Short answer
Cold nebulisation is a diffusion technique in which scent liquid is converted into very fine particles without heating and without adding water. These particles are then spread through a space by the air.
No water reservoir
With ultrasonic aroma diffusers, fragrance is usually added to water and spread as a visible or almost visible mist. A cold-nebulising professional system does not need that water.
As a result, no water reservoir needs to be refilled and the scent experience is created directly from the dedicated scent liquid.
No heat
Heat is not needed either. That is relevant because perfume compositions consist of volatile raw materials. Cold processing avoids the system having to heat the scent first in order to spread it.
Highly controlled dosing
Professional nebulisation is not about producing as many particles as possible. By setting work and rest intervals, a limited amount of scent liquid can be spread through the space in a controlled way.
That makes microdosing possible: just enough to create the desired scent background.
Is nebulisation the same as an aerosol?
No. An aerosol or manual spray usually produces a short, local cloud with a quick peak. A scent system is programmed to treat a space more evenly over a longer period.
Why does the space matter?
Even with the same nebulisation technique, the result can vary greatly. A small closed reception area calls for a different setting than a large shop with automatic doors.
That is why the output must always be fine-tuned in practice.
For which applications?
Cold nebulisation is used in retail, hospitality, offices, showrooms, fitness, wellness and other commercial environments where a consistent ambient scent is desired.