A survey of the data on measured particle fluxes and the rate of ionization in the atmosphere is presented. Measurements as a function of altitude, time and cut-off rigidity are compared with simulations of particle production from cosmic rays. The s
imulations generally give a reasonable representation of the data. However, some discrepancies are found. The solar modulation of the particle fluxes is measured and found to be a factor 2.7$pm$0.8 greater than that observed for muons alone near sea level.
