Instabilities can be both triggered and quenched by chemical releases which generate ionospheric holes. Vapors, such as H2O, H2, and CO2, rapidly react with the O+ ions in the upper atmosphere, producing polyatomic ions such as H2O+, H3O+, OH+ an O2+. These ions quickly combine with electrons, leaving natural species. The enhanced F region neutralization initially tends to quench the fluid instabilities in the modified region. After the injected vapors dissipate, chemical quenching becomes unimportant. At late times, the sides of the ionospheric hole may become unstable to fluid instabilities. The wind-driven gradient-drift instability, the current-convective instability, and the gravitational Rayleigh-Taylor instability are three classes of instabilities which may produce irregularities in ionospheric holes. These instabilities are investigated by using local, linear perturbation analysis. The removal of preexisting plasma irregularities by reactive chemical releases is also investigated.