Installation of air filters; Cleaning of filters for air purifiers; Maintenance of air filters; Repair of air filters; All the aforesaid filters being particle filters and sorption filters, namely, for adsorption and chemisorption; All the aforesaid filters being sorbent-impregnated open-pored foams and sorbent-covered textiles being woven, non-woven and molten supports, in particular spherical activated carbon, granular activated carbon, ion exchangers, super-absorbers and impregnated sorbents