August 2023 update addresses some changes in the guidance how to calculate the point source ventilation effectiveness. These changes are in the explanations of Equations 5 and 6, and in the calculation example in Appendix 3. It is noted that ventilation effectiveness should be calculated from average concentration at the breathing level, and if local air quality index values are used, the reciprocal values are to be summed as shown in new Equation 23.

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