Lecture_3b_Indoor_Air_Quality

Lecture_3b_Indoor_Air_Quality - 10/25/2008 2- Indoor Air...

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10/25/2008 1 Ventilation Requirements 2- Indoor Air Quality IAQ y “Sick Building Syndrome”???? {Lack of fresh Air} y Poor indoor air quality affects people in many ways: 1- Comfort: Stuffy, odorous environment 2- Acute health effects: burning eyes, chest symptoms, transmission of viruses. 3- Chronic health effects. 4- Direct link between IAQ and productivity
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10/25/2008 2 Major factors for sick buildings y Lack of fresh air and poor ventilation y Externally generated pollution from vehicle emission. y Pollution from process discharge, building ventilation exhaust, boiler flues carried inside by ventilation air. y Internal sources: furnishing, occupants, equipment, ect. Most common pollutants are odors, CO 2 , formaldehyde, tobacco smoke, volatile organic components and aerosols. High concentration of h2O vapor. y Ground: radon, methane, etc. Problems of IAQ arized from 1- Increase in building air tightness. 2- Reduction in ventilation reduces energy consumption 3- Increase in the use of computers, printers, copiers and other office equipment. 4- Increased use of textile floor covering 5 Id f A C 5- Increased use of AC 6- Lack of maintenance
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10/25/2008 3 Olfactory Stimuli y The human olfactory system is usually superior to existing contaminant concentration measuring instruments and it can detect minute concentration levels that are sometimes undetectable by instruments. y The olfactory receptors which are sensitive to odorants are located in the upper nasal passages, i.e. the olfactory cleft. The surrounding tissues in the nasal passages contain other receptors that respond to airborne vapors, the so-called common chemical sense. These receptors or nerve endings are stimulated by vapors. y For all practical purposes, olfaction and the common chemical sense operate as a single perceptual system. y The olfactory receptor are connected to the olfactory bulb in the brain which coordinates the passage of information it receives from the receptors to other regions of the body. Olfactory Stimuli y The perception of odorant by people is subjective and it is therefore difficult to define threshold limits for odors. y The quality of air is usually determined by people's sensation to various odors present in the air. y Most organic substances are olfactory stimuli but only a few inorganic substances are. y Therefore, any subjective evaluation of the air quality using human olfaction will not include all sources of pollution. Some very harmful pollutants, e.g. carbon monoxide and radon, cannot be perceived by people even at high concentrations. The sensitivity of the human olfactory system to odor perception has been utilized by Fanger in developing a new approach for evaluating the intensity and concentration of pollutants.
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10/25/2008 4 Intensity and concentration of pollutants y The relation between perceived odor intensity, s, and odor concentration, c, is in the form of the following power law y C is concentration in ppm.
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Lecture_3b_Indoor_Air_Quality - 10/25/2008 2- Indoor Air...

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