Ozone (O₃)

Description:

Ozone (O₃) is a colorless to slightly bluish gas with a pungent, penetrating odor similar to that of chlorine. The olfactory threshold for human perception of this gas is 40 µg/m³.

It is one of the most important trace gases in the atmosphere and, at an altitude of 20 to 30 kilometers, forms the natural ozone layer, which protects us from the sun's harmful ultraviolet radiation.

Ozone is an unstable molecule that quickly breaks down into diatomic oxygen. In addition, O₃ is highly reactive (an oxidizing agent) and toxic to humans. It promotes combustion and can form flammable and explosive mixtures. Ozone is heavier than air.

Ozone limit values:

Because ozone breaks down rapidly under normal conditions, its concentration in the air should be close to zero and therefore not measurable.

The EU has established various one-hour thresholds for O₃, which describe the concentration at which effects develop within one hour. An information threshold of 90 ppb (parts per billion), equivalent to 180 µg/m³, was set. If this threshold is exceeded, the public must be notified. In addition, an alert threshold of 120 ppb (240 µg/m³) was established; reaching this level must trigger an ozone warning.

According to the Federal Environment Agency, the maximum 8-hour daily limit of 120 µg/m³ (60 ppb) may be exceeded on no more than 25 days per calendar year. In the long term, however, this limit should not be exceeded at all.

The former limit value (MAK value) of 100 ppb (200 µg/m³) has been replaced by the occupational exposure limit (AGW). Since an AGW for ozone has not yet been established, the former MAK value serves as a non-binding guideline. International occupational exposure limits are as low as 60 ppb (120 µg/m³).

Consequences of a concentration that is too high:

Ozone is absorbed through the respiratory tract and the eyes. Due to its strong oxidizing properties, exposure to O₃ can cause irritation and even long-term damage to the eyes and mucous membranes. Symptoms include hoarseness, coughing, headache, and nausea, as well as nosebleeds and bronchitis.

Since ozone affects lung function, it can, at high concentrations, cause pulmonary edema (accumulation of fluid in the lungs). People with pre-existing conditions or sensitivities—such as asthma or chronic bronchitis—are particularly vulnerable to the harmful effects of ozone. Furthermore, there is strong evidence to suggest that O₃ is carcinogenic to humans.

Performance is also affected by high levels of O₃ in the air, as this can cause fatigue and difficulty concentrating.

Source:

During electrical discharges in a thunderstorm, ozone is formed, among other substances. It is also formed through the process of photodissociation, in which, under high-energy solar radiation, oxygen molecules in the stratosphere split into two individual atoms—radicals that then react with an O₂ molecule to form O₃.

Ground-level ozone formation is the result of a complex reaction between oxygen, nitrogen oxides (NOx), and volatile organic compounds (VOCs) under intense solar radiation.

The precursor pollutants for this reaction come mainly from human sources such as combustion facilities and overfertilized soils (nitrogen oxides). Volatile organic compounds are generated by the use of solvents (including paints, varnishes, and adhesives) and by the combustion of fuel. Natural sources of precursor pollutants include emissions from deciduous and coniferous trees.

Indoors, ozone can be generated by electrical devices such as printers. High voltage and UV radiation are responsible for this.

Sensor used:

Ozone is measured using an electrochemical sensor. O₃ molecules that “bind” to the sensor’s surface cause a small current to flow through the sensor. The advantage of our sensor is that it is individually calibrated for sensitivity by the manufacturer and has an exceptionally long service life.

The ozone sensor we use exhibits cross-sensitivity to hydrogen sulfide (H₂S) and nitrogen dioxide (NO₂). Therefore, it also reacts to NO₂ and displays a deviation even in the absence of O₃. It reacts negatively to H₂S. If H₂S levels increase, the measured O₃ value decreases.

Ozone measurement:

The air-⁠Q is a versatile air quality monitor that also functions as an ozone monitor and can accurately measure ozone levels.

Here you can find a lot of information about the technology. You can order the air-⁠Q air analyzer from the online store.