| Notes on dust and pollen filter with activated charcoal filter element |
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| There are different versions of the dust and pollen filter without and with activated charcoal filter element → Electronic parts catalogue. Vehicles with an air conditioner of the „Deluxe“ type are currently fitted with a dust and pollen filter with an activated charcoal filter element, whereas vehicles with an air conditioner of the „Basic“ type have a dust and pollen filter with no activated charcoal element. |
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| In Model Year 2012, a modified dust and pollen filter with ACF element is to be gradually introduced on vehicles with an air conditioner of the „Deluxe“ type. This filter with an enhanced fine dust separation rate has roughly the same air resistance values as the filter fitted prior to conversion and can thus also be installed on vehicles manufactured prior to conversion → Electronic parts catalogue. |
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| The dust and pollen filter with additional activated charcoal filter element is fitted on vehicles with an air conditioner of the „Deluxe“ type. Such vehicles are also fitted with an air quality sensor -G238- → Chapter. |
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| The filter with activated charcoal element acts as a dust and pollen filter. It can however also filter gaseous pollutants such as ozone, benzene and nitrogen dioxide out of the flow of air. The principal function of the activated charcoal layer in the dust and pollen filter is to prevent peak pollution levels entering the passenger compartment. |
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| A further function of the activated charcoal is to absorb certain gaseous pollutants in the air flow. The activated charcoal layer in the dust and pollen filter has a different effect on the various pollutants in the air: |
| - Certain pollutants are bonded in the activated charcoal layer. |
| - Others are converted into harmless compounds as in a catalytic converter. |
| - Otherwise, the activated charcoal acts as a condenser. As the impact level increases, pollutants are initially absorbed until a certain degree of saturation is attained. If the pollutant level drops, the activated charcoal layer continuously emits these absorbed particles again. |
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| As the activated charcoal layer permanently bonds some of the gaseous pollutant particles in addition to dust and pollen, it is appropriate to replace the dust and pollen filter sooner than prescribed under the following usage conditions: |
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| Vehicle operation in areas with constant severe air pollution. The activated charcoal layer in the dust and pollen filter becomes saturated sooner than specified. |
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| Vehicle operation with the „Automatic air recirculation“ function predominantly deactivated. |
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| On vehicles with an air quality sensor -G238-, the air conditioner should be operated as far as possible in „automatic air recirculation“ mode. Should it however be necessary or desirable to deactivate the function, attention must be paid to the following: |
| - The activated charcoal layer in the dust and pollen filter becomes saturated after a certain length of time. |
| - A saturated filter can no longer absorb pollutants and allows them to pass unhindered. |
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| The main function of the activated charcoal layer of the dust and pollen filter and the air quality sensor -G238- is to prevent peak pollution levels entering the passenger compartment. The following must however be heeded: |
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| If a vehicle is driven in an area with a relatively clean environment (with few gaseous pollutants in the air), the point at which switching from fresh-air to air recirculation mode takes place is different to that in areas with a high basic impact level (e.g. industrial estates). |
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| Irrespective of the basic impact level, switching from fresh air to air recirculation mode always takes place if there is an increase in pollutant level (e.g. on driving through a cloud of diesel emissions from a lorry). |
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