There are two types of cabin filters (or pollen filters) at Cairfil - the standard filter (SF) and the activated carbon filter (ACF), also known as the combination filter.

Standard Filter (SF)
The standard filter absorbs primarily solid particles like industrial dust, pollens, fungus spores, and bacteria from the external air. This can be realized by using a specially developed filter medium.

Activated Carbon Filter
Activated carbon filter also known as combination filter. In addition to solid particles, the activated carbon filter filters harmful gases like nitrogen oxides, sulfur dioxide, ozone and hydrocarbons, removing about 95% of these from the air reaching the passenger compartment: the smallest particles are filtered and adsorbed by the embedded layer of activated carbon.

Likewise, unpleasant odours are adsorbed, reducing the oppressive smells often experienced when driving in tunnels or in traffic jam situations.



The activated carbon filter consists of various media arranged in layers: a carrier medium, which gives the filter more mechanical stability, a filter medium and an activated carbon layer.

Filteration principle

 

 

The filtration principle of an activated carbon filter is fairly straightforward and is represented schematically in the diagram at the right: When air passes through, the filter medium retains the solid materials, while the activated carbon layer binds gases and odours.

 

The activated carbon filter is a better alternative to the standard filter. Therefore, vehicles previously equipped with a normal standard filter can be retrofitted with activated carbon filter of the same geometry without difficulty. Due to its more comprehensive filtering action, increasing numbers of vehicles nowadays have an activated carbon filter as part of the standard equipment.

ZOOM- IN VIEW

 

FILTER SIDE VIEW
 

Filter Medium / Activated Carbon

Activated carbon is a pure, natural product produced from wood, peat, coal, or coconut shells. The porous structure characterizing this mechanical filter develops during the activation process. During carbonization of the raw materials, many small pores are created, which are clogged with tar-like substances. High temperature steam (500 to 800 °C) is used to volatilize these tars, freeing the pores and also enlarging them.

 

This porous surface offers a much higher surface area for filtering than comparable materials (approximately 1000m2 per gram of activated carbon). For the cabin filter or pollen filter, only activated carbon from coconut shells is used, because of its particular mechanical stability and resistance to abrasion.

 

The following illustration shows a cross section of an activated carbon filter under a microscope; in the detailed view, both the active carbon grain and its surface form can be seen.

 

Filter Type Summary Table

Table below shows the filter type, feature and the effective filtration on the contaminants.

MEDIUM TYPE
Contaminant / Feature	Particle filter	Activated Carbon type
Pollen, Dirt and Dust
Dirt and Dust
Soot
Fungus Spores
Electrostatic Charges medium
Odours
Exhaust Gases
Ozone
Anti Bacteria medium