Has anyone ever heard of anything like this, says it allows gas exchange while keeping contaminants out?
Means keep your cap on… do not take it off…
and yeps… I say this all the time.
Letting it breath, or leaving the caps off, you will loose your flavor molecules… makes juices weaker.
Means you wont get the bang for your buck.
“Allows gas exchange while sealing out dust and contaminants.”
Bullshit. If the gases (volatiles) can get out then contaminants get in. Why is it that some people still believe leaving the caps off is a beneficial part of the steeping process? Just the act of filling and refilling your atomizer is more than sufficient for any so-called “gas exchange”.
Like @anon84779643 stated, leave the caps on for the duration of the steep.
it is not that the gasses can “get out” its more so that they “mingle” with the juice, helping it to age and steep correctly.
because too many spout the bs… and believe it the power of use more buy more…
Yeps 
is all that is needed. I mix mine up and depending on how much I want to vape it… it all happens naturally, which is for the best. 
@Olscratchy about the ONLY time you want to cap off, would be with heavy alcohol based flavs, but still, only cap off, then right back on.
and not even then…
time steeped with allow the liquid to absorb what is in the gases and all will be fine. 
I’m voting no on that Smoky.
When I mixed with some of the BCF Super Concentrate tobaccos and other flavors (alcohol based), I found that leaving the mix in the beaker overnight, with a coffee filter covering the beaker, did a really good job of letting the alcohol notes evaporate. Might have been my tastebuds… but, my mixes tasted as punchy as ever. 
100pct agreed…ime there has never been any need to " breathe " any liquids , reagrdless of the Carrier.
It all depends on the particle size and how porous the filter is and what you want to keep out and what not.
I do believe this is intended to let gases like alcohol escape your juice while keeping the flavor molecules inside your bottle and keep dust and other (bigger) particles away from your juice.
I’m sceptical, but I’ll say that only a test of it can prove or disprove its effectiveness. And since different flavors have different molucules, it would likely have a different effect on different juices.
I’m in the never breathe your liquid camp. Just wanted to say that I was expecting a film about steeping/breathing eliquid, so I had a chuckle when I saw the actual product!
I will let 1000 or so people swear by it b4 I decide to experiment with that one. On 2nd thought…nah 
My response is based on their claim. Keeping dust and other bigger particles out may indeed work at that level. But what about smaller molecules/contaminants? Would you feel good steeping your brews with those things in the middle of an industrial waste facility?
Did you see the Tanklets? Little bitty designs in glass that you put in your tank. Decorative. Silly! I could see my wife liking that, but she squonks.
I don’t know what state you keep your steeping cupboard in … a little clean up every so often never hurt anyone 
LOL you’re not alone, I thought it would it was a video too.
Not sure, but it sounds like you missed my point. 
Nevermind.
I thought the implied that I wasn’t being serious but yeah, nevermind