The investigation of flame propagation accompanying the explosions of unconfined gaseous reactive clouds which are diluted in atmosphere ambient is a fundamental interest in the analysis of industrial risk assessment. Following the previous work [Sochet, L, Guelon, F., Gillard, P. (2002). Deflagrations of non-uniform mixtures: A first experimental approach, Journal of physics, 12, 7-273, 7-280], an experimental study is conducted on a deflagration of a hydrogen/oxygen gaseous cloud which is released in air. The burning velocity is directly or indirectly measured. The flammability limits of the non homogeneous cloud has been as well investigated. (c) 2005 Elsevier Ltd. All rights reserved.