A variable air resistant filter 100 (intended to filter any or a combination of air, dust, and sand), and a mask incorporating such a filter, comprises a first component 102 that is configured as a filter top and includes one or more air inlet apertures 104, a second component 106 that is configured as a main body of the air filter and detachably coupled with the first component and a third component 108 that is configured as a filter holder (for holding, for example a polyester material capable of filtration) and is detachably coupled with the third component. The first component may include an opening 110 in its centre which aligns with and is engaged with a protrusion 112 in the second component. The first component may also be constructed in two layers； a first (top) layer (114, Fig 2A) having one or more air inlet apertures and a second (bottom) layer (116, Fig 2A) for supporting the first layer.
