A fire alarm algorithm based on the detections of smoke, and CO or CO2 concentrations will be sufficient for the heptane and toluene fires as shown in Fig. 5 and Fig. 6, since all three measured components rise at about the same time. However, for the fire test of HDPE in Fig. 7, a fire alarm algorithm must be based on the detections of smoke, CO and CO2 concentrations in order to detect this fire on time. Certainly, a fire alarm algorithm based solely on the detections of smoke and CO2 concentrations will detect the fire at a much later time after the visual onset of the fire, since CO2 concentration rise at a much later time compared to smoke concentration. Moreover, the smoke sensor alarmed 306 s after the visual onset of fire.