In this work we used the multi-energy method to estimate the overpressure and the positive phase duration as a function of the distance from the explosion center, resulting from vapor cloud explosions of LPG-air mixtures in highly congested areas near an LPG storage park. Simulations were made for square shaped zones planted with 10 m high trees and areas ranging from 50,000 to 250,000 m(2). The criterion used to evaluate the risk to a LPG storage sphere was the stress failure of the diagonal arm braces supporting it. The explosion effects were studied for a 14.5 m diameter LPG storage sphere, located at distances ranging from 10 to 100 m away from the border of the congested area. It is shown that congested areas of at least 100,000 m(2) can pose a risk to the LPG spheres with minimal filling. It is possible to conclude that it is better to keep a smaller number of full filled spheres than many spheres with less filling of LPG. We estimated for congested areas with 25% blockage ratio that the minimum safe distance, measured from the border of the tree grove to the sphere, varies from 10 m, for 100,000 m(2) areas, to 87.6 m, for 250,000 m(2) areas. The tree spacing influence represented by the blockage ratio was also analyzed, showing that it affects the sphere minimum safe distance. Finally, recommendations are made regarding the minimum safe distance between the spheres and the congested area, which seems to have a maximum value, as well as other ways to lessen the risk represented by explosions, but further conclusions would require a different approach as the loading would be dynamic instead of impulsive for tree belts with areas bigger than 250,000 m(2). (C) 2004 Elsevier Ltd. All rights reserved.