| Dust and pollen filter with activated charcoal filter element: |
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| With the introduction of the air quality sensor -G238- , vehicles fitted with an air quality sensor -G238- are provided with a dust and pollen filter with an additional activated charcoal filter element. |
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| The filter with ACF layer continues to function as a dust and pollen filter, but it is also designed to filter out gaseous pollutants such as ozone, benzene and nitrogen dioxide from the air through-flow. |
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| The purpose of the activated charcoal is to absorb the gaseous pollutants in the air flow until the fresh air flap has closed and the air conditioner is operating in air recirculation mode. Switching from fresh-air to recirculated-air mode is implemented by operating and display unit (Climatronic control unit -J255-) as soon as air quality sensor -G238- detects gaseous pollutants in the ambient atmosphere (“automatic air recirculation” function must have been selected). |
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| The charcoal layer in the dust and pollen filter has a different effect on the various pollutants in the air: |
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| Certain pollutants are permanently bonded in the activated charcoal layer. |
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| Others are converted into harmless compounds as in a catalytic converter. |
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| In all other respects, the activated charcoal acts like a condenser. As noxious substances increase, initially they are stored until a certain level of saturation is achieved. If the pollutant proportion decreases, the activated charcoal layer continuously emits the absorbed particles again. |
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| As the charcoal layer permanently bonds some of the pollutant particles, it is appropriate to renew the dust and pollen filter sooner than prescribed under the following usage conditions: |
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| Vehicle operation in areas with severe air pollution |
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| Vehicle operation with “Automatic air recirculation” function predominantly deactivated |
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| Vehicles with no air quality sensor -G238- as optional extra and thus no “Automatic air recirculation” function |
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| On vehicles with air quality sensor -G238- as optional extra, 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: |
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| Activated charcoal layer in dust and pollen filter becomes saturated after a certain length of time. |
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| A saturated filter can no longer absorb pollutants and allows them to pass unhindered. |
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| The main function of a dust and pollen filter and the air quality sensor -G238- is to prevent peak pollution levels entering the passenger compartment. The following must be observed in doing so: |
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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 the system switches from fresh air mode to air recirculation mode 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, the system always switches from fresh air mode to air recirculation mode if there is an increase in the level of pollutants (e.g. when driving through a cloud of diesel emissions from a lorry). |
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| The activated charcoal filter can be fitted on all vehicles (including vehicles with no air quality sensor -G238- as optional extra). The same restrictions then however apply to these vehicles as when operating the air conditioner with the “Automatic air recirculation” function deactivated. |
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