A respiratory system , including: a gas supply unit including a gas supply port ; and a heating and humidifying unit being detachably combined with the gas supply unit , the heating and humidifying unit being electrically connected to the gas supply unit when combined with the gas supply unit , wherein the heating and humidifying unit includes: a base including a control element ; an adapter combined with the base and able to rotate at least 90 degrees relative to the base , wherein the adapter is electrically connected to the control element ; and a water tank being detachably combined with the base , the water tank including a gas inlet and a gas outlet , wherein when the water tank is combined with the base , the gas inlet penetrates through an aperture of the base to be fluidly connected to the gas supply port , and the gas outlet is fluidly connected to the adapter ; characterized in that the base further includes a fixing portion for combining with the adapter , the fixing portion includes a through hole and an inner wall , and the inner wall protrudes from a surface of the base and surrounds the through hole ; and wherein the fixing portion further includes a groove and at least one drain hole , the groove surrounds the through hole and the inner wall is located between the groove and the through hole , and the at least one drain hole is located at a bottom of the groove . a gas supply unit including a gas supply port ; and a heating and humidifying unit being detachably combined with the gas supply unit , the heating and humidifying unit being electrically connected to the gas supply unit when combined with the gas supply unit , wherein the heating and humidifying unit includes: a base including a control element ; an adapter combined with the base and able to rotate at least 90 degrees relative to the base , wherein the adapter is electrically connected to the control element ; and a water tank being detachably combined with the base , the water tank including a gas inlet and a gas outlet , wherein when the water tank is combined with the base , the gas inlet penetrates through an aperture of the base to be fluidly connected to the gas supply port , and the gas outlet is fluidly connected to the adapter ; characterized in that the base further includes a fixing portion for combining with the adapter , the fixing portion includes a through hole and an inner wall , and the inner wall protrudes from a surface of the base and surrounds the through hole ; and wherein the fixing portion further includes a groove and at least one drain hole , the groove surrounds the through hole and the inner wall is located between the groove and the through hole , and the at least one drain hole is located at a bottom of the groove . a base including a control element ; an adapter combined with the base and able to rotate at least 90 degrees relative to the base , wherein the adapter is electrically connected to the control element ; and a water tank being detachably combined with the base , the water tank including a gas inlet and a gas outlet , wherein when the water tank is combined with the base , the gas inlet penetrates through an aperture of the base to be fluidly connected to the gas supply port , and the gas outlet is fluidly connected to the adapter ; characterized in that the base further includes a fixing portion for combining with the adapter , the fixing portion includes a through hole and an inner wall , and the inner wall protrudes from a surface of the base and surrounds the through hole ; and wherein the fixing portion further includes a groove and at least one drain hole , the groove surrounds the through hole and the inner wall is located between the groove and the through hole , and the at least one drain hole is located at a bottom of the groove . <EOS>