Carbon-13C monoxide-18O (¹³C¹⁸O) is an isotopically labeled variant of carbon monoxide, composed of the carbon-13 isotope and the oxygen-18 isotope, giving it the molecular formula ¹³C¹⁸O. As a diatomic molecule, it retains the linear geometry and bonding characteristics of regular carbon monoxide (CO), but its isotopic composition alters its physical properties, such as molecular weight (approximately 31 g/mol) and vibrational spectra, making it useful in advanced spectroscopic studies, tracer experiments, and reaction mechanism investigations in chemistry and environmental science. This gas is colorless, toxic, and flammable, similar to regular CO, and must be handled with appropriate safety precautions.