This communication explores the influence of boundary effects, embedded sensors and crack opening on high-temperature experiments of concrete as revealed by in situ neutron tomography. The hypotheses routinely taken about these experimental aspects in common practice are hereby reassessed in light of the insight given by noninvasive full-field measurements. Notably, we directly assess the heat and moisture insulation techniques and reveal the influence of temperature and gas pressure monitoring on the testing conditions, opening new perspectives toward their improvement.