Pretty exact number you quoted there. What’s so special about 30.2m relative to 29 or 31m? I can easily move my arm, where my wrist dive computer is on it, up and down and change my depth by 1m.
Some divers, DIR and some agencies promote helium at 30m already. That is in my eyes for 99.9 % of the dives around 30m way too shallow, too expensive and a waiste of the expensive rare helium. I have never used a 30/30 or a 32/30 which is 'the' gas to use then (30/30). I never found that even in currents and only pull and glide possible that ean32 was not the best gas for me. Cheap, better than air. I never felt myself overbreathing a regulator then.
I havent done such circumstances on ccr ( northsea wrecks), only oc. But did caves like Ginnie and little river on air diluent. But the conditions there are easier than on the northsea. But if you want to use a trimix then, already at 30m, no problems. I dont pay your bill.
Helium or not is a personal thing. But be a thinking diver. The 30.2 is an example as 30m is the limit.
The depth you start using helium is personal and somewhere between 30 and 60m. But all divers I know that decide to use deep air take also decogases. I dont know any diver that says are is the best at 60m. Yes I know divers that say we dont need helium at 60m, but they still take decogases and this is a small group. More divers take helium from 55m. And most from 45m. Also only a few from 30m.
For myself it depends on temperature, ccr or oc, currents, etc. But 99% of my 50m dives or deeper is on ccr with high helium.
Ccr gives you more options, onboard and offboard diluents can be different and switched if you want.
I knew one diver that dove regularly to 70,80,90m bounces on air, but he was lost last year on such a dive and still never found back.
But as soon as people start a decompressiondiving course, they never go back to deco on backgas.
The effects of narcoses can change from diver to diver, and from dive to dive. Yes it is interesting, and yes it is such a nice feeling in your hands if you go down as fast as possible to 45m ( it dissappears after a few menutes, but you feel completely zen then
)
But to state air is safer, that is not true. 50m on air is also not directly dangerous. But 60m means going over extra limits as po2, wob, etc. So do a course, entry level tx course brings you to 51m on 21/35 and max of 15 minutes accelerated deco. Then you can feel the difference between air and tx.
And maybe change your mind. Start becoming a thinking diver.
