Dear engineers and scientists, Measuring and artificially producing hydroxyl radicals is relatively new research with great challenges due to short half life. I have asked this question on many forums to gather as much information as I can and my question is: How can we measure hydroxyl radical concentration? I am only interested in airborne concentration, hydroxyls in water and cells are not relevant to my research. Also there are few articles mentioned every time in these type of discussions and they are: 1) A Novel High-Throughput Approach to Measure Hydroxyl Radicals.... by Yeongkwon et al (2015) - the authors use different types of probes and fluorescence spectroscopy techniques to measure the OH radicals. 2) Hydroxyl Radicals in the Tropical Troposphere.... by Martinez et al (2010) - the authors use a device called HORUS mounted to an aircraft but using the fluorescence technique too. Specifically, by exciting the OH radical and then measuring decaying fluorescence of the excited molecule. Molecular probes and associated machinery, fluorescence detection equipment are all very expensive and I can not afford to buy them. So, it boils down to two remaining questions in my research: 1) Are there any facilities in Australia (preferably in NSW) that I can use to get few results? 2) Are there any ideas (tested or non-tested) or suggestions to build my own measuring equipment (economical) such as HORUS used in Article No. 2? HORUS is not economical but I am implying custom made. Any other relevant research paper/patent/article/comment you may want to direct me to, will be appreciated. All suggestions and help is much appreciated.