ISO 20645:2004 specifies a method for the determination of the effect of antibacterial treatments applied to woven, knitted and other flat textiles. ISO 20645:2004 is applicable to testing hygienic finishes of hydrophilic, air-permeable materials or antibacterial products incorporated in the fibre. A minimum diffusion of the antibacterial treatment into the test agar is necessary with this procedure. ISO 20645:2004 is applicable to other materials, provided that it is adapted accordingly. ISO 20645:2004 is not suitable for testing textiles treated with antibacterial treatments that react with the agar.