Add dirty hands, dust buildup, vandals, salt spray, electromagnetic interference and even explosions to the rain, sleet, snow and the gloom of night that can affect operation of access control systems, and especially readers in harsh conditions. And there is the stress on readers that must handle intensive traffic or electrical situations that can knock out gear for a period of time.
There have always been ruggedized readers such as vandal- and weather-resistant units that can perform in extremes. Some companies, often with petrochemical, healthcare and government clients, repackage units to tamp down any chance on causing trouble or spreading germs.