We present our direct tunable diode laser absorption spectroscopy (dTDLAS) approach targeting accurate HCl measurements in different matrices motivated by combustion emissions such as large-scale power stations or biomass burning domestic boilers. The system is based on a Mid-IR interband cascade laser (ICL) at 3.6 μm probing a HCl transition line in its fundamental band in a 38 cm single pass cell. The dTDLAS system is projected to directly derive absolute HCl concentrations in hot gas plumes with enriched H₂O vapor and CO₂. The system achieves a noise-equivalent (1σ) sensitivity of 1.0×10⁻⁵ cm⁻¹Hz^−1/2 for HCl. Integration over 60 s yields a sensitivity of 38 ppb at a meter path length.