Accidental fire is a major concern in terms of safety of infrastructures and human lives. With the technological advancement, several novel methods are developed for minimizing the damages caused by the fire. One of the methods is to paint the base metals/ material with fire retardant coatings which can increase the lead time so that economic destruction and loss of human lives can be avoided. In this work, the performance of the intumescent coating (passive type fire retardant coatings) is studied with the help of cone calorimeter and open pool diesel fire as sources of heat. The transient temperature distribution for bare Stainless Steel 310 plate suggests that the cone calorimeter experiments alone cannot suffice for mimicking real life conditions. Comparison of the behavior of the available paints in cone calorimeter and open pool fire confirms that the performance of intumescent coatings in cone calorimeter is very different from that in open pool fire. The safe initial thickness of the intumescent coating is a function of heat release rate of the source. The effective thermal conductivity of the intumescent coatings is evaluated using one dimensional conduction heat equation with constant boundary temperature condition.