Document 44dG7X1MnRZxRZORLQJVjKd6Q

of and 1937American Society Heating Ventilating Engineers Guide, SECTION V--AIR QUANTITY The quantity of air used to ventilate the given space during occupancy shall always be sufficient to maintain the standards of air temperature, air quality, air motion and air distribution as herein required. Not less than 10 cu ft per minute per occupant of the total air circulated to meet these requirements shall be taken from an outdoor source. APPENDIX Table A. Effective Temperatures Ranging from 64 Deg to 69 Deg for Various Dry-Bulb Tem peratures and Relative Humidities for Still Air for Persons Normally Clothed and Slightly Actives (For use when heating or humidification is required) Temperatures (Deg Fahr) 30 Relative Humidities (Per Cent) 35 40 45 50 55 Effective Temperatures (Degrees) 60 67 64.0 64.3 68 64.0 64.2 64.5 64.8 65.1 69 64.1 64.4 64.8 65.1 65.4 65.7 66.0 70 64.8 65.1 C5.4 65.8 66.2 66.5 66.85 71 65.5 65.8 66.2 66.6 67.0 67.3 67.7/7 72 66.2 66.5 66.9 67.3 67.7 68.1 68 &/ 73 67.0 67.3 67.7 68.1 68.5 68.9 \- 74 67.7 68.0 68.4 68.8 75 68.4 68.7 76 69.0 See Fig. 6. Table B. Effective Temperatures Ranging from 69 Deg to 73 Deg for Various Dry-Bulb Tem peratures and Relative Humidities for Still Air for Persons Normally Clothed and Slightly Active-** (For use when cooling or dehumidification is required) Temperatures (Dec Fahr) 30 Relative Humidities (Per Cent) 35 40 45 50 55 Effective Temperatures (Degrees) 60 73 69.3 74 69.3 69.7 70.1 75 69.1 69.5 70.0 71.5 71.0 76 69.0 69.4 69.9 70.5 70.8 71.3 71.8 77 69.7 70.2 70.7 71.2 71.6 72.1 72.0 78 70.4 70.9 71.4 71.9 72.4 73.0 79 71.1 71.6 72.2 72.6 80 71.8 72.4 72.9 81 72.5 See Fig. 6. bThis table applies primarily to cases in which the human body has reached equilibrium with the sur rounding air. A higher plane of summer effective temperatures is required in places of public assembly where the period of occupancy is short, than is required for offices and industrial plants where the period of occupancy is of longer duration. When the period of occupancy is two hours or less, the dry-bulb tempera ture shall be 72 F plus one-third of the difference between the outside dry-bulb temperature and 70 F, and the relative humidity shall not exceed 60 per cent. (See also Table 2.) - Definitions For the purposes of these standards the terms used shall be defined as follows:-- Ventilation: The process of supplying or removing air by natural or mechanical means, to or from any space. Such air may or may not have been conditioned. (See Air Conditioning). Air Conditioning: The simultaneous control of all or at least the first three of those factors affecting both the physical and chemical conditions of the atmosphere within any structure. These factors include temperature, humidity, motion, distribution, dust, bacteria, odors, toxic gases, and ionization, most of which affect in greater or lesser degree human health or comfort. 3 AChapter --Physical and Physiological Principles of ir Conditioning rw.Bulb Temperature: The temperature of the air which is indicated by any type of thermometer bichis not affected by the water vapor content or relative humidity of the air. W n.ist- Solid material in a finely divided state, the particles of which are large and heavy enough to fall th increasing velocity, due to gravity in still air. For instance, particles of fine sand or grit, such as are blown on a windy day, the average diameter of which is approximately 0.01 centimeter, may be called dust. Effective Temperature: An arbitrary index of the degree of warmth or cold felt by the human body i^oonse to temperature, humidity, and movement of the air. Effective temperature is a composite which combines the readings of temperature, humidity, and air motion into a single value. The mirical value of the effective temperature scale has been fixed by the temperature of saturated air which Tnducra an identical sensation of warmth. Humidity: The water vapor (either saturated or superheated steam) occupying any space, which may or may. not contain other vapors and gases at the same time. Relative Humidity: A ratio, although usually expressed in per cent, used to.indicate the degree of saturation existing in any given space resulting from the water vapor present in that space. The presence of air or other gases in the same space at the same time has nothing to do with the relative humidity of the space, which depends merely on the temperature and partial pressure of the vapor. Spaces In Which the Only Source of Contamination is the Occupant: . Spaces in which the atmospheric contamination results entirely from the respiratory processes of the occupant, including heat, moisture, and odors given off by the body. No manufacturing or industrial processes or other sources of atmospheric contamination, including heat and moisture, than people are considered under this title. RECIRCULATION AND OZONE The amount of recirculated air may be varied to suit changes in weather and seasonal requirements, so as to conserve heat in winter and refrig eration in summer, but the saving in operating cost should not be obtained at tfie expense of air quality. Ozone has been used for deodorizing recirculated air by oxidation or masking. Under favorable conditions* some success is possible but from the practical standpoint it is difficult to regulate the ozone output so as to just neutralize undesirable odors at all times during the occupancy of a room.. The difficulties appear to be mainly due to a wide variability in the rate of ozone disappearance in different rooms, or in the same room at different times, according to the characteristics of a room, the absolute humidity, impurities in the air, number and type of occupants, and probably other factors which require considerable study before ozone can be safely and economically applied. The allowable concentrations in the breathing zone are very small, between 0.01 to 0.05 parts of 03 per million parts of air. These are much too small to influence bacteria. Higher concentrations are associated with a pungent unpleasant odor and cpnsiderable discomfort to the occupants. One part per million causes respiratory discomfort in man-, headaches and depression, lowers the metabolism, and may even lead to coma48. Toilets, kitchens, and similar rooms, in buildings using recirculation, should be ventilated separately by mechanical exhaust in order to prevent objectionable odors from diffusing into other parts of the building. PROBLEMS IN PRACTICE 1 What is the purpose of conditioning the air of occupied rooms? Chiefly comfort, to be secured by control of temperature, humidity, air distribution, and body odors in the air. Other factors have yet to be studied. ^ What are the most comfortable air conditions? Comfort standards are not absolute, but they are greatly affected by the physical con dition of the individual, and the climate, season, age, sex, clothing, and physical activity, ror the northeastern climate of the United States, the conditions which meet the require- "Tfe British Medical Journal. Editorial. June 25,1932, p. 1182. See also Loc. Cit. Note 6.