Ozone smell is a sharp and fresh scent often perceived after storms, near electrical devices, or at high altitudes. Its etymological root is derived from the Greek word ozein, meaning “to smell.”
We can examine the nature and causes of this smell under the following headings:
Chemical Structure and Scent Character
Ozone (O3 ) is an unstable molecule composed of three oxygen atoms. Its smell is generally described as follows:
* Metallic and Pungent: It has a sharpness similar to bleach or chlorine.
* Fresh and Clean: It is the main source of that “clean” feeling in the air after rain.
* Burnt Electrical: It is the slightly burnt smell heard when electrical arcs occur.
Why Does Ozone Smell Occur?
For ozone to form, oxygen (O2 ) molecules in the air must be broken down by high energy. This energy comes from two main sources:
* Lightning and Thunderstorms: Massive electrical discharges during a storm break down nitrogen and oxygen molecules in the air. As these atoms recombine, some form ozone. This scent, carried by the wind just before rain begins, is a harbinger of the storm.
* Electrical Devices: Copy machines, laser printers, old televisions, or electric motors can produce small sparks (arcs) when operating. These sparks convert ambient oxygen into ozone.
Health Considerations
Although ozone is a vital shield in the stratosphere protecting us from UV rays, it is a toxic gas at the levels we breathe (ground-level ozone).
* Low Concentration: The human nose is very sensitive to ozone; it can immediately detect concentrations even at parts per billion (ppb) levels. At these levels, the smell merely gives a “freshness” sensation.
* High Concentration: If the ozone smell is very dominant in an indoor environment; it can cause throat irritation, coughing, chest pain, and headaches. Especially when using devices marketed as air purifiers like “ozone generators“, the environment must be very well ventilated.
Post-Rain Scent, Petrichor (Earth Smell)
The dominant earthy smell that reaches our noses when the rain subsides is scientifically called petrichor. This smell has no relation to ozone. Its sources are:
* Geosmin: It is a compound produced by certain bacteria living in the soil. When raindrops hit dry soil, this compound mixes with the air. The human nose is incredibly sensitive to this smell (it is said that we are even more sensitive than sharks detecting blood in water).
* Plant Oils: Special oils secreted by plants during dry periods and absorbed into the soil are released into the atmosphere with the rain.