An additive manufacturing machine may include a beam source, a process chamber, a beam column operably coupled to the process chamber and/or defining a portion of the process chamber, and a gaseous ionization detector disposed about the beam column. The gaseous ionization detector may be configured to detect elementary particles corresponding to an ionizing gas ionized by an energy beam from the beam source. A method of additively manufacturing a three-dimensional object may include determining data from a gaseous ionization detector disposed about a beam column of an additive manufacturing machine, and additively manufacturing a three-dimensional object using the additive manufacturing machine based at least in part on the data from the gaseous ionization detector. A computer-readable medium may include computer-executable instructions, which when executed by a processor associated with an additive manufacturing machine, cause the additive manufacturing machine to perform a method in accordance with the present disclosure.