Why UV-C Cannot Produce Ozone?

Date:Jan 13, 2021

Ultraviolet sterilization (UV-C) wavelength is an important factor for HVACR systems. By using sterilization energy to protect the refrigeration coil from microbial growth, facility managers also enjoy the benefits of reducing the spread of airborne infectious diseases. However, due to concerns about ozone, some facility managers may hesitate to use these benefits to realize their applications. The ultraviolet spectrum contains four independent wavelengths-UV-A, B, C and vacuum UV-each wavelength operates at a different energy level, and only one can produce ozone (vacuum UV). As shown in the figure below, vacuum ultraviolet rays work in the range of 100-200nm and can produce ozone. On the contrary, UV-C reaches the best bactericidal strength around 253.7nm. Since ozone can only be produced below 200nm, and as for the wavelength at 253.7nm (rounded to 254nm) or 265nm 275nm, it will not produce ozone. Undefined In addition to the stronger 254nm wavelength that does not produce ozone, UV-C lamps also provide another ozone protective layer. Most germicidal lamps, including those from UV Resources, are made of doped quartz glass, which blocks the transmission of the 185nm ozone wavelength. The doped quartz glass allows radiation of 253.7nm to pass, but prevents the 185nm wavelength from escaping. Therefore, germicidal lamps with doped glass will not produce ozone.




What is ozone? 

Ozone is present in low concentrations throughout the earth’s atmosphere. Some researchers said that this chemical "from high to high, from low to low." For example, if there is no ozone layer to protect the earth’s stratosphere, the sun’s ultraviolet radiation will make life on earth uninhabitable. However, at the street level, high concentrations of ozone are toxic to animals and plants. In humans, ozone can irritate the nasal passages, causing nausea, and prolonged exposure can cause lung inflammation. Ozone, also known as vacuum ultraviolet (UV-V), is a gas molecule that contains three (3) oxygen atoms-therefore, it has a destabilizing effect on oxygen in the air (leading to its irritation and danger to the human body) . UV lamps "tuned" to 185nm can produce ozone from oxygen (O2) by destroying O2 molecules and splitting them into two oxygen atoms. These two oxygen atoms try to connect to other oxygen molecules (O2). It is the attachment of this third oxygen atom that produces ozone (O3). The irony is that ultraviolet light with a wavelength of 240-315nm will destroy the third oxygen atom attached above and convert it back to oxygen. The ozone destruction peak occurs at a wavelength of 254nm. Therefore, UV-C lamps with a wavelength of 253.7nm will actually destroy ozone! ASHRAE has said that certain air filters produce ozone, so its position is to stop using "use of ozone-reactive equipment to clean the air."



For designated engineers, HVACR contractors and facility managers, keeping the building at the highest level of efficiency and maintaining its performance throughout the building’s life cycle is one of today’s major challenges. Nowadays, using sterilization technology, almost all HVACR systems can become potential candidates because it provides many proven operational advantages, including: (b) Restore and maintain heat transfer and airflow capabilities to a "built" state; (C) Greatly improve indoor air quality; (d) Reduce maintenance. Similarly, although UV-C technology has been proven to restore HVACR performance to its original capacity, designated engineers, HVACR contractors and facility managers can rest assured that the sterilization wavelength cannot produce ozone. In addition, the sterilization wavelength of 253.7nm will destroy ozone. Therefore, please keep ozone-free in the 254nm region.

Previous: Far UVC VS UVC

Next: Are there Limitations to UVC Disinfection?