AIR MONITORING
USE OF DEEP UV LEDS FOR HIGHLY ACCURATE OZONE MEASUREMENT IN INDUSTRIAL, SCIENTIFIC AND MEDICAL PRACTICE
Ozone is a strong oxidising agent that can cause respiratory irritation and respiratory diseases in humans and animals. The ozone layer in the stratosphere protects living organisms on Earth from damage caused by the sun’s high-energy ultraviolet radiation. Ozone is mainly used to disinfect water and air and to eliminate odours in areas such as swimming pools, sewage treatment, the food industry and fire damage. It also serves as a powerful bleaching agent in the paper industry and is used medically as ozone therapy. When used, ozone must always be produced on site and require special safety measures due to its irritating effect.
• Drinking water: Ozone is used to disinfect drinking water and eliminate trace substances.
• Wastewater: It is used to combat bacteria and convert poorly degradable substances into harmless substances. • Swimming pools: The use of ozone helps to disinfect swimming pool water. • Disinfection: Ozone can be used to disinfect air and surfaces to eliminate bacteria and viruses.
• Odour removal: It is used to remove odours after fire damage, in hotel rooms, in the fishing industry, in vehicles or in rubbish rooms.
• Bleaching agent: Ozone is an effective bleaching agent, which is mainly used in the paper industry to bleach paper pulp. • Textile industry: Ozone is also used as a bleaching agent in the textile industry.
• Ozone therapy: Medical applications include the treatment of circulatory disorders, viral infections or skin diseases.
Ozone O3 consists of three oxygen atoms and can therefore be produced directly from oxygen O2
(Eq. 1). This requires energy in the form of UV radiation or an electrical discharge. This energy ΔH is also referred to as the molar reaction enthalpy.
3O2 In 1839 Schönbein1 →2O3 ; ΔH=+286 kJ/mol (1) form can exist simultaneously in two different molecular forms, namely O3
first described the unique phenomenon whereby a chemical element in gaseous and O2
. However, ozone
spontaneously decomposes back into oxygen, with the half-life being highly dependent on the ambient temperature and possible reaction partners and catalytic surfaces [1].
Table 1. Half-life of ozone [1]
Temp. [°C] -50 -35 -25 20
120 250
1 Christian Friedrich Schönbein German Chemists and Physicists (1799-1864) 22 | AET NOVEMBER 2025 |
ENVIROTECH-ONLINE.COM
Half-life 3 months 18 days 8 days 3 days
1.5 hours 1.5 seconds
Fig.1: Spectral position of the individual O3 and merge continuously into one another.
absorption bands. The bands are not sharply separated from each other UV-Absorption Spectra
Ozone has a pronounced absorption spectrum with several sub-bands extending from 200 nm into the visible and NIR range. Fig. 1 shows the Hartley, Huggins, Chappuis and Wulff sub-bands. The strongest band is the Hartley band with a maximum at λ=255 nm, which is mainly used in trace gas analysis. The other bands can be used, for example, for high O3
ozone can be detected in the IR range due to its permanent dipole moment. Due to spectral overlaps, this spectral range is rarely used for O3
gas analysis.
Lambert-Beer Law The absorption of UV radiation occurs according to Lambert-Beer’s law. [5]. I=I0
exp.-[σ∙n∙L] (in cm2 molecule-1 ).
The following version has become established for practical applications. I(c)=I0
exp.-[α∙c∙L] With α = Coefficient of absorption in cm-1 (3) and c = Gas concentration in ppm (10-6 ). (2)
where I0 and I are the incident and transmitted light intensities, L is the absorption path length (in cm), n is the concentration of the absorber (in molecule/cm3
), and σ is the absorption cross section concentrations. However,
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