A storage system comprising: a storeroom; and an inside air control system that regulates a composition of inside air in the storeroom, the inside air control system including a pump unit, wherein a first gas outflow port of the pump unit is connected through a first gas supply tube to an air control valve and a second gas outflow port of the pump unit is connected to one end of a second gas supply tube, wherein the air control valve is connected to a gas release tube opening into the atmosphere and an air supply tube that communicates with an internal space of the storeroom; a filter box, concentration sensors that detect concentrations of components of the inside air, the concentration sensors including both of an oxygen sensor that detects an oxygen concentration of the inside air and a carbon dioxide sensor that detects a carbon dioxide concentration of the inside air; the concentration sensors being disposed outside the storeroom, the storage system having an air passage (48, 54) that communicates with the internal space of the storeroom and the concentration sensors, wherein: the inside air control system is configured to allow outside air to pass through the filter box and to be taken into the pump unit, the pump unit is configured to produce a supply gas having regulated oxygen concentration and carbon dioxide concentration through an adsorbent or separation membrane, the supply gas being supplied through the first gas supply tube and the air supply tube into the internal space of the storeroom, the second gas outflow port is configured to be closed to block the gas from the pump unit toward the second gas supply tube at a timing of detecting the oxygen concentration and the carbon dioxide concentration and to supply the inside air through an introduction tube to the concentration sensors and to return the inside air that has passed through the concentration sensor through a return passage into the internal space of the storeroom, and while the oxygen concentration and the carbon dioxide concentration of the inside air are detected, the pump unit is configured to be operated and a control unit is configured to continuously control the pump unit so that the inside air in the storage room has an intended composition a storeroom; and an inside air control system that regulates a composition of inside air in the storeroom, the inside air control system including a pump unit, wherein a first gas outflow port of the pump unit is connected through a first gas supply tube to an air control valve and a second gas outflow port of the pump unit is connected to one end of a second gas supply tube, wherein the air control valve is connected to a gas release tube opening into the atmosphere and an air supply tube that communicates with an internal space of the storeroom; a filter box, concentration sensors that detect concentrations of components of the inside air, the concentration sensors including both of an oxygen sensor that detects an oxygen concentration of the inside air and a carbon dioxide sensor that detects a carbon dioxide concentration of the inside air; the concentration sensors being disposed outside the storeroom, the storage system having an air passage (48, 54) that communicates with the internal space of the storeroom and the concentration sensors, wherein: the inside air control system is configured to allow outside air to pass through the filter box and to be taken into the pump unit, the pump unit is configured to produce a supply gas having regulated oxygen concentration and carbon dioxide concentration through an adsorbent or separation membrane, the supply gas being supplied through the first gas supply tube and the air supply tube into the internal space of the storeroom, the second gas outflow port is configured to be closed to block the gas from the pump unit toward the second gas supply tube at a timing of detecting the oxygen concentration and the carbon dioxide concentration and to supply the inside air through an introduction tube to the concentration sensors and to return the inside air that has passed through the concentration sensor through a return passage into the internal space of the storeroom, and while the oxygen concentration and the carbon dioxide concentration of the inside air are detected, the pump unit is configured to be operated and a control unit is configured to continuously control the pump unit so that the inside air in the storage room has an intended composition the inside air control system is configured to allow outside air to pass through the filter box and to be taken into the pump unit, the pump unit is configured to produce a supply gas having regulated oxygen concentration and carbon dioxide concentration through an adsorbent or separation membrane, the supply gas being supplied through the first gas supply tube and the air supply tube into the internal space of the storeroom, the second gas outflow port is configured to be closed to block the gas from the pump unit toward the second gas supply tube at a timing of detecting the oxygen concentration and the carbon dioxide concentration and to supply the inside air through an introduction tube to the concentration sensors and to return the inside air that has passed through the concentration sensor through a return passage into the internal space of the storeroom, and while the oxygen concentration and the carbon dioxide concentration of the inside air are detected, the pump unit is configured to be operated and a control unit is configured to continuously control the pump unit so that the inside air in the storage room has an intended composition