This tool helps maintenance engineers rapidly verify whether increasing HVAC airflow to meet a new cleanroom class requirement will push existing HEPA housings beyond their mechanical static limits.
Applies the industry-standard linear scaling law dP_op = dP_nom × (Q_op / Q_nom) to predict clean media resistance under variable fan speeds without consulting bulky manufacturer curves.
Q: Is this calculation valid for dirty or loaded HEPA filters?
A: No. This tool applies strictly to clean, undegraded filter media. As filters capture particulates, resistance increases independently of airflow; always rely on live manometer readings during scheduled maintenance checks for loaded units.
Q: Why does this calculator require US Imperial units instead of metric?
A: US cleanroom standards (ISO 14644-1 adopted by ANSI) and ASHRAE ventilation guidelines predominantly specify Imperial units. Multiply CFM by 0.47196 for L/s, or 0.028317 for m³/h before entering values if your local datasheets use metric units.
Q: How does the pressure drop change if I reduce the system airflow significantly?
A: Under the linear assumption, reducing flow proportionally lowers the clean pressure drop, easing static head requirements on the supply fan. Always verify the reduced velocity still satisfies minimum flush-air volume codes for your target ISO class.
Q: Can I use this output to approve a fan speed increase?
A: It provides a quick baseline for clean-media resistance, but final approval must account for frame bypass leakage, gasket compression, and seal degradation. Once you confirm the static load is safe, run the numbers through our cleanroom-unidirectional-airflow-velocity-calculator to ensure terminal velocity meets contamination control targets.