It throws up some interesting facts - that the Welsh ban was forecast to save 400-600 lives a year, but the most important factoid is the following statement:
'The British Medical Association (BMA) claimed that ventilation cannot protect against the health risk of passive smoking. They advised the Committee that ventilation does not remove the fine particulate matter that is breathed most deeply into the lungs and into the thorax and that filtered tobacco smoke has the same potential to ncause cancer in a cell system as unfiltered tobacco smoke. Their view was supported by, among others, the Chartered Institute of Environmental Health, the Public HealthAssociation Cymru and Ash Wales. Ash Wales and Professor Gerard Hastings contended that it would take an air flow comparable to a wind tunnel or tornado to be in any way effective.' [emphasis added]
Which kinda puts the mockers on John's ill-conceived plan. Remember also that any toxic particulates removed by extraction will be dragged over the heads of the assembled drinkers in any case. Further damage to the concept comes from a comment on another blog, which put the cost of the extraction systems at somewhere north of £20,000 apiece - hardly worthwhile for most pubs or restaurants (and taking no account of the design of the existing buildings, some of which are listed buildings).
Back to the drawing board, John. Again.