Filter Performance
Pall's decades of design and manufacturing expertise ensures the following:
- C check filter element service life (result of high dirt holding capacity)
- Minimum pressure loss
- Minimum weight
- High collapse strength
- True HEPA filters (>99.999% microbial removal efficiency)
- High adsorption capacity for odors/VOCs (with optional carbon filters)
A poorly designed cabin air filter, e.g. with low collapse strength and low dirt holding capacity, could rupture in service causing contaminants to be released into the cabin.
This type of failure will NOT be detected by monitoring the filter element pressure loss because a ruptured cabin air filter will NOT cause a high delta-P indication.
View the list of Pall's next generation of cabin air filters
Filter Test Facilities
To ensure the filter performance meets OEM and/or customer specifications, Pall conducts extensive testing in their own laboratory facilities.
For air filter testing and qualification, the laboratory equipment includes:-
- Suction Rigs (i.e. wind tunnels)
- High pressure flow equipment
- Filter Efficiency test rigs (sodium flame or cold PAO DOP)
- Adsorption technologies
- Temperature fatigue test equipment
- VOC challenge equipment
- Other specialised test equipment
This enables the following cabin air filter tests to be performed in-house
- Air flow pressure loss - to BS1042 or ISO5167
- Filter efficiency, life & dirt holding capacity to ISO5011
- Sodium flame test to EN1822-1
- DOP test to MIL- STD- 282
- Collapse testing
- VOC removal testing
- Flow distortion
- Filter effluent characterisation
Filter Efficiency Testing
There are a number of international standards for measuring air filtration efficiency.
To be meaningful, the reported efficiency must state the particle challenge size and flow velocity used during the test.
According to ASHRAE Standard 161-2007 (Section 6.3.1)
"All air that is recirculated through the aircraft systems shall pass through a high efficiency particulate air (HEPA) filter before it is supplied to the cabin. HEPA filters used for this purpose shall meet or exceed the requirements of Institute of Environmental Science and Technology IEST-RP-CC007.2 Filter Type "A," or MERV 17 or H13 according to EN 1822-1, and shall provide a minimum of 99.97% collection efficiency for 0.3 micron particles.
Alternative technology may be used to meet this requirement if it provides the same removal efficiency as required above for HEPA filters and is so demonstrated by a test method approved by a cognizant authority"IEST = Institute of Environmental Science and Technology
ISO standard EN1822-1 (Europe)
This standard applies to high efficiency particulate and ultra low penetration air filters (HEPA and ULPA) used in the field of ventilation and air conditioning.
For aircraft cabin air recirculation systems, Airbus specifies HEPA filters greater than 99.99% removal efficiency by sodium chloride test.
This test consists of challenging the filter with an aerosol of sodium chloride (NaCl) particles, with a mean particle size of 0.58 micrometres. The removal efficiency, or penetration are calculated as a percentage by measuring the aerosol concentration upstream and downstream of the filter element under test.
MIL-STD-282 (the Americas)
For aircraft cabin air recirculation systems, Boeing specifies that the minimum filter efficiency shall be 99.97 % at the rated flow specified for each filter to be measured by MIL- STD- 282 Method 102.9.1, DOP Filter Efficiency Rating which uses dioctyl phthalate at a uniform diameter of 0.3 micrometer
The removal efficiency, or penetration are calculated as a percentage by measuring the aerosol concentration upstream and downstream of the filter element under test.
Air Filter Efficiency Testing - Sodium Chloride Flame Test Rig
Filter Life Testing
The filters are challenged with a variety of contaminants, including, for example ISO fine, ASHRAE test dust and Airbus test dust.
This ensures the cabin air filter design will maintain a low differential pressure under the most challenging conditions. The differential pressure build up across the filter is monitored until the test reaches a pre-determined level (the "terminal delta-P") then the test is stopped.
Pall's laboratory support services have been used by airlines around the world to monitor the in-service performance of their cabin air filters.
Tests on used cabin air filters have proven filter service life on some applications in excess of 6000 flying hours.
Note: There is no definitive time interval for changing out a cabin air filter element. The time interval varies between aircraft types. Pall recommends that airlines follow the guidelines provided by the manufacturers in the aircraft maintenance manuals (AMM's).
Test Rig for Dust Life Testing
