Models of active galactic nuclei (AGNs) suggest that thermal material may exist within the central engine itself, on scales as small as 10^15^ cm. Relatively cool clouds could then reprocess part of the nonthermal continuum and affect the observed spectrum. This paper discusses the thermal and ionization equilibrium of dense clouds in very intense radiation fields. The numerical techniques and assumptions used to model this environment are described in detail, and test cases illustrating the approach to LTE are considered. Calculations show that clouds with densities >=10^14^ cm^-3^ could attenuate and harden the soft-medium-energy X-ray continuum, while simultaneously producing a thermal continuum in the infrared and optical regions. These effects are in the sense required to account for the observed infrared-X-ray continua of AGNs. A simplified treatment of thermal clouds within the continuum-forming region, suggested by the numerical calculations, is outlined. This should form the basis for further development of the theory of dense thermal clouds in AGNs.
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Ferland et al. (1988) studied this question.