ASHRAE Journal - February 2011 - 35

to absorb oxygen. Today we know that his theory was also incorrect. When the human body encounters higher levels of carbon dioxide than are present in normal air, it compensates by an increase in respiration rate. Still, Lavoisier’s theory predominated in physiological circles for about 100 years. One of the earliest texts which was an often-quoted source of ventilation theory is The Principles of Warming and Ventilating Public Buildings and Dwelling Houses by Tredgold1 published in 1836. The author expresses the belief that there are foul exhalations in the air, which are given off at each breath by individuals. It was concluded at this time already, in experiments by Priestly and Gay Lassac, that there was no chemically detectable difference between indoor (foul) air, and outdoor (healthful) air. Therefore some substance or substances which the analytical chemists could not detect were causing the air to become contaminated. This theory was commonly accepted because there was overwhelming empirical evidence that inhabitants of particular geographic districts showed “weak constitutions” and “pale visages,” which were attributed to this foul air. Rather than a lack of ventilation it was, as mentioned earlier, overcrowding and rudimentary sanitary facilities, providing an excellent environment for the spread of the numerous contagious diseases, which were responsible for the unhealthful condition. Nevertheless, believing that the human exhalations were the cause of the problem, an attempt was made to remedy the situation by supplying what was believed to be sufficient quantities of fresh air to preclude potentially toxic levels from developing. Using contemporary physiological knowledge and data, Tredgold proceeded as follows. He reasoned that if 32 cu in. of oxygen were consumed each minute, then the oxygen was replaced by an equal volume of carbon dioxide. Believing that the total amount of carbon dioxide in the exhaled air must be purged to ensure a healthful environment, it was a simple matter to calculate the gross amount of respired air which was contaminated by the carbon dioxide. This amount was calculated to be:
40 cu in. respired air respiration × 20 respirations min =

Ventilation Practices Evolved
By Dennis Stanke, Fellow ASHRAE, Chair of Standard 189.1 and Former Chair of Standard 62.1 Throughout the 1800s, disagreeable odors produced by people in high-occupant-density areas were linked to health. Prescribed ventilation rates rose steadily in this period, up to 30 cfm/person or more by 1900. Although linking human odors to health was probably reasonable (bioeffluent includes odor, virus and bacteria), studies in the early 1900s seemed to show that temperature and humidity had more impact on health than odors. So, the focus of ventilation shifted from health to odor-comfort; minimum outdoor airflow rates dropped to between 10 and 15 cfm/person based on studies in the 1930s, and that’s about where they stood when ASHRAE Standard 62-1973 was published. Ventilation practice has continued to evolve, but not merely in terms of engineering techniques. Basic ventilation theory now recognizes that the constituency (i.e., “quality”) of the indoor air has both comfort and health implications, and that indoor contaminants from both people and materials contribute to indoor air constituency. Outdoor airflow rates and procedures currently prescribed by Standard 62.1 help to ensure acceptable indoor air quality by accounting for contaminants due to both occupants and material emissions. In the past, ventilation for indoor air quality focused on either health impacts or odor-comfort. But today, prescribed outdoor airflow requirements address both health impacts and odor-comfort.
18 grains / min 6 grains / cu ft
= min

(Body moisture given off per min) (Absorbed by ventilating air)

3 cu ft ventilation air

800 cu in. respired air min

Therefore, if 800 cu in. of fresh air were supplied each minute, it would be sufficient to purge the vitiated 800 cu in. of respired air which contained the carbon dioxide. In addition to the above quantity of fresh air required to purge carbon dioxide, additional air is needed to remove the body moisture constantly given off at the rate of approximately 18 grains per min. At 60°F, Tredgold calculated it would require 3 cfm of fresh air to accomplish moisture removal. This 3 cu ft figure appears to be low since saturated air at 60°F contains approximately 6 grains of water per cu ft. Calculating:
February 2011

But this assumes the ventilating air can absorb 6 grains of moisture per cu ft which implies that the ventilating air contained little or no moisture on entering, an unrealistic situation at best. Finally, he concludes that ¼ cu ft of air is required to supply oxygen for candles and/or lamps which might be present. Summing up to get the total fresh air requirement yields: Carbon dioxide dilution = 800 cu in. / min. Body moisture removal at 3 cfm = 5,184 cu in. / min. Oxygen demand of candles and lamps at ¼ cfm = 432 cu in. / min. 64,163 cu in./min (equals appox. 4 cu ft.)
ASHRAE Journal 35



