O2 Question: Why is 40% O2 the threshold for the industry?

[Mcarlson]

Thanks to everyone who replied.

Several of the replies mentioned the percentage of O2 rather that the partial pressure of O2. The messages implied that concentrations were sometimes the governing concern rather than the partial pressure. Maybe I misunderstood.

Partial pressure, as I understand it, governs the reactivity of the gas. The partial pressure of O2 in 3000 psi air is 627 psi, so why would pure O2 at 500 psi be any more reactive (and hazardous)?

 

[boulderjohn]

Thanks to everyone who replied.

Several of the replies mentioned the percentage of O2 rather that the partial pressure of O2. The messages implied that concentrations were sometimes the governing concern rather than the partial pressure. Maybe I misunderstood.

Partial pressure, as I understand it, governs the reactivity of the gas. The partial pressure of O2 in 3000 psi air is 627 psi, so why would pure O2 at 500 psi be any more reactive (and hazardous)?

There are two issues that are very separate. One is the danger of dealing with the gas on the surface---fire or explosion while the gas is being handled. The other is the effect on the body, which means the danger of oxygen toxicity to the person breathing it.

 

[BRT]

i AGREE. tHE NANNY Justification IS THAT SOMEONE COULD MAKE 23.5% AT GREATER THAN 50 PSI USING PARTIAL BLENDING AND (oops) could have greater than 40% in it,,, in the process. Its the one rule fits all syndrome. If your tank is PP blended then you have in the process greater than 40%. The standard is O2 clean. Every one accepts that. This has been taken to the exstreem of 23.5% and >50psi requires O2 cleaning. BTW it started with all sytems no matter what % requires O2 cleaning. That included the fill station at the gas station that filled your tires. It was raised to exclude those systems to 23.5 and 50 psi. This ludicracy is a recommendation that was placed in the national regestry. A federal law exists that says things in this registry is to be considered law. Major buck passing scheme.




---------- Post added June 26th, 2015 at 05:06 PM ----------

The situation you cite could happen However the vis sticker says O2 clean or serviced to 40%. if 40% then no PP blending allowed. O2 cleaning was done to allow PP blending. Even if my LDS does bank fills i have the tanks O2 cleaned for the instance of getting a fill from a PP shop. It is very similar to the hyperfilter air requirements. Agai what the shops call for and the regs require if often diffferent.

What is this national registry?

 

[Mcarlson]

There are two issues that are very separate. One is the danger of dealing with the gas on the surface---fire or explosion while the gas is being handled. The other is the effect on the body, which means the danger of oxygen toxicity to the person breathing it.

This makes sense, but there are several comments about PP blending and the requirement to be O2 clean when that is done. I assume that O2 clean is a reference to the interior parts of the cylinder, which would not be exposed to higher PPO2 from this process.

 

[boulderjohn]

This makes sense, but there are several comments about PP blending and the requirement to be O2 clean when that is done. I assume that O2 clean is a reference to the interior parts of the cylinder, which would not be exposed to higher PPO2 from this process.

PP blending is part of what I meant by the need to be O2 clean on the surface. In that case, it is the fraction of O2 that maters, especially when pure O2 is passing through a valve and into a cylinder, both of which need to be pretty darned clean. If not, you need to use the RLH strategy. (Run Like Hell.)