We had a situation arise recently during a certification inspection on a new dental facility. The situation involved the design team, the facility owners, the county plumbing inspector, and us. The issue was about the necessity of running the pressure relief valves for the O2 and N2O outside of the building. I and my team poured through the NFPA 99, 2021 (this particular county adopted 2021 a couple of years ago, ahead of the rest of the state) Chapter 15 to ensure that none of us were missing anything, but we found that a category 1 dental facility has the following requirement:

15.3.2.1.4 Central Supply Systems: Category 1 systems shall comply with 5.1.3.5 

If we look at 5.1.3.5, especially in 5.1.3.5.6.1(4) (talking about relief valves), it states, "They shall be vented to the outside of the building, except that relief valves for compressed air systems having less than 84,950 L (3000 ft3) at STP shall be permitted to be diffused locally by means that will not restrict the flow."

The problem that we have is that this is a Category 2 Dental facility though! If we look at the requirements for Category 2 in 15.4.2.5.5 and 15.4.2.5.6, it doesn't have any requirement to have the relief valves vented to the outside of the building. There is no reference to comply with Chapter 5 either. 

My question is, why not? We are talking about the same gases (Oxygen and Nitrous Oxide), the same volume, and the same issues of potential explosion hazards and even asphyxiation hazards if enough N2O is released. We referenced 15.2: Nature of Hazards of Gas and Vacuum Systems: "Potential fire and explosion hazards associated with positive-pressure dental gas systems and vacuum systems SHALL be considered in the design, installation, testing, operation, and maintenance of these systems". in our response to the design team and facility owner's objections to paying for 8' of 1/2" pipe being ran. Does anyone have any other references to help combat the usual cheap is better than safe mentality we see too often within the dental world?

Thanks in advance for your consideration!