What must be done to interior doors during building preparation according to ASTM E779 - 19?

During building preparation for whole-building airtightness testing in accordance with ASTM E779 - 19, all interior doors must be open. This practice is essential because it allows for an accurate measurement of the building's overall air leakage by ensuring that air can flow freely throughout the space being tested. By having doors open, the pressure differential created by the testing equipment is not impeded, which helps in obtaining reliable data about the airtightness of the building envelope.

Closing, locking, or removing doors would restrict airflow in various parts of the building and potentially lead to false readings during the test. Having doors opened eliminates any confounding factors that might affect the distribution of airflow, allowing the test to result in a true representation of the building's airtightness. This is a critical aspect for achieving valid and trustworthy results in the testing process.