Hydrogen gas (the part of BG that is combustible) needs to be at least 4% in air by volume before it is combustible.
Hydrogen rises VERY fast and diffuses in air VERY fast, so even a minimal ventilation would prevent a combustible mixture from forming in the room.
Let’s do some math. A 3 meter cube (a small room) contains 27,000 liters of space. 4% of 27,000 is 1,080 liters.
Assuming your electrolyzer makes 50 liters of hydrogen per hour, there would be (at least) 20 hours of continous use before a combustible mixture could form.
BUT: Hydrogen is a very tiny molecule and can fit through the smallest of cracks (it even travels through metals). So it is almost impossible to contain in a room that has ANY ventilation. Just opening a door once in awhile will ventilate a room enough to prevent a combustible mixture.
And this doesn’t take into account if a person is breathing the BG, so some of the hydrogen is being ‘consumed’ by the breather(s); just like oxygen is a room is consumed by breather(s).
So, for practicality, just assume that if the room is ventilated well enough so that the breather(s) have enough fresh oxygen to breathe, that there can NEVER be a combustible mixture in the room (from an electrolyzer producing such small quantities of hydrogen).
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