In this study the thermal ignition and explosion of carbon particle clouds, which are accidentally exposed to hot air contained within a confined geometry, have been theoretically examined. The effect of the nonuniform temperature distribution inside the particles on the ignition and explosion delay has been considered. The results were quantitatively compared with those acquired by assuming a uniform interior particle temperature. The effect of radiation is also investigated. Even if the temperature was approximately uniform inside the particle, any nonuniformity of particle temperature played a more significant role in reducing the explosion delay than in reducing the ignition delay as the particle size increases. This result was more obvious as the initial gas temperature decreased. Therefore, in order to predict the ignition and explosion delays of large particles for low initial gas temperature, it is essential to account for the nonuniformity of the interior particle temperature. It was also found that in contrast to the ignition delay, both the initial gas temperature and the particle loading ratio plays a significant role in determining the explosion delay.