Cosmogenic nuclide geochronology requires accurately scaling production rates with altitude. The energy spectrum of cosmic radiation changes with altitude, and reactions that are sensitive to different energies may have different scaling behavior. Here, we model the altitude scaling of ³⁶Cl production from Fe and evaluate this model against calibration data. The data are broadly consistent with the prediction of larger-altitude scaling factors for ³⁶Cl from Fe than for other reactions.