Chlorine dioxide (ClO2) is a yellow-green gas with an odor similar to chlorine. It is very different from elemental chlorine, both in its chemical structure and in its behavior. The molecule ClO2 has an odd number of valence electrons, and therefore, it is a paramagnetic radical.
The boiling point of chlorine dioxide is 11°C. In normal atmospheric conditions, it’s always present as a gas. It’s concentration is not affected by temperature or humidity. Due to its gaseous nature, it has excellent distribution, penetration and sterilization abilities.
As can be seen in the chart above, the size of a chlorine dioxide gas molecule is 0.124 nm, much smaller than microorganisms and viruses, allowing the gas to easily penetrate into any areas where these microorganisms might be concealed.
Compounds within the cells and on the surface of cell membranes that contain oxidizable material like amino acids, react with chlorine dioxide, causing cell metabolism to be disrupted. Until today, no micro-organism has shown resistance to a proper chlorine dioxide treatment. Information on tested organisms can be found in the Biological Efficacy List. This list is constantly updated as testing is constantly ongoing. If a micro-organism is not on the list, it doesn’t mean chlorine dioxide isn’t effective against.