text: HO masers, a type of astrophysical maser, were the first masers to be discovered in space and have been observed in more environments than any other type of maser.
  In the Milky Way, HO masers are found in stellar masers (evolved stars), interstellar masers (regions of massive star formation), or in the interface between supernova remnants and molecular material. Interstellar HO masers are often observed from molecular material surrounding ultracompact H II regions (UC H II). But there are masers associated with very young stars that have yet to create UC H II regions. This class of HO masers appears to form near the edges of very dense material, places where HO masers form, and where total densities drop rapidly, and UV radiation from young stars can dissociate the HO molecules. So, observations of HO masers in these regions, can be an important way to probe the distribution of the important HO molecule in interstellar shocks at high spatial resolutions.
  Application in water purification
  Hydroxyl radicals also play a key role in the oxidative destruction of organic pollutants.