Should I adjust ventilation rates for high altitude sites?

For high altitude sites like it is sometimes appropriate to apply a correction to ventilation and infiltration rates. Values entered in ach or l/s are translated by the to kg/s on the basis of the air density at sea level. This means that to achieve a given ventilation rate in l/s for high altitude sites you need to reduce the values by the ratio of the air densities, which is (to a good approximation) the same as the ratio of the atmospheric pressures. The site's atmospheric pressure is recorded on the simulation weather file.Having said that, occupants' requirements for mechanical ventilation remain the same at high altitude when expressed in kg/s, so there's a case for keeping mechanical ventilation rates at a nominal 8 l/s (or whatever figure you'd normally use).

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