A system for manufacturing three dimensional objects can include logic to detect, for at least one vessel, a moisture content level corresponding to a build material residing in the at least one vessel. The logic can also adjust a humidity level and a temperature of a gas and a conditioning agent applied to the at least one vessel, wherein the humidity level and the temperature are based on the moisture content level and a temperature of the build material residing in the at least one vessel. Additionally, the logic can initialize manufacturing a three dimensional object with the build material from the at least one vessel in response to detecting the moisture content level of the build material residing in the at least one vessel is within a predetermined range.