Atmospheric pressure plasmas are frequently considered to be in local
thermodynamic equilibrium due to the high frequency of collisional pro
cesses which drive the plasma state towards a Maxwell-Boltzmann equili
brium. However, various forms of thermodynamic, ionizational, and chem
ical nonequilibrium have been demonstrated and investigated in atmosph
eric pressure plasma environments over the last several years, and the
nonequilibrium behavior of such systems can be quite significant. The
investigation, understanding, and exploitation of atmospheric pressur
e nonequilibrium plasma chemistry is necessary to the further expansio
n of plasma-based systems into mainstream manufacturing and processing
applications. Several experimental programs to investigate the fundam
ental processes of atmospheric pressure nonequilibrium plasma chemistr
y, and the application of this nonequilibrium to various chemical syst
ems have been undertaken in our laboratories. The results of these inv
estigations have shed light on the kinetics behind various forms of at
mospheric pressure nonequilibrium chemistry, and provided insights int
o the beneficial control of nonequilibrium plasma chemistry for proces
sing applications.