What would this say about subculture gatekeeping? About immigration policy?
First, we have to ask: what's the purpose? Generally aircraft try to get up to their cruise speed quickly and then spend most of their time cruising, and you optimize for cruise first and takeoff second. Do we want multiple cruise speeds, eg a supersonic bomber that goes slow some of the time and fast over enemy territory? Are we designing a supersonic transport and trying to reduce fuel usage getting up to cruise?
And then, there are 2 basic ways you can change the bypass ratio: you can change the fan/propeller intake area, or you can turn off turbines. The V-22 has a driveshaft through the wing to avoid crashes if an engine fails; in theory you could turn off an engine while powering the same number of propellers, which is sort of like a variable bypass ratio. If you have a bunch of turbogenerators inside the fuselage, powering electric fans elsewhere, then you can shut some down while powering the same number of fans. There are also folding propellers.
The question is always, "but is that better"?
On the other hand, the hydrogen pushing against the airship membrane is also an electrostatic force.
Yes, helium costs would be a problem for large-scale use of airships. Yes, it's possible to use hydrogen in airships safely. This has been noted by many people.
Hydrogen has some properties that make it relatively safe:
and some properties that make it less safe:
Regardless, the FAA does not allow using hydrogen in airships, and I don't expect that to change soon. Especially since accidents still happen despite the small number of airships.
In any case, the only uses of airships that are plausibly economical today are: advertising and luxury yachts for the wealthy. Are those things that you care about working towards?
IKEA already sells air purifiers; their models just have a very low flow rate. There are several companies selling various kinds of air purifiers, including multiples ones with proprietary filters.
What all this says to me is, the problem isn't just the overall market size.
Apart from potential harms of far-UVC, it's good to remove particulate pollution anyway. Is it possible that "quiet air filters" is an easier problem to solve?
I'm not convinced that far-UVC is safe enough around humans to be a good idea. It's strongly absorbed by proteins so it doesn't penetrate much, but:
And really, what's the point? Why not just have fans sending air to (cheap) mercury vapor lamps in a contained area where they won't hit people or plastics?
As you were writing that, did you consider why chlorhexidine might cause hearing damage?
That works well enough, but a Vital 200S currently costs $160 at amazon, less than the cheapest variant of the thing you linked, and has a slightly higher max air delivery rate, some granular carbon in the filter, and features like power buttons. The Vital 200S on speed 2 has similar power usage and slightly less noise, but less airflow, but a carbon layer always reduces airflow. It doesn't have a rear intake so it can be placed against a wall. It also has a washable prefilter.
Compared to what you linked, the design in this post has 3 filters instead of 2, some noise blocking, and a single large fan instead of multiple fans. Effective floor area usage should be slightly less, but of course it has to go together with shelving for that.