A method and kit for determining a concentration of iron in brake fluid when contacting a colorimetric reagent such that a color results. Specifically, a method and system is provided that allows a control panel of a secure access system to verify the authenticity and fidelity of a reader within the secure access system by utilizing a rolling code agreed upon by the reader and the control panel. The gangway and its associated cage are slidably connected to the platform via a track carried along the side of the platform. The detector is configured to detect whether the service information stored in the first memory is appropriate each time the communications terminal starts a call connection operation to use the specific communications service based on the condition information. The data controller has a priority-reset means for increasing a priority of a received data before being sent. The filling is accomplished by cooling a pressure vessel, filling said vessel with at least one type of gas at a temperature which is higher than the boiling point thereof and closing the cold vessel.