Atmospheric Pressure and Its Effects on Rate of Diffusion- Pressure exerted on a gas is usually atmospheric pressure. Atmospheric pressure is measured on a barometer. A rise in the barometric reading indicates an increase in pressure. A drop in barometric reading indicates a decrease in pressure. The atmospheric pressure varies within a mine, just as it does on the surface.
Atmospheric pressure affects the diffusion rate of a gas.
For example, if the barometer rises, indicating increased pressure, gas responds by contracting. A gas that 9 s squeezed into a smaller area like this is more concentrated, so it diffuses more slowly. As you might guess, it s much easier for concentrations of explosive gases to build up when the barometric pressure is high. And it is harder to disperse the gases by means of the mine s ventilation system. On the other hand, when barometric pressure falls, the pressure on the gas is reduced.