Relax, the sky is not falling, if you follow what Sergei advised you will be fine. As some here have written, HPA is very dangerous if used incorrectly, but so is driving a car to work. But they don’t own a Altaros Booster.
I do not own or have I used a Altaros bottle to bottle Booster, however, I have used various boosters over a 10 year period, including the Altaros Shop driven air/supplied unit I have used for 2 years.
The first one, a booster I had 10 years ago just scared the bejesus out of me, however at the time scuba set up units did also, however, I was uninformed, if used properly they are safe. I sold or traded that unit to Doug for cash or his splendid AF mods. He used it with helium, and I think it is still going, and he is still with us.
Then came 3 generations of Shoeboxes, I would still be using them if support had been available.
Then I purchased the Altaros Booster 2 years ago. I ended up with a bunch of money in it, but it works, it is robust, very cool running and very quiet and above all is safe. All of my journey on my system has been guided by the advice I quickly received by email from Altaros and AGN member Chickentheif, an abtasive fellow but a walking vessel of Airgun/compressor knowledge none the less.
At the time of my purchase, I could have gone with the Bottle to bottle system, but I have no transportation to a dive shop and I am not a diver. My daughter and son-in-law have 80 or more scuba tanks, but they live half a world away in Maui. So I went to a shop Compressor driven/supplied unit. I eventually went to running 3 quiet CaliforniaAirtools units to reliably run my Altaros Booster. It is Shoebox slow, maybe a bit faster and in 2 years flawless, advice and rebuild kits are quickly coming if needed, I bought a few rebuild kits, but that is just me.
If I lived in Maui, I would be using the bottle to bottle unit, which I have read is much faster.
HPA is very dangerous, but following the instructions you get from Altaros and knowledgeable members experienced in the equipment your inquiring about will keep you safe.
Good luck on your quest for knowledge,
Roachcreek
P.S.
I went with the 3 CAT oilers 110V compressors because I did not want the oil smell a large powerful compressor can put out, nor did I want to retire my shop. My 3 CATS are easily replaceable and CAT tech is just a phone call away. The set up I run is quiet enough that I can’t hear it unless I am in our attached garage.
My set up.