Air filtration cassette, an air filter and a filter arrangement

An air filtration cassette extending in a length direction between a first end and a second end, related to an intended air flow direction from the first end to the second end during use, the air filtration cassette comprising:

• a filter material disposed between an outer boundary surface and an inner boundary surface, the air filtration cassette having an interior open space encompassed by the inner boundary surface and the filter material, and having an opening arranged at one end of the open space and being closed at the other end thereof,
• wherein the filter material is a bed of air filter media disposed between air permeable structures forming the inner and outer boundary surfaces;
• or a sintered body of granules, spheres or pellets, and
• a distance between said inner boundary surface and said outer boundary surface at said second end is larger than a distance between said inner boundary and said outer boundary at said first end,
• wherein both of said outer boundary surface and said inner boundary surface delimit a cone shape or pyramid shape or a frustum thereof or comprises a number of consecutive sections having the shape of a cone or pyramid or a frustum thereof or the shape of a cylinder or parallelepiped, and said inner boundary surface tapers more toward the second end than said outer boundary surface.