The GCT External Pump is an accessory device to be used with Gas Clip portable gas detectors, powered by a rechargeable battery. The GCT External Pump is worn on the user's body and does not require regular interaction to perform its function. The device draws sample air from an inlet and delivers it through an outlet and a hose to a compatible calibration cap mounted on a GCT gas detector. During operation, a hose that is up to 75 ft (23 m) long with 1/8 in ID can be connected to the inlet to allow environmental sampling in confined spaces before entry into the space. For hose lengths up to 50 ft (15 m) GCT offers tubing that will not oxidize, is able to bend around sharp curves and easily works with GCT External Pump accessory fittings. For tube lengths over 50 ft (15 m), GCT recommends using tubing with even higher resistance to reactive chemicals (e.g. H2S). Please contact GCT for tubing selection recommendations. The GCT External Pump should be used only when remote sampling. Once the area in question has been cleared for entry, disconnect the GCT External Pump and calibration cap from the gas detector in order to resume normal detector operation.