Depends on your equipment.
FIRST:Brown’s Gas (BG) is powerfully explosive as it is mostly diatomic hydrogen and oxygen in ideal stoichiometric mixture.
As pressure is increased on BG, the gas density increases and its ‘explosion pressure spike’ becomes more powerful.
In my experience:At ambient pressure a ‘torpedo’ type pop bottle will usually contain the explosion; though it will melt from the resulting heat. ‘Static pressure’ tests of torpedo pop bottles show they will withstand about 150 psi. (click)At 70 psi a BG explosion will cause 1/4″ steel plate to become convex. That test was one of the loudest explosions I’d ever heard. I’ve worked with explosives all my life and I have blasting certification.If the explosion ruptures your container, the result is a very powerful bomb.
If the explosion does not rupture your container, you will end up with a vacuum in the container as the BG converts to water, a reduction in volume of 1866 times. It won’t be a perfect vacuum because steam and water vapor take up some volume.
My ER1200 WaterTorches have a 1/4″ steel tube-shell and 1/2″ steel endplates. I operate them at 10 psig. 10 psi is enough to reliably fuel a torch that handles 1200 liters per hour of BG. Lower pressure is safer!
My ER50 electrolyzer is schedule 40 PVC and operates at ambient pressure, or up to 1 psig when operating as a WaterTorch.
SECOND: BG contains all the energy it needs to ignite itself. It only needs a combination of temperature, pressure, and/or a sharp point or edge (to concentrate the ‘static’ electricity).
I once had an ER1150 WaterTorch come all the way back from Australia because, during manufacture, a tiny spiral of metal fell into its liquid/vapor separator.
The WaterTorch passed all our factory tests but upon reaching the customer it would internally explode every time its pressure rose to about 15 psi. (The ER1150 normal operation pressure was about 20 psi).
Upon receiving the WaterTorch back in my lab I confirmed that it was exploding everytime it reached about 15 psi. I took the machine apart, discovered the tiny metal spiral, put the machine back together and it pressurized normally from then on.
I assume that during our initial factory tests the metal spiral was laying point down. As the machine was jostled during transport, the point came up. The sharp point was all the BG needed to self ignite.
THIRD:As I stated above, pressure and temperature are also enough to ignite the BG. The pressure / temperature relationship is inverse. The lower you can keep the temperature, the higher you can pressurize the BG. Personally I like to run my BG electrolyzers hot, so I keep as low a pressure as practical.
I do not have charts on the pressure / temperature relationship because I discovered that, for safeties sake, I never wanted to have high pressure BG anyway.
I do not recommend any application that isn’t thoroughly designed to handle the inevitable internal explosions. Personally I do not pressurize BG… I use it as soon as possible after it is created.
Depends on your equipment.