ABSTRACT
In hypogean monuments of tourist interest, microenvironmental transformations due to the incidence of visitors and management infrastructures can cause substantial processes of deterioration affecting the cultural heritage. The proper management and preservation of these monuments includes an adequate regulation of tourist visits that must be based on precise scientific studies of the environmental effects and risks (Albertano et al. 2003). Roman catacombs are hypogean monuments included in a tourist package attracting more than 500,000 visitors per year. Areas
receiving visits are exposed to intense alteration from both the ingress of visitors and the conditioning of the galleries (lamps, ventilation, openings to the exterior, doors and panels, etc.). The catacombs were built between the second and seventh centuries AD, and are considered among the greatest and most important monuments of Rome. St. Callixtus catacombs are part of a cemeterial complex with a network of galleries about 20 km long, distributed in four levels, and with a depth of more than 20 metres. Some of the cubicles and passages of this network have more than six metres in height and sometimes reach the land surface, allowing air circulation. The original entrances
are present only at the first level, with communications between the different floors. However, the recent installation of an air ventilation system has connected the lower levels of the catacombs with the outside atmosphere.
