Hydrogen is the most ideal and promising alternative fuel, and fuel cell vehicles that use hydrogen as a fuel are expected to be widely used in public. To use hydrogen commonly, the establishment of proper guidelines for handling safely is required urgently. In a series of research to develop safety data of hydrogen systems, the accurate evaluations of the effect of blast wave from hydrogen explosion were examined. In the case of deflagration, measured blast pressure is influenced largely by thermal strain of the diaphragm of the pressure sensor due to the radiation from the flame. In present work, reduction of the effect of radiation to pressure sensor with recess mount was estimated by calculation using view factor. The natural frequency and the response of the recess mount sensor were also evaluated. The validity of recess mounted sensor was shown through the experiments on the blast waves measurements of hydrogen/air denigration. Blast waves were measured by using both pressure sensors with recess mount and with conventional flush mount. The recess mount method suppressed the effect of radiation remarkably without lacking the accuracy.