A part of the comparison of methods for vent dimensioning of gas explosions by Razus and Krause (2001) has been revised. The semi-empirical methods by Bradley and Mitcheson (1978a, 1978b) and Molkov, Dobashi, Suzuki, and Hirano (1999) were equally accurate for tests with covered vent. Empirical correlations for duct vented gas and dust explosions were combined with the Molkov method to predict explosion overpressures measured in tests of duct vented gas explosions. Since 29 of the 65 tests were made with town gas-air mixtures, the values of burning velocity and expansion factor of such mixtures have been estimated. The correlations by Bartknecht (1993) and Siwek (1998) had comparable accuracies. The methods for duct vented dust explosions by Tamanini and Fischer (2003) and Ural (2005) were less accurate. Two new engineering correlations by Di Benedetto, Russo, and Salzano (2007, 2008) were found flawed. The parameters of the earlier correlation were fitted to test data. The later correlation was complemented with a term containing vent opening pressure. The revised correlations provided predictions comparable to those made with the methods by Bartknecht (1993) and Siwek (1998). (C) 2011 Elsevier Ltd. All rights reserved.