ASHRAE Journal - February 2011

Table of Contents for the Digital Edition of ASHRAE Journal - February 2011

ASHRAE Journal - February 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Thermal Coupling of Cooling and Heating Systems
10 Common Problems in Energy Audits
Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
A Guide to Wireless Technologies
Building Sciences
Solar NZEB Project
Emerging Technologies
People
Special Section
InfoCenter
Commissioning
Products
Washington Report
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2011 - ASHRAE Journal - February 2011
ASHRAE Journal - February 2011 - Cover2
ASHRAE Journal - February 2011 - 1
ASHRAE Journal - February 2011 - 2
ASHRAE Journal - February 2011 - Contents
ASHRAE Journal - February 2011 - Commentary
ASHRAE Journal - February 2011 - 5
ASHRAE Journal - February 2011 - Industry News
ASHRAE Journal - February 2011 - 7
ASHRAE Journal - February 2011 - Letters
ASHRAE Journal - February 2011 - 9
ASHRAE Journal - February 2011 - 10
ASHRAE Journal - February 2011 - 11
ASHRAE Journal - February 2011 - 12
ASHRAE Journal - February 2011 - 13
ASHRAE Journal - February 2011 - 14
ASHRAE Journal - February 2011 - 15
ASHRAE Journal - February 2011 - Meetings and Shows
ASHRAE Journal - February 2011 - 17
ASHRAE Journal - February 2011 - Thermal Coupling of Cooling and Heating Systems
ASHRAE Journal - February 2011 - 19
ASHRAE Journal - February 2011 - 20
ASHRAE Journal - February 2011 - 21
ASHRAE Journal - February 2011 - 22
ASHRAE Journal - February 2011 - 23
ASHRAE Journal - February 2011 - 24
ASHRAE Journal - February 2011 - 25
ASHRAE Journal - February 2011 - 10 Common Problems in Energy Audits
ASHRAE Journal - February 2011 - 27
ASHRAE Journal - February 2011 - 28
ASHRAE Journal - February 2011 - 29
ASHRAE Journal - February 2011 - 30
ASHRAE Journal - February 2011 - 31
ASHRAE Journal - February 2011 - 32
ASHRAE Journal - February 2011 - 33
ASHRAE Journal - February 2011 - Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
ASHRAE Journal - February 2011 - 35
ASHRAE Journal - February 2011 - 36
ASHRAE Journal - February 2011 - 37
ASHRAE Journal - February 2011 - 38
ASHRAE Journal - February 2011 - 39
ASHRAE Journal - February 2011 - 40
ASHRAE Journal - February 2011 - 41
ASHRAE Journal - February 2011 - 42
ASHRAE Journal - February 2011 - 43
ASHRAE Journal - February 2011 - A Guide to Wireless Technologies
ASHRAE Journal - February 2011 - 45
ASHRAE Journal - February 2011 - 46
ASHRAE Journal - February 2011 - 47
ASHRAE Journal - February 2011 - 48
ASHRAE Journal - February 2011 - 49
ASHRAE Journal - February 2011 - Building Sciences
ASHRAE Journal - February 2011 - 51
ASHRAE Journal - February 2011 - 52
ASHRAE Journal - February 2011 - 53
ASHRAE Journal - February 2011 - 54
ASHRAE Journal - February 2011 - 55
ASHRAE Journal - February 2011 - 56
ASHRAE Journal - February 2011 - 57
ASHRAE Journal - February 2011 - 58
ASHRAE Journal - February 2011 - 59
ASHRAE Journal - February 2011 - 60
ASHRAE Journal - February 2011 - 61
ASHRAE Journal - February 2011 - Solar NZEB Project
ASHRAE Journal - February 2011 - 63
ASHRAE Journal - February 2011 - 64
ASHRAE Journal - February 2011 - 65
ASHRAE Journal - February 2011 - 66
ASHRAE Journal - February 2011 - 67
ASHRAE Journal - February 2011 - 68
ASHRAE Journal - February 2011 - 69
ASHRAE Journal - February 2011 - Emerging Technologies
ASHRAE Journal - February 2011 - 71
ASHRAE Journal - February 2011 - 72
ASHRAE Journal - February 2011 - 73
ASHRAE Journal - February 2011 - 74
ASHRAE Journal - February 2011 - 75
ASHRAE Journal - February 2011 - People
ASHRAE Journal - February 2011 - 77
ASHRAE Journal - February 2011 - InfoCenter
ASHRAE Journal - February 2011 - 79
ASHRAE Journal - February 2011 - 80
ASHRAE Journal - February 2011 - 81
ASHRAE Journal - February 2011 - 82
ASHRAE Journal - February 2011 - 83
ASHRAE Journal - February 2011 - 84
ASHRAE Journal - February 2011 - 85
ASHRAE Journal - February 2011 - Commissioning
ASHRAE Journal - February 2011 - 87
ASHRAE Journal - February 2011 - 88
ASHRAE Journal - February 2011 - 89
ASHRAE Journal - February 2011 - 90
ASHRAE Journal - February 2011 - Products
ASHRAE Journal - February 2011 - Washington Report
ASHRAE Journal - February 2011 - Classified Advertising
ASHRAE Journal - February 2011 - 94
ASHRAE Journal - February 2011 - 95
ASHRAE Journal - February 2011 - Advertisers Index
ASHRAE Journal - February 2011 - Cover3
ASHRAE Journal - February 2011 - Cover4
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