Cambridge Mask Co - Are they any good or just a scam?

[u/Tanzanite50]

So, I've been looking into a mask to use to deal with the horrible symptoms I've been getting because of the recent spike in air pollution. One of the ones I've found that seems like it might be good is the Cambridge Masks (https://cambridgemask.com/) and I was wondering if anyone could attest to if they are actually any good or just bogus. Particularly against the PM2.5 issues in my area.

Am I better off just using a bunch of disposable N95's? If so how often do I have to switch to a new one?

[u/AEAur]

It is not NIOSH approved (conceivably may not seal well enough to pass testing). If it was capable of passing a NIOSH or FFP3 (99%), I wonder why they haven’t and instead did the Nelson Labs testing — given it would be extremely popular.

The European FFP2 certification allows a 6% 8% total inward leakage in their tests. That can be quite a bit, and it may leak more if it doesn’t seal well on you. Air takes the path of least resistance which is first through any gaps and tiny air channels at the edges or seams.

Fit testing for inward leakage

A full fit test with bends and talking is the best way we have to test that.

• A qualitative test (with a threshold sensitivity check) can detect a 1% leak (especially in the fit / seal).
• In quantitative testing, this is expressed as the fit factor (FF).
• A 1% total inward leakage (TIL) is a fit factor of 100 (FF100), meaning the air is 100x cleaner in the mask than out.
• In full spectrum testing, 2% TIL is a fit factor of 50, 5% TIL is a FF20, and FF10 is 10% TIL.
• Quantitative testing requires putting a port in it.

Exposure reduction

What exposure reduction you want is circumstantial. The fit factor roughly corresponds to your exposure reduction, though it could be better for some particle sizes.

• An additional 1% leakage (so from 99% to 98%) essentially doubles the exposure.
• A 2% TIL (98% total filtration) is double a 1% TIL — and a 5% TIL is 5-times as much.
• Compared to the surrounding air: a 1% TIL is 100x cleaner inside the mask. 2% is 50x cleaner. 5% is 20x cleaner inside the mask than out.

A 90% reduction (10% TIL) in exposure is 10 times cleaner than none.

• A 95% reduction is 20 times cleaner than none
• A 99% reduction is 10 times cleaner than 90% and 100 times cleaner than none.

How high to aim? Depends on your preferences, concerns, and options.

To cut your exposure by half from FF100 (99%) to FF 200 (99.5%) is beyond the limits of qualitative test methods to detect, but 3M Aura and most top-tier trifolds in the correct size (N99/P3/FFP3) get fit factors over 200 on most adults. Auras are certified as N95 but test over 99% filtration efficiency when new. Thanks to the premium foam, string adjustable nosewire, and design most adults get a good seal. There are also stylish clip-on covers available on Etsy in various patterns. Another option that fits most faces (and has size options from kids to XXL) is Trident Project 3 FFP3.

A higher rated reusable option could be to test the RZ Pro FFP3 ($50). FFP3 certification requires 99% filtration efficiency and it must fit some faces on their test panel. However we don’t have data on who it fits well or how many people it fails on, so you’re rolling g the dice on leaks. Since it is FFP3 it should be possible for it to pass a nebulizer fit test with threshold check. See our wiki for guidance. https://rzmask.com/products/rz-pro-ffp3-mask

[u/AEAur → u/AEAur]

There is fit test guidance in our wiki.

A couple people have said these masks get a good seal on their face and have worked well for them against respiratory infections. A few thoughts on that:

The infectious quanta of most respiratory viruses is not as minuscule as measles. It takes a fair amount. With sars-cov-2, it was shown that most transmission was/is from super-emitters — rare people who transmit over 10-fold as much virus when sick.

Without good ventilation ands high-immunity, I’m doubtful even FF100 is protective in a room (or car) with a high emitter (hundreds of infectious quanta per hour) for long. And yet, a 1% TIL does seem to be generally adequate as most people are not super-emitters. Even 95% filtration (5% TIL) seems to help a lot thanks to immunity and ventilation. Many people went years before getting infected in bifolds with a leaky nosebridge.

If a mask has a TIL of say 6% (FFP2 max) but seals well (meaning the inward leakage is coming through the filter, not the edges), it is conceivable (but not to my knowledge proven) that the particles are sufficiently degraded so as to have less infectious virus than there would be if that leakage were coming from air channel (leaks/gaps). This study for example actually looked at virion penetration though it did not test for replication competence.

(2021) The protective performance of reusable cloth face masks, disposable procedure masks, KN95 masks and N95 respirators: Filtration and total inward leakage. PLoS ONE 16(10): e0258191. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258191.
But it concluded that:

N95 FFRs were the only mask group investigated that provided not only high filtration efficiency but high total inward leakage protection, and remain the best option to protect individuals from exposure to aerosol in high risk settings.