There has been a great deal of discussion in recent years of the merits of "low charge" systems. The incentives to follow this trend are diverse, ranging from the flammability of hydrocarbons or the toxicity of ammonia to the expected higher cost of the new fluids currently under development and not yet on the market. New technology has provided a further boost to the aspirations of system designers. Microchannel heat exchangers and innovative sensor technology enable plants to run on a fraction of the charge that was required back in the olden days when refrigerant was cheap and leaks didn't seem to matter. Andy talks about the pros and cons of the new technologies.