The answer to this question is not so easy because it depends on many factors (in addition to temperature and air flow, relative. humidity also the quality and character of the paper, the method of applying the emulsion, hardener content, etc.)

Recomendation from Foma Bohemia for temperature 20 degrees Celsius and relative humidity 40-60%.

minimum 10 hours when emulsion is applyed with brush.
minimum 6 hours when sprayed. 6 hours for each sprayed layer.

The point is that the emulsion dries not only on the surface. This would cause problems by the use of developer etc.
Given time can be shortened with a faster flow of dry air when you use hair dryers or the like.