In the context of the modernization of the Chilean standard for domestic gas facilities, the development of an engineering tool for designers and builders of natural draft chimneys installed in social buildings is aimed at improving quality and security, preventing multiple poisoning cases by inhalation of CO given off frequently in older facilities. The present study shows a simple one-dimensional model, validated by experimental data obtained in a test chimney for a building of five floors. The software is developed in Visual BASIC and calculates the pressure and temperature distribution in different sections of the main chimney. On purpose, it incorporates the calculation of the draft in the secondary chimney that connects the gas combustion appliance to the main chimney, this information begin relevant in the tests applied by the Chilean certification entities, of these systems. Also, a test facility based on the British Standard BS 7 15 is constructed to analyse the wind effect over the cap located at the exit of the chimney. Then the variation of load loss due to wind effect is obtained from the performed tests. (C) 2007 Elsevier B.V. All rights reserved.