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History of ventilation! Part 1: What is the minimum ventilation rate?
August 20, 2014

History of ventilation! Part 1: What is the minimum ventilation rate?

The ventilation is not only about the ventilation system but also about the amount of the air for ventilating and created good thermal comfort. Read here about finding the suitable ventilation rates and in the next article read about development of ventilation system throughout the centuries.

The ventilation process started when man brought the fire into his home and discovered that it needs an opening in the roof to let the smoke out as well as the supply of the air for burning process. Because the fire created a more comfortable and warmed space, thermal comfort was linked to the ventilation.

In Egypt it was discovered that the stone carvers working indoors have more respiratory problems due to the dust than those working outdoors. This observation led to the finding that the improvement of air circulation for workers can be done with adding more openings in the walls.

In 1st century B.C., the need for indoor fires disappeared temporarily with Romans´ invention of underfloor heating creating sort of central heating system with hot combustion products and ducting around the periphery of a building from stoves through the floor tiles to a smokestack.

In Middle Ages, using open fires in fireplaces has led to smoke poisoning in closed and crowded rooms. King Charles I of England has declared in year 1600 that the ceiling height must be above 3 m and windows must be higher than wider in order to improve the smoke removal.

In 1775, the French chemist Antoine Lavoisier identified carbon dioxide (CO2) as a cause of bad air and he concluded that excess of CO2 rather than reduction of oxygen caused the sensation of stuffiness and bad air. In 1836, Thomas Tredgold published the first estimate of the minimum ventilation rate of 7.2 m3/h per occupant. This estimate was covering the metabolic needs of a human but did not take into account the needs for ventilation for comfort. During the Crimean war (1853-1855) the physicians recommended 50 m3/h per occupant of fresh air as an adequate level for comfort based on observation of faster disease spread among wounded soldiers in crowded hospitals with poor ventilation. The value of 14 l/s was accepted as a minimum ventilation rate in 1914 by the American Society of Heating and Ventilation Engineers (ASHVE).

After the energy crisis, half a century later this law was reviewed in order to minimize the indoor air rate and based on Danish and American studies it was confirmed that 27 m3/h per occupant was the minimum accepted volume of air. After modification of this value due to clothing, heating/cooling system design and living habits (i.e. smoking) it was published in 1989 in ASHRAE/ENSI Standard 621989.

This has not stopped the researchers in exploring the ventilation rates, thermal comfort and environmental aspects of ventilation.

Source: The History of Ventilation and Temperature Control by John E. Janssen, ASHRAE Journal, September 1999