FOREWORD There is confusion in the industry regarding where ventilation system airflow measurements can be taken. This addendum provides guidance on this topic while aligning the language with the latest draft of BSR/RESNET/ICC 380@ Standard for Testing Airtightness of Building Enclosures@ Airtightness of Heating and Cooling Air Distribution Systems@ and Airflow of Mechanical Ventilation Systems@ which is expected to be finalized as an ANSI standard in the near future. Note: In this addendum@ changes to the current standard are indicated in the text by underlining (for additions) and strikethrough (for deletions) unless the instructions specifically mention some other means of indicating the changes.