Sometimes very large fires burn up forests in the western United States. If you look at the picture you will see why it is so hard for fire fighters to put out these massive blazes. The smoke is so dense that it is difficult to locate the actual places where the fire is most intense from aircraft so that fire fighters and equipment can be sent there.
When the fire is viewed by the infrared radiation it sends out, it is possible to "see" through the smoke to the fire underneath.
Click on the other two images below. These were each taken in infrared light. One in light just beyond red (mid_IR) and the other even farther beyond red (Thermal IR). In the last picture, the smoke is almost totally invisible and the fires can be clearly seen.
These kind of techniques make the fire fighters job safer and easier.