When in operation it is very loud and creates hissing noises at various pipework connections. The information plate on the compressor has become difficult to read, but there is an operating procedure kept in the office. The procedure states the operating limits of the unit, although the system itself has never been measured or checked by workers. These compressed air blow guns are connected to the compressed air outlets, via ten-metre flexible hoses trailing along the floor. There is no indication of which flexible hose leads to which outlet other than following the line to its termination point. Workers feel it is a waste of time checking the pressure gauges as there is plenty of force behind the air stream. What measures should be taken to prepare for safe maintenance of the compressor unit?