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I need to measure the concentrarion of pure hydrogen in a room caused by leakage or exhaust gases to evaluate the risk of ignition. Maybe there is some model available for indoor locations, similar to the Gaussian plume model for gas dispersion.

The density of hydrogen is very low compared to air, buoyancy is high and diffusion is high. So the diffusion formula for other gases may not work for hydrogen.

Does somebody know a formula, method or reference to calculate the concentration of hydrogen in a room?

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    $\begingroup$ One or both of Fick's laws should do the trick. $\endgroup$
    – Todd Minehardt
    Commented Mar 1, 2022 at 15:58
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    $\begingroup$ Diffusion is simple. Otherwise you won't get away without full 3D flow modelling of your room. $\endgroup$
    – Karl
    Commented Mar 1, 2022 at 18:46
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    $\begingroup$ Diffusion is too simple for this case? I'm not familiar with a full 3D flow model. Is it correct that that model should include the shape of the ceiling, the HVAC pipes at the ceiling, the air flows, open windows and objects around the room? $\endgroup$
    – Mark Houlen
    Commented Mar 2, 2022 at 10:46
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    $\begingroup$ What such model is, is impossible. No way to tell what happens if someone leaves a door open in the end of corridor, or day is very windy. $\endgroup$
    – Mithoron
    Commented Mar 2, 2022 at 18:30
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    $\begingroup$ First you should decide if buoyancy is relevant for your problem. Then you install a ventilation system, and close the case. $\endgroup$
    – Karl
    Commented Mar 2, 2022 at 19:01

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Hydrogen rises to the high points; not "pure", mixed with air so there is a high risk of ignition. So, those who work with hydrogen risk plan for it, they do not calculate possible concentrations. Explosion proof lights and other electrical devices are used. Also exhaust ventilation. Some organization like Underwriters Labs will have recommendations. All I know is when I designed a lab to work with hydrogen , the company safety department increased the estimated costs with various precautions.

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  • $\begingroup$ Quite interesting that you designed a lab to work with hydrogen. With explosion proof lights do you mean hydrogen concentration meters around the lab? Was the exhaust ventilation local over the hydrogen devices and/or global on the room? $\endgroup$
    – Mark Houlen
    Commented Mar 1, 2022 at 16:51
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    $\begingroup$ The testing was for high temperature hydrogen attack of steel. There was both hoods over test equipment and room ventilation. The safety group did all the design so I do not know exactly what they did. I do not recall any hydrogen test meters in the room. $\endgroup$
    – blacksmith37
    Commented Mar 1, 2022 at 21:53
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    $\begingroup$ Look up Class 1 Div 1 equipment. Specifically for potentially explosive atmosphere. $\endgroup$
    – Jon Custer
    Commented Mar 2, 2022 at 13:36

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