ISO 29461-2 is the first international standard for reporting an air intake filter's endurance in fog and mist environments, as well as its resistance to water penetration.
Using the data provided by ISO 29461-2, turbomachinery operators have the information needed to select the filter that would perform the best in wet environments.
ISO 29461-2 requires filters to be measured and rated according to the following test parameters:
A filter passes the fog & mist endurance test if it meets criteria 1-3. A filter is considered as ”hydrophobic” If meets all 4 criteria.
When selecting filters, it is important to consider both the ISO 29461-1 efficiency standard and the ISO 29461-1:2 hydrophobicity standard. For most applications exposed to heavy water concentrations, Camfil recommends final filters that are high efficiency T10+ according to ISO 29461-1:2021 and hydrophobic with a low and stable pressure drop according to ISO 29461-2:2022.
The graph and table below shows the importance of considering both standards. All filters are equivalent in efficiency, however, Filters A, B, and C failed either by water bypass, pressure drop or both. Filter D passed the fog endurance test, however, the water dye test showed water droplets downstream of the filter, whereas Filter E showed no bypass. The results show that Filter E would perform the best in high humidity, fog conditions.
Graph: Fog & Mist Endurance Test Final Filter Comparison
Table: Fog & Mist Endurance and Water Dye Test Final Filter Comparison
|Test Duration (min)
||Water Sprayed (liters)
||Water Bypass (liters)
||Max. dP During Test (inch w.g. / pascal)||Pass or
|Optional dye test for water droplets: Is the filter hydrophobic?
|Filter A T10||35
|Filter B T10||65||18||14||4.0 / 1000||Fail||-|
|Filter C T10||180||74||20||2.9 / 720||Fail||-|
|Filter D T10||180||76.5||0||2.6 / 645||Pass||No|
|Filter E T10||180||76.5||0||1.2 / 300||Pass||Yes|
Image: Water Dye Test