Abstract: Apparatus for removably connecting a calibrating gas chamber to the body of an electrochemical sensor consisting of corresponding members carried by the sensor and the gas chamber, each member defining a contact surface that cooperates with the contact surface of the corresponding member to removably secure the surface together so that connection of the chamber is accomplished by contacting the surfaces of the corresponding members and the chamber can be removed when calibration of the sensor is finished for connection to another sensor or reconnection to the same sensor at a later time. In a preferred embodiment the corresponding members are composed of Velcro fabric.