What's measured
A filter is meant to clean the air before it is discharged or recirculated, but as it does its job it slowly chokes the system that feeds it. Filter condition is one of the biggest single influences on whether an LEV system passes its test.
The short answer
A filter is meant to clean the air before it is discharged or recirculated, but as it does its job it slowly chokes the system that feeds it. Filter condition is one of the biggest single influences on whether an LEV system passes its thorough examination.
The detail
As dust loads a filter, its resistance rises and the pressure drop across it climbs. If the fan cannot overcome that extra resistance, the total airflow through the system falls, and capture at every hood falls with it. The pressure drop across the filter, read against the value recorded at commissioning, is the clearest single sign of how loaded it is - and the signal that tells you when it needs cleaning or replacing, rather than guessing from the calendar.
The opposite failure matters just as much. A damaged, split or wrongly fitted filter lets contaminant pass straight through instead of catching it. That is dangerous on any system, and far more so on one that recirculates the cleaned air back into the workplace, where a breached filter feeds the dust it was fitted to remove directly back to the people it was meant to protect. On a system ducted to atmosphere the same breach simply vents the dust outside, which still fails the test but carries a different risk.
What it means for you
At test the examiner measures the pressure drop across the filter and compares it to the commissioning figure, checks the media and seals for damage and bypass, and confirms that any cleaning mechanism - a reverse-jet or shaker system - is working. A blinded filter that no longer cleans, or a cleaning cycle that has stopped firing, shows as a pressure drop that has climbed and stayed high. A filter left in too long throttles the whole system; a filter breached releases the very dust it exists to catch. Both show up in a proper examination, and both are easy to miss without one.
Timely attention, guided by the pressure reading rather than a fixed schedule, keeps airflow where it should be and keeps the discharge clean. The filter is not a fit-and-forget component - it is a consumable whose condition the whole system depends on. Left unchecked, a slowly loading filter can pull a system that passed comfortably at its last test below the required airflow well before the next test is due.
The service behind the guide
We measure the pressure drop across your filters against the commissioned value and check the media and seals for damage and bypass, with a clear report and remedial actions.
Questions
As dust loads a filter its resistance rises and the pressure drop across it climbs. If the fan cannot overcome that resistance, total airflow falls and capture at every hood falls with it.
The pressure drop across the filter, read against the value recorded at commissioning, is the clearest sign of loading. It tells you when to clean or replace it rather than guessing from a schedule.
A split or wrongly fitted filter lets contaminant pass straight through. That is especially serious on a recirculating system, where the breached filter feeds dust straight back into the workplace air.
The pressure drop across the filter against the commissioned figure, the media and seals for damage or bypass, and whether any cleaning mechanism such as a reverse-jet or shaker system is working.
Yes. A heavily loaded filter can pull airflow below the required level across the whole system, and a breached one fails on contaminant release, so filter condition often decides pass or fail.
Phoenix Duct Clean · by the numbers
We measure the pressure drop across your filters against the commissioned value and check the media for damage and bypass, with a clear report.