Fact Check

Are These Claims About the Effectiveness of Face Masks True?

Widely shared posts from the summer of 2020, purportedly citing the CDC and U.S. Occupational Safety and Health Administration, offered numerous claims but little evidence.

Published June 18, 2020

Updated July 15, 2020
Image via Wikimedia Commons and U.S. Customs and Border Protection (Wikimedia Commons and U.S. Customs and Border Protection)
Image via Wikimedia Commons and U.S. Customs and Border Protection
A Facebook post is correct in saying N95 masks, surgical masks, and cloth masks can be dangerous and/or ineffective in protecting against the spread of COVID-19 based on CDC and U.S. Occupational Safety and Health Administration (OSHA) guidelines.
What's True

N95 respirators with valves do allow unfiltered exhaled air to reach others, increasing the risk of spreading infection. Cloth and surgical masks do not protect the wearer from airborne infection. Cloth masks also get dirty easily, which is why OSHA and CDC recommend regular washing.

What's False

However, contrary to the posts, OSHA and CDC have not recommended against wearing face coverings of any kind. Also contrary to the posts, cloth and surgical masks are not entirely ineffective because they prevent the wearer from transmitting infection to others through droplets. Surgical masks also protect wearers from getting potential infections via droplets. In addition, people who wear these masks are in little to no danger of breathing in too much carbon dioxide.

Another day, another viral claim about the effectiveness (or not) of face masks amid the coronavirus pandemic of 2020.

A popular Facebook post that had been copied and pasted numerous times in June repeated spurious but familiar claims about masks, this time selectively citing U.S. Occupational Safety and Health Administration’s (OSHA) recommendations:

In July 2020, a similar post — this time attributed to the Centers for Disease Control and Prevention (CDC) — made almost identical claims about N95 masks, surgical masks, and cloth masks. This photo circulated online:

The lengthy posts focused on three different types of protective masks: N95 masks, surgical masks, and cloth masks. We tackle assertions about each one below.

N95 Masks

According to the posts your unfiltered, potentially infectious breath could harm others if you are breathing through an N95 respirator.

N95 masks: are designed for CONTAMINATED environments. That means when you exhale through N95 the design is that you are exhaling into contamination. The exhale from N95 masks are vented to breath straight out without filtration. They don’t filter the air on the way out. They don’t need to.

Conclusion: if you’re in Stewart’s and the guy with Covid has N95 mask his covid breath is unfiltered being exhaled into Stewart's (because it was designed for already contaminated environments, it's not filtering your air on the way out)

This is mostly true, except it only applies to N95 respirators with valves. Such masks were designed for construction/factory workers or miners, to keep out dust and other particles, but not to prevent infectious particles from leaving the mask. When the wearer inhales, the one-way valve closes so pathogens can’t get through, but when the user exhales, the valve opens. In May, the San Francisco Department of Public Health tweeted that N95 masks with valves in the front weren’t safe and "may actually propel your germs further."

Hospitals largely use N95 masks without valves for this reason, and in accordance with Centers for Disease Control and Prevention (CDC) recommendations. OSHA's guidelines on N95s primarily focus on how they are meant "to prevent workers from inhaling small particles, including airborne transmissible or aerosolized infectious agents," and should be required in workplaces where respirators are needed.

Surgical Masks

The Facebook post argues that wearing a surgical mask makes you a "walking virus dispenser," as follows:

Surgical Mask: these masks were designed and approved for STERILE environments. The amount of particles and contaminants in the outside and indoor environments where people are CLOGG these masks very Very quickly. The moisture from your breath combined with the clogged mask will render it “useless” IF you come in contact with Covid and your mask traps it You become a walking virus dispenser. Everytime you put your mask on you are breathing the germs from EVERYWHERE you went. They should be changed or thrown out every "20-30 minutes in a non sterile environment"

OSHA guidelines seem to contradict some of these claims, arguing that surgical masks protect workers "against [potentially infectious] splashes and sprays," and also "contain" the wearer's respiratory droplets to protect others. OSHA says these masks should be placed on sick individuals to prevent transmission via droplets. Surgical masks do, however, offer ineffective protection from transmission via airborne particles due to their loose fit. While the post argues that such masks should be thrown out every 20-30 minutes, OSHA simply recommends that they "should be properly disposed of after use."

Cloth Masks

The Facebook post's and letter's claims about cloth masks are mostly false and have been debunked by Snopes before. The author claims:

Cloth masks: today three people pointed to their masks as the walked by me entering Lowe’s. They said “ya gotta wear your mask BRO” I said very clearly “those masks don’t work bro, in fact they MAKE you sicker” the “pshh’d” me.

By now hopefully you all know CLOTH masks do not filter anything ... ALL of them offer NO FILTERING whatsoever. As you exhale you are ridding your lungs of contaminants and carbon dioxide. Cloth masks trap this carbon dioxide the best. It actually risks health. The moisture caught in these masks can become mildew ridden over night. Dry coughing, enhanced allergies, sore throat are all symptoms of a micro-mold in your mask.

OSHA guidelines already state that cloth masks are ineffective filters against airborne particles. They are worn to protect other people from risk of infection via respiratory droplets. People wearing them are in little to no danger of breathing in unhealthy amounts of carbon dioxide. The posts point out the danger of dirty masks, which is why both OSHA and CDC recommend washing cloth masks after use.

OSHA also "generally recommends that employers encourage workers to wear face coverings at work," contradicting the argument of this entire post.

Finally, the author of the Facebook post claimed to be "OSHA 10&30 certified," which refers to OSHA’s 10-hour and 30-hour training modules about common health and safety hazards in the workplace. We reached out to OSHA, and a representative told us that these courses "do not include COVID-19 topics," nor does OSHA "certify" trainers.

Snopes also reached out to the CDC about the photograph of the notice. They directed us to their guidance on cloth masks, and issued the following statement:

CDC typically does not issue guidance or recommendations to the public in such a format. CDC’s guidance and recommendations are distributed on the agency’s website, official social media accounts and through news media.

In sum, the varied claims in these viral posts (with their dubious origins) for the most part misrepresented information provided by OSHA and the CDC. Scientific wisdom argues that wearing a mask is more effective than doing nothing, and, combined with social distancing and other safety measures, offers protection not only to the wearer but to others. Given these posts' combination of only a few correct facts and largely incorrect conclusions, we rate their various claims as "Mostly False."


Centers for Disease Control and Prevention.   "Considerations for Wearing Cloth Face Coverings."

Centers for Disease Control and Prevention.   "How to Wash Cloth Face Coverings."

Centers for Disease Control and Prevention.   "Infographic - Understanding the Difference, Surgical Mask, N95 Respirator."

Ibrahim, Nur.   "Is It Dangerous to Wear a COVID-19 Protective Mask for Too Long?"    Snopes.   8 May 2020. 

Mikkelson, David.   "Are Non-Respirator Masks Ineffective at Protecting Against COVID-19?"    Snopes.   19 May 2020.

Occupational Safety and Health Administration.   "COVID-19 Frequently Asked Questions."

Occupational Safety and Health Administration.   "Outreach Training Program (OSHA 10-Hour & 30-Hour Cards)."

Plater, Roz.   "A Certain Type of N95 Mask May Do More Harm Than Good."    Healthline.   16 May 2020. 

The Conversation.   "Why Wear Face Masks in Public? Here’s What the Research Shows."    4 April 2020.

Wilson, Mark.   "What is a Mask Valve, and Why are Cities Banning Them?"    Fast Company.   28 April 2020. 


Updated with new information.

Nur Nasreen Ibrahim is a reporter with experience working in television, international news coverage, fact checking, and creative writing.

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