During times when contamination is a huge priority, many dental professionals may be concerned what to do with poured gypsum models as well as printed ones.
It is true that, at least regarding gypsum models, the impression ideally should have been disinfected before entering the lab to be poured. In the case of a printed model, it would have most likely been printed from a file and would never have come in contact with the patient. However, once the models are produced by either method, they will be in contact with the dental staff during case fabrication. Cross contamination can be a concern inside and outside of the facility, especially if the models are to be shipped to other locations.
Gypsum models, once they have completely set at least one hour, can be lightly sprayed with 60% alcohol content or greater. This should have no degrading effect on the gypsum itself, providing the surface is not saturated (do not immerse the model in the alcohol solution). One thing you would not want to do with a gypsum model is heat treat it in an oven or autoclave. This will cause a breakdown of the crystalline structure of the gypsum and could cause erosion.
In regards to printed models, they can also be sprayed directly with an alcohol solution of 60% or greater. One thing to avoid is using a surface tension reducer after the alcohol treatment. It is especially important if the resin is going to be burned out to avoid surface irregularities in the casting. Some resins can be autoclaved but you should check with the manufacturer to be certain.