Wildfires occur in different climatic zones, forest cover types and eras. Wildfire or forest fire has always shaped the landscape. Different methodologies and indexes have emerged to determine the likelihood of wildfire, commonly confused with the wildfire hazard. However, none of these are universal or portable. In this paper, we have gone through several articles, projects and books. The aim was to identify factors related to the ignition of a wildfire. Consequently, 28 factors were presented and categorized into climatic, topographic, in-situ, historical and anthropogenic factors. It is the first step in building a generalized, acceptable and portable method to determine the wildfire risk. Its creation is strongly related to the prevention and better assessment of this phenomenon.

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Measurement of ambient NO 2 concentrations using diffusion tube samplers is widespread in many countries. Results from a program of measuring ground-level concentration of NO 2 at 20 urban sites within the city of Beirut are presented. In addition, two curbside sites were implemented at different heights. Two-week sampling period measurements were performed over 41 periods for all sites. A study of the sites' behaviors was conducted using principal component analysis and agglomerative hierarchical clustering. Firstly, results indicate that urban sites are equivalent, and one global class is identified. Any further monitoring of the nitrogen dioxide concentration can be conducted by decreasing the number of urban sites. Secondly, nitrogen dioxide concentration levels present a seasonal variation, as expected. Maximum average concentration of 178 μg m −3 was observed during

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