There have been a few comments by hopeful do it yourselfers who want to store up HHO gas in an old propane tank, etc. This is normally not done for a variety of reasons, and some of the biggest concerns are safety. Here is one comment we received:

The only way that I thought of possibly pressurizing the HHO would be to have the entire system pressurized. So that when the HHO bubbles are made it automatically pressurizes the tank. Then when its at the pressure you desire turn the valve to off and bleed the cell to unpressurize it to add more water or do maintenance. The highest pressure you could probably achieve is about 35-40 PSI without spending a ridiculous amount of money on expensive equipment. The tanks they are using for Hydrogen prototype cars have a cap at about 10,000 PSI But those tanks alone are about $5,000. The main problem here is pressurizing the HHO cell and lines without leaks or explosion.
From what ive seen online people seem to be yielding about 2liters per minute off their HHO cell and receive about 25% increase in efficiency. Wouldn’t you then be able to run your vehicle completly off of 5 HHO cells running simultaneously?

Ok, so here’s a few things to consider. Hydrogen weakens normal metals and materials. This leads to cracks and leaks. A lot of research was done by accredited labs, etc on hydrogen storage years ago. My understanding of the matter is that high pressure hydrogen will find a leak if even the smallest pinhole is present, and escape to atmosphere. Or, escape to the trunk and interior of your car! Also, the average home built unit will have trouble holding much pressure and the gas will start causing small leaks in your system.

Also, HHO is an explosive mixture of hydrogen and oxygen which no sane person would try to store in a jury rigged homemade container in their vehicle. It’s flat out dangerous. Most gases that are stored need oxygen to mix with them to make them burn, ie. propane. The mixing is already done with HHO generators, and this is why sometimes you can have a flashback to your production unit. If you have a little flashback and ruin your generator, that is one thing. How about packing a bomb around in your trunk? Those storage tanks mentioned are for pure hydrogen, which none of us are making with our simple generators.

The best bet in my opinion is to produce the HHO gas and burn it right away as needed in your engine. Never have your hydrogen generator running with the ignition off. Use a flashback arrestor on any high production unit. And always experiment in a well ventilated area when testing your new unit. You don’t want to take any chances.

If you must store hydrogen, you need to have ALL STAINLESS STEEL fittings. You need to use a stainless steel tank. Better yet, an expensive but safe metal hydride tank which will store the hydrogen gas in a solid form. Remember, a regular pressure pump might not have high quality stainless steel insides or corrosion resistant parts unless it is specifically built to handle acid or hydrogen. This goes for most valves, regulators or other parts you might think would work in a pressurized system.