygen and 4% exhaled carbon dioxide in our breaths. Therefore, about 5% of breathed air is consumed in each breath. This exhaled air, an average ventilation of around 6 litres per minute, is passed through the mask with only a small amount retained in the dead-space by some tight fitting N95 masks and miniscule amounts in general use non-medical and cloth masks.

In the past, authorities that recommended against the community compulsory use of masks was not based on scientific evidence but mainly cited shortage of supplies, and that the public do not have the adequate skills to wear them, or that wearing masks might reduce compliance with other important behaviours. However, the current research rebuts this approach(6)

N95 masks

Some N95 masks, and even some cloth masks, have one-way valves that make them easier to breathe through. But because the valve releases unfiltered air when the wearer breathes out, this type of mask doesn't prevent the wearer from spreading the virus

Also, a tight (correct) fitting N95 mask has a dead-space that could be restrictive and may decreases oxygen, and increases carbon dioxide levels over lengthy use. These masks are for Healthcare professionals who are trained in there use and best not used for general wearing when shopping etc. unless medically prescribed(1)

Professor Jonathan Parsons, a pulmonologist at The Ohio State University stated. "Fortunately, the flurry of complaints has also given rise to a number of highly effective demonstrations in which medical professionals display their excellent oxygen levels while trying on different masks and sometimes multiple masks at once. Believe these demonstrations, because they’re true. Many professions require the regular use of masks, and the people who wear them don’t suffer as a result"(7)

General use masks (cloth and Non-medical)

A cloth face coverings or non-medical masks that are readily available and intended to trap droplets that are released when the wearer talks, coughs or sneezes. If everyone was to wear these masks it can help reduce the spread of the virus by people who have COVID-19 but don't realize it. These masks should cover your nose and mouth but not be tight fitting as this could make it harder to breathe.

A study at McMaster University using portable pulse oximeters in older people to measure their blood oxygen levels while wearing a non-medical face mask before and after use found, wearing a 3-layer non-medical face mask was not associated with a decline in oxygen saturation (blood oxygen levels) in older participants.(2)

I have also carried out the same experiment on myself and found no change in oxygen levels.

Because breathing may be slightly harder with some masks, people who suffer from severe COPD or pulmonary and/or cardiac disease, or persons with psychological disorders such as claustrophobia, anxiety, panic disorders, or other diseases that make breathing difficult, should only consider the use or not the use of face masks in consultation with their doctor.

Important Mask Care

It is important that all masks be changed regularly to avoid moisture and pollution build-up in the mask. Never reuse a disposable mask and keep the wearing of masks to times when required. Also, Don't touch your mask while wearing it, if you accidentally touch your mask, wash or sanitize your hands.


Bottom line is cloth and non-medical face masks work and don't cause worrying changes in oxygen or carbon dioxide levels. The best protection from infection in close quarters is a combination of social distancing, hand sanitising and face mask use as doing this could result in a large reduction in risk of infection(3)

The wearing of masks by the public, as well as international travel controls, are independently associated with lower per-capita mortality from COVID-19(4)(5)

Can Diet and Lifestyle Help?

Importantly, diet and lifestyle also plays an important role in helping promote a healthy immune system. Get enough sleep and exercise and ensure your vitamin D3, vitamin C and Zinc intake levels are sufficient(8)

Stay well and lets all work together and win against this pandemic.


  1. Physiological impact of the N95 filtering facepiece respirator on healthcare workers, Respir Care 2010 May;55(5):569-77.

  2. Peripheral Oxygen Saturation in Older Persons Wearing Nonmedical Face Masks in Community Settings, JAMA. 2020;324(22):2323-2324

  3. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis, the Lancet  VOLUME 395, ISSUE 10242, P1973-1987, JUNE 27, 2020

  4. Association of country-wide coronavirus mortality with demographics, testing, lockdowns, and public wearing of masks (Update June 15, 2020). ResearchGate June 15, 2020

  5. Face Masks Against COVID-19: An Evidence Review, Preprints 2 November 2020 / Online: 2 November 2020 (10:18:00 CET)

  6. Importance of Face Masks for COVID-19: A Call for Effective Public Education, Clinical Infectious Diseases, Volume 71, Issue 16, 15 October 2020, Pages 2195–2198

  7. Do masks cause lower oxygen levels? The Ohio State University Wexner Medical Center August 4 2020

  8. Setright R. Prevention and Treatment of Acute Respiratory Infections and Enhanced Immune Function, JATMS, Volume 26, November 2 2020

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