Filling a kerosene heater 1- Do not fill it while it is hot for safety reasons. 2- Do not fill kerosene from one heater to another, as you will transfer impurities and rust as well. 3- It is best not to fill the heater directly. It is preferable to fill it using a funnel with a filter, such as a Coleman funnel. Because the filter in the Coleman funnel has very small pores. The dimensions of the pores in the Coleman Funnel filter are usually: - 100 microns (0.1 mm) This is the common pore size in fuel filters, and it is suitable for removing impurities and foreign particles from the fuel. 50-200 microns (0.05-0.2 mm) Some filters may have pores of different dimensions, but 100 microns is the common size. The percentage of rust reduction when using a funnel with a filter can reach 50-80% compared to direct filling. - Removing impurities and foreign particles from kerosene - Reducing moisture in kerosene - Improving fuel flow, i.e., regularly and not acceleratingly