In an effort to home in on your question more, I ask the following. I might not have the answer but those who do may appreciate a little more clarity.
Will the hydrogen be in trace amounts in the surrounding air or are you trying to measure it in a container to determine its concentration.
By the way, in the past they used to put some gas that smells with the hydrogen so that you know you have a leak by smell alone. They still do this with natural gas.
FYI – hydrogen will burn or explode in the concentrations range of about 5% to 85% in air, which is a very big range.