How do ASTM Level 3 masks stack up against the competition?

If you consider yourself a mask nerd, there’s a good chance Level 3 disposable face mask are on your radar. This type of face covering, officially known as an ASTM F2100 Level 3 Surgical Mask, is gaining a reputation as something of a contender in the world of protective face masks.

Level 3 masks are being described as an FDA-approved heavy-weight in a field full of questionable fabric masks, or even as a light-weight alternative to medical-grade respirators like the N95.

Is the hype around Level 3 masks deserved, or are these just scrubs trying to punch above their weight? Before putting your money on the line, here are some important differences between Level 3 surgical masks, N95-type respirator masks, and fitted cloth masks using PM2.5 filters.

Filtration

When talking about face mask effectiveness, we like to break things down into the three Fs: filtering materials, facial coverage, and fit. While filtration is not the most important of the three, it is usually the first thing people ask about, so let’s start there. Just be sure to keep reading, because even though contemporary Level 3 masks can compete with the big boys on filtration material and coverage, they tend to be outclassed when it comes to fit.

Level 3 Surgical Masks

By now you’ve probably heard the refrain that surgical masks are designed as barriers against fluids, not as barriers against airborne particles. Traditionally this is true. From a regulatory perspective, FDA-approved surgical masks, even the mighty ASTM F2100 Level 3s, are not engineered to filter the same degree of fine aerosols as N95-type masks and other industrial-grade filtering facepiece respirators. For you upper-level mask nerds, a certified Level 3 mask needs to filter a critical mass of particles between 100 to 5,000 nanometers (0.1 to 5 microns), but the test particles are typically at least 600 nm (0.6 microns) wide.

There’s now plenty of evidence that COVID can spread via much smaller particles than the kind surgical masks are designed to protect against. As a result, surgical mask manufacturers are racing to get their scrubs tested to the more rigorous levels required by the N95 standards. In fact, some level 3 masks score impressively well on these tests, achieving filtration efficiency comparable to N95 (or KN95) respirators in the ultra-fine aerosols range (75nm / .075 microns).* The caveat? These are the pre-fit scores. Keep reading, or scroll to the fit section below.

Surgical Mask Category Sub-micron Filtration Leakage Assessment Particle Size Tested
Level 1 >95 Not required .6 Microns (Lower) / 2 Microns (Upper)
Level 2 >98 Not required .6 Microns (Lower) / 2 Microns (Upper)
Level 3 >98 Not required .6 Microns (Lower) / 2 Microns (Upper)
N95 Respirators

N95 masks are the workhorse of respirators, and that’s because they work. A certified N95 respirator must filter at least 95% of particulates in that same ultra-fine aerosol range. The tradeoff with this consistently high degree of protection is reduced airflow, so people with certain pre-existing conditions are not advised to use medical-grade respirators on an ongoing basis.

PM2.5 Filter Masks

Unlike medical respirators and Level 3 surgical masks, a multi-layered "pm 2.5 mask" is designed to work in conjunction with a specially-designed pm2.5 filter insert, and vice versa. This unique approach can be confusing, and because pm2.5 filter masks are engineered to a Chinese standard rarely used outside of Asia, there isn't as much laboratory data for western consumers to evaluate when considering their mask options.**

Our advice? Think of a pm2.5 filter mask as a multi-layered fabric mask equipped with many of the facemask elements recommended by the CDC, but enhanced with a powerful electrostatic barrier that covers most of the mask’s face. The lab test for the pm2.5 filter itself is essentially the same as the N95 test, and a certified pm2.5 filter, like the ones produced by Puraka, can score as high as 99% on standalone efficiency testing.

Of course, because a PM2.5 filter isn't airtight, 99% isn’t the real score. Just like the Level 3 surgical masks that score high on materials filtration, you have to test for fit and leakage to know if the mask actually works. That's one of the main differences between a pm2.5 filter mask and a level 3 surgical mask: the pm2.5 mask standards require leakage to be part of the test, which we’ll discuss in the fit section. We’re getting there, we promise!

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Face Coverage:
Nose to Chin coverage
To achieve good coverage, a mask should cover your nose, extend under your chin, and be sufficiently wide. The under-chin extension is especially important for masks that are not sealed, like the Level 3 surgical mask and a fabric mask using a pm2.5 filter. They are also important if you have a beard!

In this case, Level 3 surgical masks, NIOSH-certified respirators, and pm2.5 filter masks are all designed to offer comprehensive coverage over these areas, so we can consider this box checked.

Now, let's talk about fit!

Fit:

Level 3 Surgical Masks

When considering Level 3 Surgical Masks, the most important factor to know and understand is how well these masks work when you factor in fit. Remember, unlike N95 and PM2.5 masks, Level 3 certification for surgical masks measures only the material itself, and doesn't account for how well the mask filters when worn on your face.

The ASTM F2100 specification offers up this caveat clearly, saying it “only evaluates the materials used in the construction of the medical face mask, and not the seal." The testing language under ASTM F2299 is even more explicit, stating: "the integrity of the seal to the wearer's face is not evaluated in this test".

To illustrate how much fit impacts a Level 3 Surgical Mask’s true filtration efficiency, let’s go back to the Level 3 masks mentioned above. These were the ones that scored similarly to a KN95 or N95 mask on a materials-only basis.

In one case, a popular FDA-approved Level 3 mask that scored 92% prior to fit testing, dropped to 77% when measured to account for fit. In another case, a well-known Level 3 mask that surpassed 90% on a materials-only basis filtered only 11% of particulate matter when worn by a real human being. This shows the dramatic difference between a surgical mask with good fit, and one with too many gaps. Mask tester Aaron Collins’ youtube channel shows a few of the tests.

Level Three Surgical Mask Pre-fit Score (Materials Only) Post-fit Score
Sample One 91% 11%
Sample Two 92% 77%
N95 Respirators

N95 masks are in a league of their own when it comes to fit, and this is by design. Under the NIOSH standards, N95 respirators must be fitted to the individual wearer in order to minimize gaps and create a seal between the wearer’s face and the outside world. When correctly fitted, an N95 mask achieves a filtration efficiency practically impossible to achieve with a Level 3 Surgical Masks or cloth mask and PM2.5 filter.

On the other hand, studies strongly suggest that because N95-type masks are rigid, even the very smallest gaps can cause them to lose a disproportionate amount of filtration compared to more flexible fabric masks. If you needed another reason to stay away from N95s - besides the fact that medical respirators are still in short supply and needed by health care professionals - this fact should be reason enough!