Dead cells yes but i dont think you could define the accumulated quantity of this as dust, and with good air circulation and exhaust filtration that shouldnt be a problem. If they did give off a considerable amount of "dust" i would surely see it on the black/white sheeting?
I agree with you on the dry soil though but the particle would be much larger and more visible.
Like you said dust will gather on all parts of a fan, not just the central axis point. But in context of how the air is being used, when the air is forced against a solid object it will disperse in all directions. When the aiflow cannot escape in all directions it will take the easiest route ( just like water and electricity) which is out both sides due to the profile of the heatsink meaning there would be no low pressure zone underneath the fan to gather any "dust".
What do you mean by 12V ac/dc? It has to be one or the other lol!?
Cotton and sisal actually have similar flash points, your light may not get to a high enough temperature to ignite it but i bet an electrical arc could! Also sisal is more hygroscopic than cotton, high humidity can mean it could absorb some of this moisture and become a haven for mould to grow! This would be the case for cotton also though, thats why i stick to good old stainless steel ✌
When the airflow of an axial fan hits a surface most air will go out sideways, but under the hub the two "waves" of air pressure turn into vortices which will create a "dead" area where the two vortices collide. As crud builds up, that area grows. So that's where the crap starts building up. Pulling outwards has a similar effect as the main airflow is around the hub, creating an area where crap will build up. But you have temps under control so only monitoring is necessary and it's always good practice to clean things out between grows anyway to keep crud down. A few minutes of "routine maintenance" never does harm.
Enough dust build up is not necessarily visible particles until they clump together, and I've explained where this happens with an axial fan. You may hardly even feel it on the walls of your tent, or just assume that it's condensation or something due to temperature differences between the inner and outer walls. But you have disturbed particles when you touch the wall, and as that gets sucked over to your exhaust some will also be drawn into your fans. And not all particles actually go into your filter, some will land on the ducting due to vortices and then fall off, adding more microscopic crud straight into fans. And, as said, nobody runs a "Condition Clean" room with intake filters that can stop Sarin or nuclear fallout, although a survivalist bunker would be one hell of a grow room, so that's more crud.
I say all of this because I've had the "joys" of sorting out the damage caused by build up, and you wouldn't believe how much there will be in a year and is, as I've said elsewhere, quite a plausible reason a lot of these "cheap" chinese grow lights go "pop" after a year or two, it's because cooling has been compromised as nobody thinks about cleaning them out.
Anyways, led lights. No, you do get 12v AC/DC as they are replacement spots for AR50 MR16 fitting, as in these 12v downlighters in the bathroom ceiling, to be used instead of halogen lamps. The notion is that the cob does not need the transformer part of a driver, but only has to rectify, stabilise, etc, the "traditional" 12vac going to the halogen so, well, any fool can change a lightbulb, even me, meaning that you don't have to replace the existing transformers with drivers. You also get them in BA15 AR70 form, amongst others. Needless to say, after testing several different brands with several different types of transformer only, the decision was made to use proper drivers as there was not one combination found which did not flicker to some extent due to the on board circuitry not doing it's job properly.
As far as the string goes, a bigger worry is the plate edges digging in and cutting, hence the use of double sided tape around the edges to lessen that risk. But sisal also as lower flammability problems, it will self extinguish when charred. And it gets changed with every grow as SOMETHING changes as I shuffle things around, so fungus is not an issue, not at my humidity levels.
