How do hair dryers work?

The basic parts

Why warm, moving air dries hair

Water evaporates faster when it is warmer and when the air around it is constantly replaced with drier air. A hair dryer does both. The heater raises the temperature of the air and of the water on the hair, and the fan keeps sweeping away the moist air near the hair so evaporation continues.

That is why airflow matters as much as heat. Very hot air with little movement dries slowly and risks overheating hair. Strong airflow at moderate heat often dries faster and more gently. Our wattage explainer explains how watts relate to heat, and our guide to drying hair faster puts this into practice.

Motor, fan and heater

In a traditional dryer, a motor in the head spins a fan, and a coiled heating element, usually wire wound on a heat-resistant frame, sits in front of it. Electricity passing through the wire heats it, and the air flowing over it warms up. Heat settings switch parts of the element on or off, or vary the power supplied; speed settings change the motor speed.

High-speed dryers, like the Dyson Supersonic, Laifen and Dreame models, use small brushless digital motors that spin very fast; Dyson's Origin listing gives up to 110,000 rpm. They move a lot of air from a small, light motor, which allows lighter dryers and sometimes puts the motor in the handle for better balance.

Safety features

Every mains hair dryer has protection against overheating. A thermostat or temperature sensor keeps the air within limits, and a thermal cut-out switches the heater or the whole dryer off if it gets too hot, for example if the intake is blocked. Premium dryers measure temperature many times a second; Dyson's Origin listing describes a glass bead thermistor reading 40 times a second.

Most hair dryers are double insulated, which is why they have only two wires and no earth. Our explainer on why hair dryers have no earth wire covers this. UK plugs also contain a fuse that protects the cable. If your dryer keeps cutting out, see why a hair dryer stops working.

Note:Never block the air intake or outlet, never use a dryer near water and never open the casing of a mains appliance.

Ionic, ceramic and other technologies

Ionic dryers include a component that releases negative ions into the airflow. Brands say this reduces static and frizz. Ceramic and tourmaline coatings on internal parts are marketed as giving more even heat. Our explainers on ionic hair dryers and ionic vs ceramic dryers cover what these labels mean.

Some premium dryers add sensors. The Dyson Supersonic Nural, for example, adjusts heat as it moves closer to the scalp. Shark's SpeedStyle uses attachments that tell the dryer which head is fitted so it can adjust heat and airflow.

Nozzles and attachments

A concentrator narrows the airflow into a fast, flat jet for smoothing with a brush. A diffuser spreads the airflow out and slows it, so curls dry without being blown apart. Smoothing and flyaway attachments use airflow over a shaped surface to flatten stray hairs.

Our attachments explainer goes through each type. When you choose a dryer, the attachments in the box matter as much as the motor; see our guides to the best hair dryers in the UK, dryers for curly hair and lightweight dryers.

Frequently asked questions

Does a hair dryer use a lot of electricity? It draws a lot of power while running, but only for short periods. A 2,000 W dryer used for 10 minutes uses about 0.33 kWh. Our running-cost calculator works out the yearly figure.

Why does a hair dryer have a cool shot? It switches the heater off while the fan keeps running. Cool air sets the shape of hair as it cools, so styles last longer.

Why does my hair dryer cut out? Usually the thermal cut-out has tripped because the filter is blocked or the intake is covered. Clean the filter and let it cool.

What is a brushless motor? A motor that switches its coils electronically rather than with carbon brushes. It can spin very fast, run efficiently and last a long time.