These vent to atmosphere so there is no positive pressure. That is a key point of the design.
Actually there is a small trap to prevent air from entering so the pressure may be 0.5" H2O.
There are guides for these in some of the Hygenic Codes (BPE or EHEDG) but I don't think that they are actually rules.
To my knowledge there isn't a design code for a pressure vessel made entirely of glass. I assume you are asking about a large-scale vessel rather than a lab-scale vessel. I have experience with large glass-lined pressure vessels, but I have never heard of one made entirely of glass - that doesn't sound safe or economical.
Glass-lined pressure vessels are made by a number of manufacturers. The outer metallic shell provides safety and physical strength. ASME Sec VIII Appendix 27 has requirements for this design.
We had a relatively large (20 ft) glass column in my university as a "pilot" lab for educational purposes. I've seen other instances of pilot scale glass columns.
As a pressure vessel though and to specific pressure vessel codes? I don't think that's feasible since glass can't be assigned a pressure rating as far as I know.
