The development of a patented polymer based electron emitting technology (EAC) has provided a means to study the impact of reduced bioload in stable air on productivity. Apart from capturing particles in a negatively charged electrostatic field operating over the entire stable with hundreds of meters of emitting structure, the electrons combine with oxygen and vapor to produce H2O2 to block mould metabolism. Before and after data from three egg producing farms with 20-50 000 free-roaming layers were collected as part of their standard productivity control. The number of mould colonies decreased from >7 (range 7 – 30) to single colonies. Lay percentage over the production period covering 22 to 75 weeks of age increased by 3% and the feed conversion improved by 9%. During the last 10 production weeks, the overall improvement in productivity was 27% enabling the farmers to maintain a high productivity despite an ageing population of layers.