A sensitive F2 absorption diagnostic technique was used to determine F2 densities in the flow of a 10.2‐cm‐long combustion‐driven chemical‐laser nozzle. The diagnostic device was demonstrated to be readily transportable and operable in a combustion‐driven chemical‐laser field environment. Cold‐ and hot‐flow measurements up to 970 K plenum temperature (i.e., no F2 dissociation cases) were in agreement; hence, the measurement technique appears to be reliable. The use of C2H4 as a combustor fuel did not result in particulate absorption or scattering of sufficient magnitude to affect the measurement. The flow dissociation level (α) was ≳0.8 for this nozzle. The measurement sensitivity achieved in these tests was ΔI/I0=6×10-4, which corresponds to an F2 density of 6.76×10-6 mole/l (i.e., 0.127 Torr F2 at 300 K) for a 10.2‐cm path length.