This study deals with the ability of Rice Husk Biochar (RHB) to adsorb and reduce the concentration of 90 ppm Nitric Oxide (NO) gas which passed through it with a 1.2 liter/min flow rate within 8 minutes. The characteristics of biochar before and after adsorption were studied by SEM, EDAX, and FTIR analyses. To study the effect of different factors on adsorption the effect of manufacturing temperatures of biochar was studied by using two degrees 450 °C and 500 °C. It has also been measured the effect of biochar particles size using two types of size, coarse (C) and fine (F). The effect of the shape of the measurement system on the adsorption was also measured using two types of systems A and B. In general, the RHB450C A gives the best adsorption capacity for NO (95.7 mg/g) followed by RHB450F A (41.9 mg/g) followed by RHB500C A (24.8 mg/g). Both Langmuir and Freundlich isothermal models were applied to mathematical modelling of NO adsorption, and based on the coefficient of determination (r2) Langmuir’s model provided a perfect fit to the experimental data. It was also found that the pseudo-first-order model is suitable for studying adsorption kinetics.