Why N95 masks may not be as protective as you think

In the course of the pandemic, the prevailing thought has been {that a} high-filtration masks—such as an N95, KN95, or FFP3—ought to supply higher safety than a surgical or material masks. Nevertheless, recent research I carried out with colleagues on the College of Cambridge suggests this isn’t essentially the case. For these masks to be extremely protective, they need to correctly match the wearer, however typically they don’t.

That is itself a problem, however our analysis additionally found one other worrying factor: Folks aren’t superb at assessing whether or not their masks matches. Steadily, they use a self-assessment methodology to examine match, which we discovered to be unreliable. This implies folks may be performing as although they’re sporting a well-fitting masks after they aren’t, which will increase the danger of them catching and spreading the coronavirus.

Given this, we determined to conduct a second piece of research, to see if we might enhance the fit-checking methodology. This resulted in us creating a possible new manner of testing whether or not a masks matches that may be carried out at dwelling with supplies costing roughly $28.

Table of Contents


Good match isn’t common

Our first piece of research measured how properly totally different masks blocked ambient air particles from getting into them when being worn. This concerned taking steady measurements of the focus of air particles within the ambient air outdoors the masks as properly as within the air contained in the masks (through a valve related to it) after which variations between the 2 to see if air was seeping in.

That is what’s recognized as quantitative match testing. It’s a generally used and extremely dependable technique to take a look at masks match. The U.S. Occupational Security and Well being Administration (OSHA) mandates that for an N95 or comparable masks to be deemed appropriate to be used, it should rating above 100 in such a test.

We ran quantitative match testing with seven members, who every examined 5 several types of N95 masks, as properly as a KN95 masks and a surgical masks. Three members additionally examined some material masks. This meant N95 masks had been examined a complete of 35 occasions; solely in six cases did their scores exceed 100. When poorly becoming, we discovered the N95 masks supplied not way more safety than the surgical or material masks. The KN95 masks additionally carried out very poorly after they didn’t match, providing no extra safety than a material or surgical masks.

It subsequently can’t be assumed that high-performance masks are universally extremely protective. Correct match is important for cover, and even the very best performing masks, the 8511 N95, match solely three out of seven members. Some N95 masks, such as the Aero Professional and Xiantao Zong, didn’t match any of the members adequately.

Self-assessing match typically inaccurate

Earlier than measuring quantitative match, we had additionally had the members themselves assess whether or not they thought every masks match (what’s recognized as qualitative match testing). They did this by following the U.Ok.’s Nationwide Well being Service (NHS) guidelines: visually and manually inspecting the masks every time, rigorously feeling across the edge for air leaks, and adjusting the match as vital. We then had members price every masks on two standards—whether or not they believed the masks match and the way assured they had been of their determination.

We then in contrast these self-assessments with the extremely dependable, quantitative match information that we gathered. Within the linked graph, you can see how the precise and estimated match of the 5 N95 masks in contrast throughout the seven members. (There have been 4 ladies and three males, aged between 18 and 74. They are listed on the X axis.)

The peak of the bars reveals how properly the masks match—as talked about beforehand, solely six occasions did an N95 masks match properly sufficient to go the OHSA’s 100-point benchmark. The colour of the bars reveals what was predicted in every self-assessment: inexperienced means the participant thought it did match, crimson that it didn’t, and the darker the colour the larger the boldness of their prediction.


If predicting match precisely, bars above the 100-point mark are inexperienced and people beneath are crimson. So, as you can see, the members weren’t notably correct in assessing the match of the varied N95 masks. They appropriately recognized masks that did match, however frequently misidentified poorly becoming masks as being adequately in a position to defend them. There’s additionally no correlation between their confidence of their predictions and the predictions’ accuracy.

These findings advised that the self-administered methodology of checking match used on this research isn’t dependable and that another is required.

Easy methods to enhance self-assessment

We then had a go at creating a better method of qualitative match testing that would be carried out at dwelling for an affordable value.

In healthcare settings, a special methodology is used to check high-filtration masks. Reasonably than assess match visually and by contact, a substance with a sure style is launched into the air across the masks wearer. If they will style the substance, it signifies the masks doesn’t match correctly.

This method requires an acceptable enclosure, as properly as a flavored take a look at answer and a nebulizer to spray it into the air. These provides can be costly and, throughout COVID-19, tough to acquire. So, we showed how to copy this methodology at dwelling utilizing cheap options bought on Amazon for round $28.

[Source Photo: Natakorn Ruangrit/iStock]

An aroma diffuser can exchange the nebulizer, and may be used to aerolize saccharin dissolved in water into an enclosed area. The participant then assessments to ensure they will style this with out a masks on, after which sees if they will style it with a masks donned. To make sure an intensive take a look at, the consumer can transfer the diffuser round in order that its vapor touches all edges of the masks, or they might cowl their head with one thing—such as a densely woven towel—to assist focus the mist round their face.

It’s necessary to notice that whereas this methodology was proven to be efficient in our research, it’s not regulator-approved, and so ought to be used at one’s personal threat. We do not certify its security.

Eugenia O’Kelly is a PhD Candidate within the Division of Engineering on the University of Cambridge. This text is republished from The Conversation underneath a Inventive Commons license. Learn the original article.