Can the hair dryer cause a fire when the plug is unplugged but the switch is turned off? What is the principle?

The cause of the fire was that the switch was turned off, but the heating element was not turned off.

Schematic diagram of two-speed blower

The schematic diagrams of the above two gear blowers are as above. For one-button hair dryer, you can see that when OB is connected, only the motor works and blows cold air.

When OB and OA are connected, hot air can be blown out. After this shutdown, the heating wire must be cut off, unless the internal circuit is too old, it will not cause a fire.

Hair dryer with 2 switches

For a hair dryer with two switches, one switch controls the fan and the other switch controls the heating wire. If interlock and protection are not involved in the circuit, if only the fan switch is turned off, the heating wire will still be electrified and heated, so it will cause a fire. General regular manufacturers will do chain, because this is not difficult to do, and the industry must also have requirements.

However, it is not excluded that individual manufacturers shoddy.