Abstract: This invention consists of breath testing apparatus 10 comprising a breath tube 11, a fuel cell housing 12 incorporating a pump system 12a, a fuel cell 13, a control and computational unit 14, and a display 15. A thermistor 22 is provided to detect the temperature of the housing 12 during measurement and the unit 14 compensates the fuel cell output in accordance with the detected temperature.

Abstract: A fuel cell sensor (10) comprises a main body (11) in which are mounted working electrodes (12), counter electrodes (13) and respective contacts (14 to 17). The working electrodes (12) are mounted facing each other to define a sample space between them. The electrodes (12) are electrically interconnected in parallel as are the two counter electrodes (13). This arrangement makes it possible to provide a very large working electrode surface area for a small volume sample space (22).

Abstract: Testing apparatus is provided in the form of a pen and has a body 11 and cap 12. The body 11 has an inlet 13 at its tip which communicates with a fuel cell chamber 14, containing a fuel cell 15, and, via that chamber, with a passage 16 and a cylinder 17. A piston 18 is mounted in the cylinder 17 for operation by a button 19, a spring 21 and latch 22 such that it can draw air through the inlet 13 to the fuel cell 15. If the inlet 13 is placed in a user's mouth the apparatus can provide an indication of his breath alcohol concentration, for example, on display 23.