As can be seen by reaction 2 on the previous page, hydrogen gas is also produced at the cathode. Hydrogen is generated at the rate of 18.656 moles per 1000 Amps/hr.

I mole of H2 = 2.0158g. 18.656 moles H2= 37.606764 g
H2 Gas density = 0.0898 g/1 at 0°C at 1 atm

Volumetric measurements of H2 can be calculated by: V= Vo 273+t Po / 273 P

Where
t=temp in °C
Po, P = pressure in atm
273 = temperature in 0Kelvin relating to 0°C.

Assuming an ambient temperature of 25°C and atmospheric pressure, 
the volume generated by 1,000Alhr is:
273+25 x 418.83= 457.18 litres/hr
273

Hydrogen air mixtures can be hazardous in a wide range of hydrogen/air ratios:
Hydrogen/Air content % volume (25°C)
0 - 4 Not flammable
4- 18 Flammable
18 - 59 Detonative
59 - 75 Flammable
75 - 100 Not flammable

In water, hydrogen oxygen mixtures do not ignite. However care must be taken in ensuring that hydrogen levels do not build up in air or piping to flammable levels. Accordingly, the SAL plant design and installation incorporates the following design factors:

a) Cell and plumbing design to avoid the accumulation of gas build.
b) Automatic cessation of power supply ( and generation of hydrogen) in the event of interruption of water flow.
c) Well ventilated rooms for electrolytic cells.
d) Incorporation of gas loop in plumbing as a secondary preventative measure to avoid continuation of electrolysis in the event of interrupted water flow.
e) Straight line plumbing after electrolytic cells. Placement of cells after receptacles such as filters tanks etc.
f) Strategic venting of hydrogen to the atmosphere on larger units