AHU filter maintenance: when to clean, when to replace
A maintenance schedule built on pressure drop instead of the calendar, with checks that keep fan energy and indoor air quality under control.
Gabtic engineering team · · 5 min read
Change on pressure drop, not on dates
Fit a differential pressure gauge across each filter stage. Record the clean (initial) reading at installation, then replace the filter when it reaches the final pressure drop on its datasheet. In dusty seasons that can be twice as fast as in winter, so a fixed calendar either wastes filters or wastes fan energy.
Monthly checks
- Read and log the pressure gauge on every stage.
- Look for gaps between the filter and the frame — bypass air defeats the filter.
- Check bag filters for torn or collapsed pockets.
Cleaning washable filters
Washable synthetic and metal pre-filters can be rinsed with low-pressure water from the clean side to the dirty side, then dried fully before refitting. Never wash bag, pleated or HEPA filters — water and brushing damage the media and the filter loses its class.
Replace the whole stage together
Replacing only the dirtiest filters in a bank creates uneven airflow. Change the full stage, label the date and the initial pressure drop, and keep a spare set on site for each AHU size.