One particular novelty mask has been making the rounds on Twitter lately: The Proper Mask.
We have tested this mask in our lab and have found it to perform poorly due to an intrinsically faulty design. Like many other low-end masks, it only provides minimal protection against dangerous aerosols.
We strongly recommend against using The Proper Mask and similar low-end FFP2 masks.
High-quality tri-fold FFP2 masks such as 3M Aura or Dräger 1920 will provide much better protection. If an adhesive mask is required, such as for MRI imaging, the Readimask (which we also tested and found to be much more adequate) is a safer alternative.
The vendor makes a number of lofty claims in their marketing material and packaging, such as:
Suggested uses include medical uses, dentistry or "whenever patients need extra protection".
The masks have a FFP2 CE certification and are claimed to be tested by reputable institutions, including a test report by PALAS and multiple tests done by Technische Universität München.
Overall, the vendor advertises this mask as being particularly safe and protective. It is our opinion that this is an inaccurate characterization of the product's (mediocre) performance.
We have tested a batch of "The Proper Mask" with lot number WD23081401 and production date 20230814 using a factory-calibrated TSI PortaCount 8048 fit testing device.
TSI PortaCount is a fit-testing device which uses environmental aerosols to measure real-world mask performance as worn on an actual face. It does so by comparing ambient aerosol concentrations inside and outside the mask while the user performs a standardized set of exercises.
We diligently followed the manufacturer's instructions on how to apply the adhesive mask on the test person's face. We repeated the experiment multiple times.
A fit test protocol ("OSHA FAST-FILTERING FACE" protocol) according to OSHA 1910.134 was performed using TSI's Fit Pro Ultra software.
The device was operated in "N95 mode", which is a less strict mode that uses a particle classifier to only count those ambient particles which a FFP2 filter filters most effectively.
We ran two tests, which resulted in total inwards leakage of 20% (harmonic mean fit factor of 5) and 9% (HMFF of 11), respectively. Despite the large difference in fit factor, there were no visible gaps or similar signs that would indicate improper sealing. The person testing the mask could not tell any difference and the mask felt very comfortable and well-fitted.
The mask consists of a blue fabric with an adhesive (blue) and an electrostatic filter media glued on top of it (white):
Unfortunately (and as previously noted by others), this design is fundamentally flawed. Outside air can pass through the blue part, leaving a large gap between the face and the filter media through which unfiltered outside air can pass into the mask. You can even see the light shining through the gaps in the fabric:
This is faulty design and cannot be used safely. The design of the mask also makes it very hard to put on correctly, as evidenced by the high amount of variability in our tests.
Similar products like the Readimask do not share this flaw, since their filter media covers the entire mask, with the adhesive being applied to the filter media. The Readimask's design is also much less error-prone since there's no cuts or "wings":
We repeated the same test on the Readimask and we achieved an overall fit factor of 133 in N95 mode, representing a total inwards leakage of only 0.75%.
The manufacturer provides a Mas-Q-Check test result by PALAS. The test validated the mask's total inward leakage with a test aerosol while applied to a plastic head:
In this test against an unnamed "Generic FFP2 mask", "The Proper Mask" had a leakage of 8.5% (similar to one of our measurements), while the "Generic FFP2 mask" had a leakage of 88.5%.
They go on to claim (from a single test using a single, poorly performing mask) that their mask is superior to "conventional FFP2 masks":
However, this is highly misleading - they must have picked the worst "Generic FFP2 mask" they could find, and the "competition" clearly didn't actually meet the FFP2 standard, given the absurdly bad leakage. It certainly does not support the claim of "best FFP2 mask ever tested" or "8x safer than other masks".
Good masks were hard to come by at the time when the design was originally devised (2021), and the design was clearly well-intentioned - compared to cloth masks and baggy blues, they would have been a slight improvement. However, neither the marketing, nor the mask's performance, have aged well.
The manufacturer also claims that "several studies were conducted at the TUM". We have not been able to find any of these publications, but according to the manufacturer, one concerns breathability under high performance physical exercise and another the filter retention capacity.
This is misleading, given that neither study makes any claim at all about the mask's safety. The breathability study did not test for leakage at all, and the other one measured only the filter without incorporating the rest of the mask, which is a useless metric.
The performance of the product does not match the manufacturer's boastful claims that it is better than the competition or even the best FFP2 mask ever tested.
Instead, it only barely meets the FFP2 standard, and only when the adhesive is applied very carefully.
"The Proper Mask" achieved total inwards leakage of 9% and 20% in our two tests. The FFP2 specification requires a total inward leakage (face seal leakage + filter leakage) of at most 8%.
Notably, the FFP2 standard is very forgiving. Modern high-quality FFP2 masks achieve much greater scores than required by the standard. For instance, 3M Aura, Dräger 1920 or 3M VFlex masks routinely achieve fit factors of 200 and higher (<0.5% leakage) in N95 mode.
It is our opinion that - just like many similar low-end "coffee filter"-style FFP2 masks - The Proper Mask is unsafe and unsuitable for protection against dangerous aerosols.
When it comes to protection against SARS-Cov-2, one-way masking is now the norm, putting a much greater emphasis on highly performing masks.
We are a non-profit research group and not compensated for our research. We are not affiliated in any way with any mask manufacturer, or any similar conflict of interest.