The adsorption of N₂, O₂, fluoromethane (CH₃F), and chloromethane (CH₃Cl) gases was explored onto a BeO nanotube (BeONT) by density functional theory calculations. N₂, O₂, and CH₃F interact weakly with BeONT, so it cannot be employed as a sensor. Nevertheless, there is a considerable increase in the sensitivity and reactivity of the sheet through the CH₃Cl approach. There is a reduction in the HOMO–LUMO gap of BeONT from 7.03 to 4.30 eV (~ − 38.8%) when CH₃Cl is adsorbed, thereby increasing the electrical conductivity to a great extent. Hence, it is possible to convert the considerable change in conductivity into an electronic signal, which demonstrates the encouraging nature of BeONT as a sensor to detect CH₃Cl. Additionally, the adsorption process reduces work function of BeONT to a great extent, which demonstrates that we can also employ it as a work function-type sensor for detecting CH₃Cl among the mentioned molecules. The recovery time for the BeONT was calculated to be 18.6 s for CH₃Cl desorption, representing a short recovery time.