What are the two key pieces of equipment necessary during the air tightness test?

The correct choice highlights the necessity of fans and pressure tubing during an air tightness test. Fans are crucial because they create the airflow needed to either pressurize or depressurize a building, which allows for the measurement of leakage rates through the building's envelope. The pressure tubing plays a significant role in establishing and measuring the pressure differential that is created by the fans.

When the fans operate, they change the pressure inside the building, and the pressure tubing connects to a manometer or pressure gauge, enabling accurate readings of the pressure conditions. This data is essential for calculating the air leakage rate, which is the fundamental outcome of the airtightness test.

Other options, while they contain important components related to the testing process, do not encompass the two critical elements required for conducting the test effectively. For instance, sensors and monitoring devices are useful for observing conditions but do not directly create the airflow necessary for the test. Similarly, computers and software can be valuable for analyzing and storing data post-testing but are not intrinsic to the immediate physical process of creating and measuring airflow across the building envelope.