Fresh Air Fractions

摘要

The approach to calculation of outdoor air quantities used in section 2 of AS 1668 part 2 is not easy to use, and creates difficulties for engineers when designing air conditioning systems that serve a group of enclosures. The occupancy of the whole building may be known to be considerably less than the figure obtained by adding occupancy rates for individual enclosures, but AS 1668 does not specify how to factor this diversity into the calculations of required outdoor air quantities. When a small change is made to a large air conditioning system, as occurs for tenancy fitouts in multistorey buildings, the AS 1668 approach requires reference to the outdoor air requirements for all enclosures complicating the task of the design engineer and of regulatory authorities.