Experimental measurements of the conditions required for the development of detonation in a 7 mm tube following ignition by a low energy spark are reported. There are then compared to previous experimental propagation limit criterion using theoretical predictions of detonation cell sizes based on a one-dimensional detonation length scale computed using a detailed chemical kinetic scheme. Technical difficulties precluded direct cell size measurements. Ethyl e ne-oxygen and hydrogen-methane-oxygen mixtures were investigated as well as methane-ammonia-oxygen, at initial pressures and temperatures in the ranges 1-7 bar and 293-540 K, respectively, The likelihood of detonation in ethylene-air mixtures in 150 mm and 50 min pipes at ambient initial conditions is also discussed in relation to published cell width data. The results indicate that whilst detonation cell width predictions do not provide a quantitative measure of the conditions for which detonation may develop in a pipe of given diameter, for prescribed initial conditions, predicted detonation cell size data does provide useful qualitative guidance as to possible hazardous compositions, particularly if preliminary experimental safety testing is thought to be necessary. (C) 2008 Elsevier B.V. All rights reserved.