SAFETY / How can it be safe to use a mix of 5% hydrogen in nitrogen when the Lower Explosion Limit (LEL) for hydrogen is 4%?
It is the nitrogen that does the trick. No combustion can take place without oxygen. The 4% limit refers to hydrogen in air which contains oxygen. When the 5% hydrogen/nitrogen mix is released into the air it dilutes the air. No matter how much you release, there will either be too little hydrogen or too little oxygen to allow the gas to ignite. Any mix of hydrogen and nitrogen containing less than 5.7% hydrogen is classified as a non-flammable gas. The safety margin is actually greater than that. Even a 10% hydrogen/nitrogen mix is extremely difficult (but not impossible) to ignite.
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