The present invention relates to a system for measuring respiratory function of living organisms. When the combustion mode is established to the compression ignition combustion mode, the apparatus establishes the valve timings of the exhaust and intake valves so as to form a negative overlap period in which both exhaust and intake valves concurrently close in the neighborhood of the exhaust top dead center. The box also has a diffusion element holder disposed proximate its front end, and even may have multiple diffusion element holders including having one diffusion element holder at an angle. Wherein at least one of the sidewalls has a bent portion bent from a front edge thereof, and the bent portion defines a hook at the tip thereof for adapting to retention at least one hole of the alignment wall of the insulative housing. The read controller is configured to receive a temperature sensing signal from the temperature sensing circuit, and inhibit a data read operation by the read circuit when the temperature sensed by the temperature sensing circuit is higher than a preset temperature.