Avionics technicians are employed in several different settings. Most passengers inside a terminal have seen a line tech rushing to replace a black box so that a flight can leave on time, but the bulk of the work around a terminal is done at night. Pilots write-up problems in the aircraft log book during the day. Technicians try to clear those entries at night. They may be updating aircraft software, repairing wiring, or changing black boxes as necessary. The night crew technicians repair those time consuming items that could be deferred overnight, provided that safety is not compromised.
Hangar avionics technicians have the luxury of time, unlike the line techs. Their airplane may be in the hangar for days or weeks. A planner reviews the aircraft records and any new information from the manufacturer, and then works out a schedule to cover all the necessary routine and non-routine maintenance. Teams are assigned and the time required for each task is included on the schedule. Unanticipated problems, like a crushed antenna cable, can introduce delays, but the teams usually manage to get the work finished before the deadline.
Bench technicians work in well-lit, air-conditioned rooms surrounded by the hum of cooling fans. Avionics equipment manufacturers specify the temperature and humidity limits for testing. While not quite "clean rooms," most have dust collection systems and positive air pressure. Floors, benches, and office furniture are specially made to dissipate static electricity. Screen rooms that block electromagnetic interference are used to test extremely sensitive equipment, or to shield the surrounding areas from powerful radio transmitters.