A propellant conditioning assembly, for providing a propellant feed to a medical dosing device filling apparatus, the assembly comprising: an input conduit to receive a propellant at a constant pressure from a propellant reservoir; a bifurcation to divide the input conduit into first and second conditioning conduits, the first conditioning conduit including a cooler device to selectively cool a diverted first propellant stream flowing through the first conditioning conduit, and the second conditioning conduit including a heater device to selectively heat a diverted second propellant stream flowing through the second conditioning conduit; and an output conduit to receive the first and second propellant streams, the relative proportion of the first and second propellant streams merging in the output conduit being controlled to regulate the temperature of a merged constant pressure propellant feed exiting from the output conduit, wherein the input conduit includes an input temperature sensor arranged to measure an input temperature of the propellant in the input conduit, the measured input temperature being used to control the selective operation of the cooler and heater devices, wherein the first conditioning conduit includes a first flow control valve to control the flow rate through the first conditioning conduit and the second conditioning conduit includes a second flow control valve to control the flow rate through the second conditioning conduit, wherein the output conduit includes an output temperature sensor arranged to measure an output temperature of the merged constant pressure propellant feed in the output conduit, the measured output temperature being used to control the operation of the first and second flow control valves, and wherein the input conduit includes an input flow rate sensor to measure the flow rate of the propellant through the input conduit. an input conduit to receive a propellant at a constant pressure from a propellant reservoir; a bifurcation to divide the input conduit into first and second conditioning conduits, the first conditioning conduit including a cooler device to selectively cool a diverted first propellant stream flowing through the first conditioning conduit, and the second conditioning conduit including a heater device to selectively heat a diverted second propellant stream flowing through the second conditioning conduit; and an output conduit to receive the first and second propellant streams, the relative proportion of the first and second propellant streams merging in the output conduit being controlled to regulate the temperature of a merged constant pressure propellant feed exiting from the output conduit, wherein the input conduit includes an input temperature sensor arranged to measure an input temperature of the propellant in the input conduit, the measured input temperature being used to control the selective operation of the cooler and heater devices, wherein the first conditioning conduit includes a first flow control valve to control the flow rate through the first conditioning conduit and the second conditioning conduit includes a second flow control valve to control the flow rate through the second conditioning conduit, wherein the output conduit includes an output temperature sensor arranged to measure an output temperature of the merged constant pressure propellant feed in the output conduit, the measured output temperature being used to control the operation of the first and second flow control valves, and wherein the input conduit includes an input flow rate sensor to measure the flow rate of the propellant through the input conduit.