To meet the requirements of ASHRAE Standard 62, you must demonstrate that you are either providing the amount of fresh ventilation air specified in Table 2 of the standard, or that you have effectively controlled contaminant sources by the methods described in the standard. Although the standard implies that it is possible to achieve this result with natural ventilation, these results must be demonstrated. One way to achieve this might be to develop a tracer-gas test (described in ASHRAE 55-1999) to demonstrate that the natural ventilation system you have designed performs effectively to meet the requirements. You might also develop engineering calculations of natural ventilation based on wind pressure and thermal buoyancy (stack-effect) driven ventilation. These calculations are described in ASHRAE Handbook of Fundamentals, Chapter 22. The new version of ASHRAE Standard 62, released in 2001 also contains a calculation methodolgy for natural ventilation that may be simpler to use than other methods. The intent of this prerequisite is to meet the requirements of ASHRAE 62. This determination is not made based on a building owner\'s satisfaction with apparent ventilation performance in similar facilities. The prerequisite would not be met without some basis for determining that the project meets the requirements of ASHRAE Standard 62. Applicable Internationally.