Selecting the most appropriate flow measurement techniques with related devices to characterize potentially hazardous chemicals which emit flammable or toxic gases due to their hydro-reactivity poses a difficult but required task for official classification of such materials. This paper offers a careful examination of three such potential methods that differ from each other by the flow rate measurement device which includes one manual and two automatic systems. Experiments for comparative testing and validation limits have been defined and carried out for two known hydro-reactive chemicals: aluminum chloride and sodium borohydride. The main conclusions are reported here. From the results obtained, the possible selection of the best investigated methods is suggested according to performance based criteria. (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.