The formula HO2 represents the radical compound hydroperoxyl, according to the NASA Goddard Earth Sciences Data and Information Services Center. Hydroperoxyl is also known as perhydroxyl radical.
The compound is formed when a single hydrogen atom bonds to molecular oxygen, or O2, hence the chemical formula HO2. Hydroperoxyl is extremely reactive, which makes it useful as a cleanser in toxic environments where it cleanses the air of organic pollutants. Unfortunately, hydroperoxyl is also known conclusively to cause atmospheric breakdown of the ozone layer in the Earth's stratosphere, which continues to cause climate change as of 2014. For this reason, its use is limited.