One issue is, use steel gas lines and no plastic. And take care for the gaskets valves, they must stand a lot of Grays. If they loose their leakproofness you get problems with fire safety.

And of course you ionize the gas in the lines so changing the chemical features. If you take a short shut of gas before applying it to patients, this won´t be a problem. I´ve no formal regulation, just thinking.

I already answered, but my text dissapeared. I´ll try it again. The first point is you should use steel gas lines, because high doses possibbly destroy plastic materials. The second point is, please watch your seels and valves, no plastics again.

You won´t have problems with the gas contents, because before use you cam stream out the first milliliters to clean it from radiation caused chemical modifications.

Hi, thanks for this, I appreciate it! We are using copper pipes. I also thought just bleeding out some gas before use should take care of all the chemistry. If I find out more about medical gas lines in a linac bunker I will post it here...

Like Hanno Krieger, I am not aware of any regulation.  But everything depends on the energy of the Linac beam. We use 18MV and then you have considerable neutron production in the air and metal in the beam path. I do not expect an accumulation in the standings gas volumen (consider the half life time of the fission products)  but  I would expect an raising isotope concentration in the O2 during high energy irradiation (>10MV). Can this radioactivity exceed any regulatory limits? I guess not. For hygenic reasons and because of the rare use (we rearly treat children) we use botteld gas.  An interesting question.  gerd

Good morning, thanks for this reply. It is a high energy bunker (designed for 18 MV), but will only get a 6 MV unit for now. We also use bottled gas, but don't have a dedicated anaesthetist and find it takes very long and severely disrupts the patient list (last year we treated 1506 patients on two linacs and a theratron); so we decided to add gas lines in the new bunker. I have not found anything on regulatory limits either. I guess we'll get some ozone production and the nitrous oxide might break down to form nitrogen dioxide, which might end up going the nitric acid route, but I don't think this will end up a problem clinically. I'm not too worried about the possible neutron activation for a high energy beam, but mostly about the possibility of chemical changes...

Dear Christoph,

take care for Co-59 contaminations of your structures. Using high energy photon beams you will produce neutrons by nuclear photo reactions. These neutrons could be captured by metalls containing natural Cobalt. The result would be 60- Co with the known problems.

For oxygen we normally use SS lines and valves. Mixing  metals will increase probability of corrosion, especially if the gas is not dry. The other concern is potential for self ignition that can occur at the valve if the flow become unstable.