Abstract: Chemical analyses of volcanic, geothermal and low enthalpy fluids are carried on to investigate volatile evolution. The methods used are mainly two: collection of residual gases and total gases. Both are valid, but for different use. In residual gases one can analyze ratio gas/steam, minus and major components but no carbon monoxide because interference with sodium idroxide. In total gas is difficult to analyze minus components but it`s good for carbon monoxide and isotopic composition in carbon dioxide. In both sampling methods the problem is to choose a good way for sampling. This manual shows the methods we consider the best in use. Another problems is to minimize analytical error. It depends from the quality of instrumentation and the quality of methods we use. We describe the methods in use in IGG laboratories that give good results, according with quality of instrumentation, quality of standard and reproducibility. We think that may exist other valid methods to collect and analyze samples. The methods we describe are just a starting point, it depends on the ability of researchers and operators to find methods valid for particular sites. In addition are described preparation of bottles for sampling different kinds of natural manifestations. There are different preparations in residual flasks if we sample volcanic fumaroles or geothermal wells. In addition to this some problems can comes from the pressure inside the bottles. We solve the problem with a particular apparatus self made for working at very low pressure, even under one hundred mbar.