Concern associated to smoke from forest fires has been increasing during the last past years. The severe air pollution episodes caused by fires in Amazonia, Indonesia and Philippines in 1997/98 and, more recently, in Australia, drawn worldwide attention to the problem. Currently, there is a growing awareness that smoke from forest fires can expose individuals and populations to hazardous air pollutants and the World Health Organisation even developed policies and guidelines to reduce the health impacts of smoke generated during vegetation burning. However, air quality data acquired during forest fires and accompanied with other important information, like meteorology, visibility, fire and combustible characteristics, is still reduced and it is not possible to completely evaluate the effects of forest fires on the air quality. The main purpose of this work is to contribute to a better understanding of forest fires as a source of pollutants to the atmosphere.

The burning experiments performed in Central Portugal, Gestosa, since 1998 till 2003 allowed measuring air pollutants concentrations during experimental fires. These experiments involving several teams and covering a very extensive characterisation of variables related to the fire behaviour constituted a great opportunity to analyse and measure air quality. From the first field campaign till the last one it is possible to notice a clear evolution of measurement approaches and techniques aiming to optimise the procedures.

The knowledge acquired during the previous burning experiments was fundamental to the organisation of Gestosa 2002 experiments and, during the main burns on the 30th and 31st of May, measurements of atmospheric emissions and air quality concentrations have been taken. Two luggage-vans were equipped with meteorological station and air quality analysers in continuum to get concentrations of PM2.5, PM10, NOX, and CO in the proximity of the burning plots. Taking into account the potentialities of the passive samplers technique, namely a larger spatial cover, sample locations around the burning plots were chosen and SO2 and NO2 were measured. Some of them were changed various times a day aiming to evaluate the influence of the burned plots characteristics in the air pollutants concentration values. Firemen and members of the research team carried a passive sampler during the two days of the experiments in order to estimate the human exposure to NO2 and SO2. Measurements of VOC emissions were carried out by sampling the smoke pumping it into TEDLAR bags and analysing it afterwards. Meteorological parameters, like temperature, humidity, wind speed and wind direction data were acquired.

This paper will present the concentration values measured during the Gestosa2002 experimental fires and will analyse the acquired values in an integrated way, taking into account not only the concentration values but also the involved variables, like the fire type and the combustion efficiency, and the meteorology, and identifying the possible correlation between them in order to contribute to a better understanding of the air pollution phenomenon associated to forest fires. The particular location of this study, South Europe, will be stressed because the available information concerning forest fires effects on the air quality (from emissions till ambient concentrations) mainly comes from other parts of the world.