Mark1 carriage window Originally uploaded by seadipper . These sliding ventilators came into use in the 1930s. They were an advanced design with an aerofoil to deflect the air flow over the moving train and provide draught-free ventilation if they are opened up to the black marks on the notice above the warning sign. If the weather is hot and you want a good blow, you open them all the way. Unlike air conditioning, they do not consume a lot of power, are inexpensive to install and maintain, and do not break down when they are most needed, in the middle of the summer. They also have the advantage of letting some steady ambient noise into the train which drowns out the annoying sounds of mobile phones, personal stereos and loud conversations, so you can blank it out and concentrate on what you are doing. I suspect they are more hygienic than air conditioning - I have always wondered what life-forms live in the ducting. Unfortunately, some bright spark though that hopper ventilators (win...
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