Do N95 masks restrict your sense of smell?

N95 masks, which have been a product hospitals in the United States have had to buy in bulk and wholesale during the last 10 months, are one of the main sources of protection in healthcare settings, along with face shields, disposable face masks, and other medical supplies.

With a popular COVID-19 symptom being loss of smell, could N95 masks restrict this sense in people? Let’s see what the studies show.

What are N95 masks?

N95 masks or N95 respirators are currently being used as the best face mask for virus protection in healthcare settings. They have a set of antiviral filtering properties that make them more effective for protection against COVID-19 or the flu than the usual face masks used in these centers, which are surgical masks.

Respirators are a specific type of face mask that filter out small particles that are not safe to be inhaled by a person. These particles, known as respiratory hazards, could potentially cause very serious health conditions in workers of certain filed, and respirators are required to protect these workers

N95 respirators in particular are made to filter out airborne particles, which are those with a size of 0.3 micrometers, that don’t contain oil, and they do so with an efficacy of 95%. This way, they’re effective for the protection of a wide variety of particles, like dust, smoke, pollen, and some bioaerosols.

Some of the most used models are 3M N95 masks, like the 3M 8511, 3M 8210, and 3M 1860. KN95 masks, usually thought to be a type of N95 mask, is a different type of respirator approved under a different set of standards. N95 masks are approved by an entity called NIOSH in the USA.

Does N95 masks restrict your sense of smell?

Since one of the most common symptoms of COVID-19 is the loss of smell, this question is of great relevance and importance. Currently, 5 to 85% of patients with this disease are reported to experience this symptom. For this reason, the correct assessment of olfaction is very important to screen out and isolate seemingly asymptomatic patients and prevent further transmission.

As one study explains, a subjective report of loss of smell is biased, so psychophysical measurements can provide quantitative criteria for the diagnosis of an olfactory deficit. But, since the coronavirus is spread through the respiratory droplets released by the mouth and nose, the evaluator must be protected and the patient should wear a mask.

However, whether or not the different types of face masks can affect the results of these tests is unknown. The study was performed on 20 people with an age of around 27 years old, equally distributed between males and females, as well as 10 people with some form of olfactory deficit with an age of around 56 years old distributed with 3 males and 7 females.

They compared both odor sensitivity and identification using a Sniffin’ Sticks test with and without surgical masks and N95 respirators. These tests are based on smelling a felt-tip pen with an odor.

In the experiment with the surgical masks, the people were put through two identification tests and two sensitivity tests, one with the mask and one without the mask. Then, they were equally and randomly divided into two groups where they had to go through a test with a mask. After the tests, they had a five minute break where they verbally rated the intensity of the odor on a scale of 0 to 10. The experiment was the same with N95 masks.

With N95 masks, the decrease in odor perception was strong, and none of the patients could finish the odor sensitivity and identification assessment with the N95 mask on. Many of them reported that only one-third of the felt-tip pens with an odor could be perceived. None of them could perceive the odor with the highest concentration.

This suggests and led them to conclude that N95 masks could represent a strong odor barrier, since few odor molecules could pass through the mask and reach the olfactory receptors. They also concluded that N95 masks impair olfaction to some degree, and could serve as a model for anosmia (loss of smell completely) in other experiments, while surgical masks only reduced olfaction partially, could be used as a model for hyposmia (reduced sense of smell).

This study also led them to conclude wearing both of these masks could affect or even prevent the detection of this common COVID-19 symptom. Their final conclusion is that odor identification is possible with face masks on, but the sensitivity test would have to be adjusted.

https://onlinelibrary.wiley.com/doi/10.1002/alr.22682

In a different publication, the detection of odors with N95 masks was analyzed. They explain that N95 respirators protect against airborne particles. Fit tests are performed on employees that require these respirators for protection, and they can be either qualitative or quantitative. The qualitative fit tests sometimes are based on the olfaction of a certain odor, where they usually use chemicals like saccharin or Bitrex.

Our olfactory receptors detect molecules, for example, like sulfur, which has a molecule diameter of around 0.0004 micrometers, which would allow them to pass through N95 masks. Smoke particles, on the other hand, are typically larger and would be filtered by the mask. So, whether or not a person can smell something would be based on the diameter of the molecule producing the smell.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7447000/

N95 masks are currently being reserved for frontline workers. A person in a high risk environment uses this mask for protection since reusable cloth masks won’t be enough. However, for both adults and kids, cloth masks are the recommended choice for daily activities along with social distance. Different designs and sizes can be found for sale online. 

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