Laser Induced Breakdown Spectroscopy (LIBS) is a laser based analytical technique capable of providing quantitative evaluation of the chemical composition of gas, liquid and solid samples. The principle of operation relies on the generation of a breakdown plasma by means of high irradiance (> 1010 W/cm2) laser pulses. Light contributions emitted by the plasma are collected and spectrally analysed by a properly designed detection unit. Since chemical bonds are broken down in the plasma plume and ionization of constituent elements occurs because of the very high temperatures, it comes out that the observed light emission has been generated by the relaxation of the constituent excited species. As a consequence, the spectral content of the collected light can conveniently be used to determine the elemental composition of the sample. Since different experimental configurations have so far been used and different measurement parameters have been adopted (like e.g. pulse duration, energy per pulse, integration time, etc.), to evaluate the dependence of the resulting spectrum on the plasma characteristics we have developed a simulation program that allows generating the resulting spectra once plasma physical parameters (like temperature and electron density) are known. In particular we have used this program to evaluate the dependence of the measured elemental concentration on the time over which the emitted spectrum is detected (the so called integration time).