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Breezy blocks

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Max von Pettenkofer (1818-1901) is a name to conjure with. A German chemist and hygienist, he is considered to be a founder of epidemiology, but is also known for his researches in the ventilation of dwellings, (as well as sewage disposal systems, with reference to the need to halt the spread of cholera).

1However, Fiedler and Lindner 2cast doubt on the value of his legacy.

They note that while he made valuable contributions to the development of hygiene in buildings, he 'has also been responsible for a number of decisive misconceptions, with after-effects well into the second half of the 20th century, ' (page 65). Most notably his lime-mortar and candle test, in which he inserted air-hardened lime into a tube, sealed around it with wax and blew air through one end, such that the breeze coming out of the other was sufficient to extinguish a candle. This was intended to demonstrate the permeability of building materials.

The passage of air through standard heavyweight building construction, manifesting itself as a breeze, is not the way it works, although Fielder and Lindner quote Reiner Mueller, director of hygiene at Cologne University as late as 1935, saying that 'bricks and other porous 2substances are so permeable that wind will slowly blow through unplastered walls, ' (page 66).

It was left to August Gaertner, Extraordinary Professor of Hygiene and Legal Medicine, and Pettenkofer's contemporary at the turn of the 20th century, to develop significant research into the role of ventilation and hygiene in buildings, analysing the role of pressure differentials and permeability.

With disarming simplicity (which belies the modern elevation of common sense into a science), Gaertner said that, 'since most people do not wish to discharge heat, which has a high price, ventilation is reduced to a minimum, ' (pages 67-68). He set a range of minimum ventilation rates to maintain comfort, health and well-being - even assessing the phenomenon of 'heat discharge perceived as draft' (page 66).

REFERENCES 1The Columbia Encyclopaedia , Sixth Edition,2001 2August Gaertner and building, housing and communal hygiene: 100 years of housing hygiene in Jena , Klaus Fiedler and Martina Lindner, International Journal of Hygiene and Environmental Health , Issue 203,2000

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