Non-thermal plasmas (NTPs), are sometimes called “cold flames” because they share many of the properties of fire - including the sterilizing properties. However, unlike flames, NTPs are not hot and do not consume oxygen.

NTPs are formed in the presence of a high electric field gradient, i.e., a substantial difference in voltage between two electrodes that are closely spaced. At very low pressures, well below that of ambient air, plasmas can form stably in various gases.  At standard atmospheric pressure, the same configuration would generate sparks that jump between the electrodes - not what we want.  However, if a dielectric material is situated between the electrodes, then a plasma that covers a much larger volume than a spark can be maintained stably over the surface. 

Combustion flames are thermal plasmas that are routinely used for sterilization. Like combustion flames, non-thermal plasmas (NTPs) produce energetic, highly reactive but also short-lived fragments of molecules.  However, unlike combustion flames, NTPs:

NTPs are quick and effective for reducing airborne pathogens.  Specifically for air that is flowing (such as in ventilation ducts), quick and effective translate to small in size.  This makes NTPs well-suited for miniaturization, such as for use in wearable devices. 

Existing air cleaning technologies can’t compete with the effectiveness, capacity, and compactness of NTPs, including some that are already being used in the fast-growing wearable air purifier market.