A printer, such as an ink jet printer, incorporates various hardware such as the ink supply tank, tubing, and ink drop gutter, as representative items, having components molded in the hardware which disinfect groups of micro-organisms which present problems, particularly in areas where ink has depleted. The techniques described lead to inactivation of vegetative bacteria and fungi and prevention of maturation of spores in those areas not in frequent control with the biocide component of the ink. Also mutant forms are prevented from developing in those areas where the biocide component concentration is below the effective lethal level.