  The uncertainty in the absolute value of the air-fluorescence yield still
puts a severe limit on the accuracy in the primary energy of ultra-high-energy
cosmic rays. The precise measurement of this parameter in laboratory is in turn
conditioned by a careful evaluation of the energy deposited in the experimental
collision chamber. In this work we discuss on the calculation of the energy
deposition and its accuracy. Results from an upgraded Monte Carlo algorithm
that we have developed are compared with those obtained using Geant4, showing
excellent agreement. These updated calculations of energy deposition are used
to apply some corrections to the available measurements of the absolute
fluorescence yield, allowing us to obtain a reliable world average of this
important parameter.
