| abstract |
An air filtration device (1) comprising: a housing (3) having an air inlet (5) and an air outlet (7); air displacement means (9) for displacing air from the inlet (5) to the outlet (7) in a direction D through a filter element (11), the filter element (11) comprising at least one filter unit (13) comprising an absorbent, fibrous material which is impregnated with an aqueous solution of an acid or a base. In a particular embodiment, the filter element comprises two filter units (13,15) in series arrangement, one (15) of which is impregnated with an aqueous solution of an acid and the other (13) of which is impregnated with an aqueous solution of a base. If so desired, at least one filter unit (13,15) may be additionally impregnated with an alkali-metal humectant (such as potassium formate) and/or an organic amine compound selected from the group formed by urea and the alkanol amines (such as tris-hydroxymethylaminomethane). At least one filter unit may also be impregnated with a pH indicator substance. |