According to ASTM E1258, how should fans be calibrated?

Fans should be calibrated at 6 differently specified pressure points as specified by ASTM E1258. This approach ensures that the fan’s performance is accurately characterized across a range of operating conditions. The calibration at these pressure points helps in evaluating the fan's ability to maintain consistent airflow and pressure levels, which are crucial for accurate whole-building airtightness testing.

This method allows for a comprehensive assessment of fan performance, as it accounts for variations that might occur in real-world applications. By calibrating at multiple pressure points, testers can better understand the efficiency and reliability of the fan under different conditions, leading to more reliable testing results. Moreover, this calibration process provides data that can be used to adjust testing methods and improve the accuracy of airtightness measurements.

Considering other options, calibrating at a specific height above ground lacks the comprehensive analysis needed for the variable nature of real-world scenarios. Testing under varying humidity conditions or only at room temperature does not address the necessary breadth of performance characteristics that must be evaluated in the calibration process. Thus, calibration at multiple pressure points is essential for ensuring accurate and reliable airtightness test outcomes.