Porous burners are one of the technologies that are used to reduce fuel consumption and pollution formation in combustion applications. Less generation of NOx, preheating of the fuel-air mixture and higher delivery thermal power are among the favorable features of these kinds of burners. Moreover, all of the mechanisms of heat transfer are active in these types of burners, while other types of burners may not be able to take advantage of all heat transfer mechanisms. Other distinguished features of porous burners are the wide range of fuel-air ratio operating range, extended dynamic power range, compactness, uniformity of temperature distribution inside the combustion chamber, and higher warm-up efficiency. These distinct advantages of porous burners have made them a prime choice in applications such as residential heating systems, steam generation, dryers, and propulsion systems. The present work aims to assess different parameters on the combustion performance in porous media. A 5 kW porous burner has been designed and built to be used in the experiments. Natural gas is used as the fuel. Air and fuel flow rates are measured by means of rotameters. Thermocouples are installed along the burner to measure temperature profile. A data logger capable of recording 16 temperature measurements simultaneously, is used to collect data. About 50 data per second is recorded, which results in an enormous volume of data in the time span of experiment. Two types of tests are performed in this study. The first type concerns with the monitoring of flame and pollution emission from the porous burner during steady-state working conditions. In this regard, the effect of porosity (10 ppi, 20 ppi, and 30 ppi) is studied in the flame characteristics. It is found that a combination of 30 ppi medium as preheating zone and a 20 ppi medium as the combustion zone provides a plausible arrangement. The effect of fuel-air ratio is studied in a very wide range of this ratio. The present configuration enables a reduction of fuel-air ratio up to 0.3 for the aforementioned fuel. The main pollutants, CO and NOx, are measured in the above range. It was found that the amounts of these pollutants are much below the usual range in the free flames. Different regimes of flame, namely the under-surface, over-surface, detached, and buried, are observed during the tests. These regimes are closely related to the firing rates of the burner. The second type of tests concerns the transient behavior of flame in the porous burner. The concept of flash-back in porous burners is explained in this study, and a new concept, the flash-back temperature, is introduced. In this type of test, the effect of firing-rate and porosity are investigated. The porous burner is studied with one layer of 30ppi porous for the preheating medium and either a 10 ppi or a 20ppi medium for the combustion zone. It was found that by changing the firing-rate, all the regimes of porous burner may appear in the 30ppi-20ppi arrangement. Moreover, the combination of 30ppi-10ppi burner was proved useful as it does not permit a detached flame. k ew words : porous media burner, equivalence ratio, firing rate, pollution, flash back.