ANSI/ASHRAE Standard 62, Ventilation for Acceptable IndoorjAir Quality,1 has been modified by Addendum 62n2, whoseventilation requirements alter the very heart of Standard 62.Addendum 62n contains a long-awaited update to the minimumprescribed ventilation rates — last updated in ASHRAE Standard62-1989 — and it incorporates ventilation airflow “additivity” fordilution of both people-source and building-source contaminants.The updated version of the once-familiar table of prescribedbreathing-zone ventilation rates now contains both per-personand per-unit-area values for each occupancy category.