I found this in 4chan

[bayonetta97]

how reliable is this method?

 

[Redrock]

You have to check the gas purity, because they add air to the helium since 2015...

 

[F_ckthisplace]

If you can rely on the setup and not taking the gas mask off it's reliable

 

[drakewantstogo]

It was a very common method. Unreliable now since you can't find pure helium

 

[Pulpit2018]

You have to check the gas purity, because they add air to the helium since 2015...

What?How do you know this?
This sounds bad.

 

[Redrock]

What?How do you know this?
This sounds bad.

it is in the PPHb