Importance of Mask Fit

You should always feel more protected when wearing a mask. Many masks make claims of military grade filtration, or have numbers like 99.97% as part of their marketing. The trouble is, that filtration score can be achieved when strapping the filter fabric to a test machine, which doesn't give you a clear picture of how well the mask will filter the air you breathe. 

In reality, there are two parts to high filtration scores. First, how well does the mask filter out particles in the air? Second, how well does the mask fit your face? You may have heard people talk about N95 respirators and how wearing one requires the wearer to get professionally fitted. Medical workers typically get fit trained and fit tested before using a new mask on the job. So, what is mask fit, and why is it so crucial in mask performance? And is it possible to have a mask fit well, without getting fit trained? We'll cover that, but first let's talk about filtration.

Standard testing uses particles between 0.3 and 10.0 microns and produces various percentage scores. In general, filter material with higher ratings are better at filtering out air particles. However, there is another essential factor to consider breathability. Breathability is the amount of resistance you feel when wearing the mask. Overall, you want high filtration with low resistance (good breathability). We dive into the certification ratings (like N95, N99, etc.) in our Face Mask Comparison Guide. Understanding these scores is helpful when considering filtration.


So, what is mask fit?

For a mask to fit well, it must create a good seal with the face so that all of the air you breathe comes in through the filter. Common face masks have a wire in the nose bridge to conform to your face and create a better seal. This is a common feature that attempt to improve mask fit. If you happen to wear glasses, you know that a poor seal will result in your glasses fogging up because exhaled air faces lower resistance to go around the filter instead of through it. That's an easy way to identify a fit issue, and unfortunately poor fit affects the air that travels in both directions. The more unfiltered air, the lower the percentage of actual particles blocked by the filter. In fact, a recent study found that as much as one third of the air inhaled can go around the mask when there is poor fit. Reducing the effective filter performance by 33%. Sometimes, this resulted in filtration performance similar to common surgical masks, or an overall score of around 30-40%.

Breathing resistance comes into play because a mask with higher resistance and poor fit will force a higher percentage of air around the mask, meaning that the mask's actual filter performance can be even worse. Many cloth masks with "military grade" high filtration claims often fall into this category.

How can you tell if a mask will fit you well?

First, there is the overall size and design of the mask. Disposable or cloth masks don't adapt to the wearer's face and tend not to produce a good seal. The clear exception here is a disposable N95 respirator. Most of these fit nicely on a variety of face shapes. For inexpensive masks, look for the nose wire, adjustable ear loops, and take the time look for reviews by medical professionals. For reusable masks, look for masks with elastomeric or silicone face pieces that mold to your face and create a good seal. There are different approaches here, but we recommend looking for small and light mask that doesn't require many steps or adjustments to put on.

With the Woobi mask the first step is to put the mask on, and then adjust the length of the straps so the mask is snug, but not tight. The face piece should rests comfortably on the face. The Woobi sits against the chin instead of below it. This creates a more reliable seal when the wearer talks, moving their jaw up and down will e less likely to break the seal. It also works well for those with facial hair, as the bottom of the mask rests more on skin and less on your beard. This also keeps the overall size and weight of the mask low, making it easier to wear for long periods of time.

There is also a Child size of the Woobi Mask, the Woobi Pop. The Woobi Pop is for children ages 6 and up. You should consider sizing up to the Adult Woobi Plus once your child is the size of a small adult. This usually happens around the age of 11 or 13. The Adult size Woobi Plus will fit a wide range of adult faces. The adult mask should accommodate from a size small to Large. A good point of reference is the overall height. The Woobi Plus measures 4 inches tall. If you measure from the Bridget of your nose down, this will give you a good indication where the mask will sit on your face. 

In regards to fit training and fit testing, is there anyway to ensure good mask fit without a proper fit test? That depends on the mask. For common cloth masks, or disposable masks it's very difficult to perform a fit test without special equipment. But, a good rule of thumb is that the mask will typically not be able to create a good seal unless it has been N95 or KN95 certified. Even then, you would need go to a fit test center. The issue here is that the fabric of the mask itself is the filter, and it's difficult to isolate the filter performance from the seal.

For reusable respirator style designs like the Woobi Mask, it's very easy to verify fit by performing a seal check. Because the mask isolates the air that you inhale and exhale through specific ports in the mask exterior, you can cover the inhale port and perform a negative seal check. First, cover the inhale ports on the filter pod, and then inhale gently. If you have a good seal, the inhale action will create negative pressure inside the mask, causing it to press down against your face. If you don't have a good seal, the perceived mask pressure against your face will roughly stay the same, and you may notice air rushing in along the side of your nose, or in another area. Simply adjust the mask position on your face to create a better seal, and repeat the test.

Performing an ad hoc seal check can provide peace of mind and ensure that all the air you breathe is passing through a high grade filter. If you perform the negative pressure seal check and are unsure about the quality of the seal, you can also reverse the process and perform a positive pressure seal check. Cover the exhale ports, and exhale gently into the mask. If you feel the pressure inside the mask increase, and the mask puff up, then you have a good seal. If you feel air coming out somewhere, adjust the mask and retest. It's perfectly normal to need to adjust the mask position one or two times before feeling confident that you have a good seal.