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Figure 4 image as featured in the Lectures on Ventilation.

The Importance of Opening the Windows and Some Amazing Images to Illustrate the Point


Lectures on Ventilation was published in the 19th century and, beyond being a breath of fresh air, it’s also looks out on some beautiful illustrations.

In 1865, some 40% of the population of Philadelphia would die due to dirty air. In Paris, Manchester, London and New York people got sick from tuberculosis because of the poor quality of the air that they breathed. According to the fascinating book Lectures on Ventilation (Lewis W. Leeds, 1868) this was due to the fact that, in addition to the construction of crowded buildings, traffic and the proliferation of factories extinguished oxygen and exchanged it for carbon dioxide, people spent too much time enclosed in unventilated spaces. After multiple tests of carbonic acid in the air, scientists discovered that the most lethal air of all was the “their own breath.” That is, the breath of those who worked long hours closed in factories and offices. And there were many. This is why the cure for tuberculosis was always to head for the country for a season. The author of Lectures explains:

The reason why cities are so much more harmful than the country, is not because the air in the street is so much more impure, but because the houses are built together that this vast ocean of air cannot get at and through them to purify them as it does in the houses in the country.

Thus, the scavengers and vagabonds of large cities were considerably healthier than the working classes of the time. Remember the wonderful essay by Benjamin Franklin on the importance of sleeping with the windows open in order to encourage “sweet dreams.” This was the same sentiment in which Lewis wrote his own book; that many people died because of “their own breath.” Even today, Lectures on Ventilation is a curious testimony on the quality of air people were breathing some 150 years ago, and on the importance of air (which should be in our minds of course). The illustrations accompanying the book are truly beautiful. They present an unintentionally aesthetic testimony that might even be understood as a breath of fresh air.


Figure 3 as featured in Lectures on Ventilation.


Figure 3 as featured in Lectures on Ventilation.


Figure 1 as featured in Lectures on Ventilation.


Figure 5 as featured in Lectures on Ventilation .


Figure 6 as featured in Lectures on Ventilation.


Figure 4 as featured in Lectures on Ventilation.


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