Because door handles are commonplace and are interacted with by large numbers of people on a daily basis, they present opportunities for growth of bacterial colonies.
Many factors determine the habitability of a door handle for a population of bacteria. The material of the handle itself contributes to the growth of bacteria, with most door handles being constructed of stainless steel – a suitable home for bacteria. The material can affect the time bacteria can survive on door handles, but more important is the temperature and humidity of the environment. A hospitable environment can allow bacteria to thrive for anywhere from a few hours to a few weeks on a surface.