My gas furnace occionally makes a loud boom.?

My furnace occasionally makes a loud exposion when it ignites, contrary to the soft ignition that usually occurs when it comes on. The force of this blast knocks dust from the inside of the furnace and burning smells also result. Another thing that happens when it does this is that the flames burn mostly orange and yellow and are more widespread than usual along the coils. What is this, why is this, and will the furnace need to be replaced? And the furnace has been inspected recently.