A significant feature of the standard is the replacement of the conventional air changes per hour (ACH) metric with the newly introduced "equivalent outdoor air for infection control" (EOAi). EOAi measures the equivalent flow rate of clean air per individual that, when evenly dispersed within their breathing area, would produce the same outcome as a specific removal or inactivation method on infectious aerosols. The standard also highlights the crucial role of Breathing Zones and Air Flow Direction in the efficient operation of air purifier devices.