According to the World Health Organization, contact with atmospheric airborne pollutants (CO, CO2) causes 4.2 million deaths annually. Globally, there is a well-established demand for highly sensitive, inexpensive, and energy-efficient miniaturized gas sensors that can be used to identify and steer clear of high pollution hotspots. According to first-principles calculations, the current study presents the first report of a single-layer MoSe2 monolayer nanoribbon as a potential sensor for carbon-containing gases (CCGs) that are ecologically harmful. On MoSe2, calculations and discussions are made on the adsorption energies and configurations that are most stable. In order to track the modifications in the electronic characteristics subsequent to gas molecules adhering to the MoSe2 single layer, the density of states (DOS) and energy band structures (Eg) were also examined. The recovery time is also calculated for all the carbon-containing gases (CCGs) used here. The maximum adsorption energy for CO2 is around −0.76 eV, while Ead, i.e., the adsorption energy of CO is approximately −0.55 eV. The outcomes of band structure and DOS indicate that there may be a stronger connection between CO2 and MoSe2 monolayer than there is with CO gas. Additionally, the recovery time plot demonstrates that the MoSe2 monolayer sensor gets the required time to detect CO2 gas.