Hydrogen is steadily being formed in the atmosphere in various ways while at the same rate it is being lost, so that it is maintained as a “permanent” constituent, amounting to about 1 part in 10,000 by volume in the lower atmosphere, though there is extremely little if any in the upper atmosphere. From geologic times H2 can have been and still be added to the air in many ways, which are listed below. It is being lost by diffusion through the upper atmosphere to space and used up by soil bacteria.

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