Just to give you some back ground. I've been an installer for 15 years and have recently changed jobs to become an inspector and plan reviewer for Memphis and Shelby county. The reason this has come up is I recently inspected a pain clinic and it had oxygen for nerve block procedures. I ask them for a risk assessment. And they said they would be category 2. This was in a multi tenant multi story building. The installer asked if he had to terminate the relief valve outside because the only way with out running it through a bunch of tenants was for him to hire someone to drill the glass windows. I told him yes but did a lot of searching through the code and noticed that all the dental offices had manifolds with relief valves that discharged in the manifold room. So I started really searching for an allowance for that. I could be wrong but I can't find it. I see where "air" can but not gases. I was wondering if the manufactures got it wrong or if the "air" should of been gases with the exception of making the room oxygen deficient. I asked the staff at the NFPA and they sent me the section 184.108.40.206.7 of the 2012 and 220.127.116.11.1.4 of the 2015. Which the 2012 section says "air" and the other says "dental air". Which dental air is defined in the 2018 as pressurized cylinders of air, compressed air systems, nitrogen and CO2. I wrote him back about the "air" and have not received a response. I hate I paid for a membership. Really I was asking for intent. I don't really care if the code is not written exactly right as long as I know what to enforce. I think you are probably right about everything but I don't see where the code states it. It would be nice if the NFPA staff would email me back stating that the "air" was meant to include NO2 and O2. As far as the exhaust I had an engineer send me the section in chapter 11 stating that he didn't have to provide exhaust because you only had to when more than 3,000 cu. ft. was stored. At the time my under standing was chapter 11 was for all cylinder storage. So I made him provide it per the Mechanical code. Which requires makeup air and exhaust to the outside in a 1hr. enclosure but, only requires 50 CFM. That is the other part of the exhaust that the NFPA is not clear about. Because the gas has to be in a 1hr. enclosure the duct men want to install dampers on the exhaust and make up air if provide. And it seems like the system should operate during a fire. And its hard to make the system comply with both codes. After that wondering about the ventilation and reliefs I noticed the same requirement in section 18.104.22.168.2. Part of the question was because of all dental offices with piped medical gas system will now be category 2 and I was wondering if this would make the manifolds change per section 22.214.171.124 of the 2018. I would really appreciate anything you could add.