Model fire experiments were carried out to characterize the properties of fire plume given by a diffusion flame in an enclosure with downward air flow. Using methylalcohol as a fuel, a pool fire source providing three different fire size of φ100, 150 or 200mm was used with a downward velocities of .25 and 45 cm/sec. The decreasing mode for both excess temperature and velocity along the vertical flow axis revealed the same modes observed in the free boundary condition. The horizontal plume radius estimated from the temperature showed much wider than that from up-ward velocity distribution in an enclosure with a downward flow. The horizontal distribution of excess temperature was approximated by Gaussian distribution.
