Funny how we take little sayings for granted. Google defines “there is light at the end of the tunnel” as ‘the end of a difficult situation or task,’ or ‘the solution to a difficult problem.’ Clearly they did not take into account the development of a mask made for COVID protection.
The ‘light’ in question is in the Ultra violet C  part of the spectrum. The LEDs that we use produce light at various wavelengths within the Ultrav Violet and can concentrate the generation of these wavelengths into specific peaks known to compromise pathogens and viruses, rendering them harmless.

Various pathogens and viruses will absorb Ultraviolet light more readily. In simple terms, it gives the virus fatal sunburn, making it inert. I mean, the last time I had sunburn I got pretty inert for a day while laying on a bed covered in aloe vera gel. It was very painful and I was not able to do much. Exposing the virus to a high dose of ultraviolet C is the equivalent of putting the virus to bed, indefinitely.

Depending on wavelength and exposure time (the amount of time needed for the virus to absorb enough UVC light to render it inert) we had to calculate the flow of air through the mask and the energy per square centi millimeter of UV light required for the LEDs to do their job. In designing the chambers (plural because we treat air entering the mask in addition to air being sent out of the mask after you exhale) we placed 2 ultltraviolet LEDs in each chamber and ran them at 4x the energy requirement, just to be on the safe side.

Any virus that happens to make it through the particulate filters and (optional) N95 filters will get zapped.

The “end of the tunnel” takes the air flow in quite different directions. The AIR-IN chamber passes the airflow through a valve that lets air in but almost no air out, using a no-moving-parts valve that was developed over 150 years ago by a famous inventor whose name now graces a large electric car company, Tesla..The air flows into the chamber where it is exposed to the UV then enters into the main space of the mask, which is the face piece that the wearer inhales through.

From there it tries to exit through the same path it entered, only getting exposed again and being shut down by the AIR-IN valve. In a split second it finds an easy route through the second chamber, a separate AIR-OUT valve that is pulling the air through with the assistance of the out-fan.

Gases are exposed to additional LEDs in the second chamber and allowed to exit through the out-end of the mask with the help of the out-fan. The two fans continuously provide a constant airflow between the IN and OUT chambers.

We initially tried to use only one fan and found that it worked great when breathing in one direction, but since humans breathe in and out (that’s two directions) one of these directions is going to make it hard for the wearer to fight the direction of a single fan. It placed a huge load on the bearings and operation of the fan, and worse, it made fans whine noisily while reducing the life of the fan. So we used two fans. It was just the right thing to do.

All the light is contained inside the chambers. We do not let UV light leak out of the chambers or out of the mask in any way.

The other little titbit of information is that we as humans are not able to see the Ultraviolet spectrum; this is another modifier to the “light at the end of the tunnel” because the light can’t be seen. Some LED manufacturers provide a violet blue light that engages at the same time the UV light is being generated to let us poor humans know that it’s doing its business.

It also signifies not to look at the light source because in the same way the Ultraviolet compromises the virus, it can also compromise the delicate rods and cones that make up your eyes, damaging them. In other words, it’s dangerous to look at the light (that you can’t see).
Manufacturers of LEDs provide the tiny light sources mounted on heatsinks; a piece of conductive metal that dissipates the intense heat generated by these marvels of technology. The chambers act as extended heatsinks to pull the heat away from the LEDs more efficiently while they are doing their job.

In short, “the light at the end of the tunnel” has taken on a new meaning…
While it still holds meaning as ‘the end’ of a difficult situation, it has even more meaning to us and our future wearers of the mask.

There is so much more going on, but for now we can see (or not see) light at the end of the tunnel. Next time you casually use a phrase or saying, consider what we did to give you the most protection possible within this mask.

I love this journey of exploration.

Be safe and stay curious

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