Recently the hot air gun I use for desoldering components stopped heating beyond a point. It was heating but nowhere close enough to melt the solder. A bit of troubleshooting lead me to believe that the ceramic coil heater on the tip of the heat gun was the problem. Opened it up and replaced it with a new unit and the heating is back to normal. Seems heating element damage is quite common in the hot air guns as there are quite a few sellers selling spare parts for this very issue.
The ceramic heater works on the principle of resistive heating. It contains a coiled metal wire(I am guessing it’s Tungsten? due to its high melting point). The Coiled metal wire has a finite resistance. I measured the DC resistance on the new one to be around 330Ohms. When a large current passes through it, it heats up to red hot and transfers heat to the ceramic material too. The heater knob in your hot air station increases the current to the element when you turn up the heat. There is an air pump(I did a teardown of this last year) which takes air and pumps it through the heater to heat up the output air which you use to desolder parts.
One pro tip to prevent the heater tip from going bad fast(For cheaper workstations) is to always increase the airflow and the heater knob simultaneously. Having low air flow and a heater in a very high setting is bad for the coil heater.