Scalp Protect Mode: What a Time-of-Flight Sensor Is Actually Measuring
Hair dryer features tend to be sold as more: more heat, more speed, more settings. Scalp protect mode is unusual because it is sold as less — less heat, applied automatically, exactly when you would otherwise not think about it.
It is worth understanding what is actually happening, because the mechanism explains both what the feature does and what it does not do.
The problem it is solving
A blow-dry is not one temperature. The air leaving the nozzle might be at a comfortable 140°F, but the distance between nozzle and scalp changes constantly while you work — close at the roots, further away down the length, closer again when you switch sides. The temperature arriving at your skin is therefore changing all the time, even though the setting on the dryer is not.
Most people compensate by holding the dryer further away than they need to, which slows drying, or by turning the heat down and accepting a longer session. Neither is a great answer.
What time-of-flight sensing does
A time-of-flight sensor emits a short pulse of light and measures how long it takes to bounce back. Since light travels at a known speed, that round-trip time gives a distance measurement — the same principle as the parking sensor on a car, at a much smaller scale.
In the Nural HD16, that reading is used to work out how far the dryer is from your head, and the heat is reduced as the dryer gets closer. Nothing is being measured on your scalp; the dryer is measuring its own position in space and adjusting accordingly. That is why it works without contact and without you changing anything.
In the manufacturer’s testing, using Scalp protect mode produced a 3x stronger scalp barrier and up to 96% more shine compared with air drying.
Two behaviours that surprise new owners
It overrides your heat setting. Activating Scalp protect mode replaces whatever heat level you had selected. That is the feature working as intended — a mode that protects the scalp cannot also honour a manual “maximum heat” instruction. When you switch it off, you are back to your own settings.
It does not switch off the moment you stop moving. Pause detect uses an accelerometer to notice when the dryer has been set down, then cuts the heater and drops the airflow. It is deliberately built with a 240 ms delay so that a momentary pause mid-section — the half-second where you reposition a brush — does not shut the heat off. Without that delay the feature would be unusable; with it, the dryer behaves normally while you style and goes quiet when you put it down.
Where it fits against the rest of the range
Scalp protect is not a replacement for good technique. You still move the dryer, you still keep it at a sensible distance, and you still finish with a cold shot to set the style — the HD16 offers four heat levels (212°F, 176°F, 140°F, 82°F) and three precise speeds for that.
What it changes is the failure mode. The bad blow-dry is usually not the one where you chose the wrong setting; it is the one where you stopped paying attention for two minutes near the roots. A sensor does not stop paying attention.
If scalp comfort is the reason you are shopping, the HD16 is the model in the range built around it. If weight and manoeuvrability matter more, the Supersonic r HD17 is 30% smaller and 20% lighter and does not carry the scalp sensor. If you simply want the proven original at the lowest price, that is still the HD07.
Also worth knowing
The HD16’s filter cage is magnetic and removable — wash it in warm soapy water, soak for at least 30 minutes, rinse and dry. A clogged filter is the most common cause of a dryer that feels weaker than it used to, and it is a five-minute fix rather than a service visit.
All models on this site ship with a 12-month warranty from the day they arrive.
