We report on the application of a compact and field-deployable instrument, based on a continuous-wave fiber-coupled Telecom external cavity diode laser, to measure the 13 C/ 12 C isotope ratio in CO 2 from a wood-based combustion. Carbon dioxide, the most important greenhouse gas, is a major product of combustion. The measurements of the 13 C/ 12 C isotopic ratio in CO 2 from combustion emission permit one to identify the CO 2 source and to study the temporal and spatial variations of pollution in the atmosphere. The average value of the 13 CO 2 / 12 CO 2 ratio is found to be (1.1011±0.0024)%. The corresponding δ-value relative to PDB standard is (−20.17±2.14)‰, which is in good agreement with the typical value of (−25±2)‰ for wood. Simultaneous monitoring of multiple species from gas emission has been performed using direct-absorption spectroscopy. The concentrations of C 2 H 2 , CO, CO 2 and H 2 O were determined on the basis of integrated absorbance measured by least-squares fitting a Voigt lineshape to experimental absorption spectra.