Aim: To investigate the antimicrobial effect of ionization on bacteria in household refrigerators. Methods and Results: Ionizer prototypes were tested with respect to their technical requirements and their ability to reduce surface and airborne contamination in household refrigerators. Ion and ozone production of the tested prototypes were measured online by an ion meter and an ozone analyser. The produced negative air ion (NAI) and ozone amounts were between 1 center dot 2 and 3 center dot 7 x 106 NAI cm-3 and 11 and 19 ppb O-3, respectively. To test the influence of ionization on surface contamination, different materials like plastic, glass and nutrient agar for simulation of food were inoculated with bacterial suspensions. The reduction rate was dependent on surface properties. The effect on airborne bacteria was tested by nebulization of Bacillus subtilis-suspension (containing spores) aerosols in refrigerators with and without an ionizer. A clear reduction in air contamination because of ionization was measured. The antimicrobial effect is dependent on several factors, such as surface construction and airflow patterns within the refrigerator. Conclusions: Ionization seems to be an effective method for reduction in surface and airborne bacteria. Significance and Impact of the Study: This study is an initiation for a new consumer tool to decontaminate domestic refrigerators.