SST Model GC801 Combustible Gas NOVA-Sensor for Inaccessible Locations is the solution when your sensor must be located on a high ceiling, under a raised floor, above a large piece of equipment, or in other hard to reach locations. The sensor electronics is mounted at eye-height where it can be easily viewed, while the gas detector only is located in the inaccessible location. Three conductors are required between the electronics and the detector. Lastly, connect a length of plastic or stainless steel tubing to the calibration gas fitting on the detector and route it to the electronics location. A technician can now test or calibrate the sensor, using the mode pushbutton on the electronics and applying test and calibrating gas to the detector through the tubing.