1,721,037 research outputs found
Effects from Exposures to Human Bioeffluents and Carbon Dioxide
No full textThis chapter summarizes information published to date on the effects of human bioeffluents and carbon dioxide (CO2) on cognitive performance. Few studies have been carried out in this domain. They used simulated office tasks such as mathematical calculation and proof-reading and highly demanding cognitive tasks such as decision-making tests and simulated flights to examine the effects on cognitive performance. Concerning the effects of bioeffluents, the literature shows that the performance of simulated office work was reduced at CO2 levels above 3000 ppm; at CO2 levels between 1600 ppm and 3000 ppm, the effects have been observed; below 1600 ppm, no effects were observed. For highly demanding tasks, the effects were seen at the CO2 level of 950 ppmand over. Concerning the effects of pure CO2, it was shown that highly demanding tasks were affected at the levels at and over 1000 ppm; however, the results were inconsistent in the published studies, some showing no effects above 1000 ppm; for the tasks simulating office work, incidental effects were seen at CO2 level of 1200 ppm and 3000 ppm and no effects until 20,000 ppm, and even higher concentrations. These results require validation in future experiments, and mechanisms underlying the observed effects need to be delineated, especially since studies with human cells, ex vivo, indicate physiological impacts at the levels of 1000 ppm and higher, above the background level of CO2. Potential confounders also need careful examination, and they include, among others, an accurate exposure control, quality of cognitive performance measures, population diversities, and the length of exposure
Effects of Classroom Air Quality on Learning in Schools
No full textThis chapter describes the evidence of the effects of indoor air quality (IAQ) on learning of children and gives an overview of the size of the effects expected. The results from the published experiments on the effects of classroom air quality on the performance of schoolwork do confirm that these effects are systematic and show that improving classroom air quality will have a significant positive effect on some aspects of learning, both on cognitive skills and academic attainment, as well as academic achievements and absence rates. Present studies show that to ensure classroom IAQ conducive to learning, CO2 levels (indicating the adequacy of ventilation) should be kept below 900 ppm at all times. It should be ensured that windows can be opened when needed, to improve classroom IAQ, and CO2 sensors should be installed to indicate when windows must be open (or any other measure to improve IAQ must be executed) if the CO2 concentration is too high and when they should be closed to conserve energy
Economic Consequences
No full textIndoor air quality (IAQ) affects the quality of life by increasing the risks for health problems and reduced work performance. Consequently, different societal costs are incurred. By reducing pollutants elevating exposures indoors, and improving IAQ, these costs can be reduced or avoided. This chapter attempts to summarize the evidence and the methods for estimating the costs and economic consequences of poor IAQ affecting work performance. The value of lost work is discussed considering discomfort and health, absence from work (absenteeism), or working with limitations due to illness (presenteeism). The impact of air quality and other environmental factors on work performed at home is also presented as a hypothesis, but this evidence is limited
Metrics and Methods (Performance Indicators, Methods, and Measurement)
No full textThis chapter sets out a rationale and some detailed recommendations for selecting the most efficient metrics and methods for applied research on how any factor that determines Indoor Environmental Quality (IEQ) – such as Indoor Air Quality (IAQ) – affects building occupants, with the specific purpose of obtaining a scientific basis for the economic and engineering decisions that must be made when constructing and operating buildings. These are decisions that affect a building’s first cost, operating cost, energy-efficiency, environmental impact, and sustainability. The expense of meeting the goals in each of these areas must be justified in terms of how IEQ will affect the occupants of the building in terms of their health, comfort, and performance. There may be costs and benefits in each of these areas, and the IEQ effects on them must be quantified if they are to be used in cost-benefit analyses to justify the above expenses. The metrics and measures and the research strategy discussed in this chapter can be used for this applied purpose, to assess the effects of any environmental factor in the indoor environment, including those determining thermal conditions, air quality, acoustic conditions, and lighting
Measurements of Perceived Indoor Air Quality
No full textChemical analysis of the composition of indoor air characterizes exposures, but sometimes this analysis may be insufficient to describe the effects of these exposures on building occupants, especially to characterize sensory effects caused by exposures to pollutants in buildings. The present chapter presents the methods used to characterize these effects. The methods using olfactometers and gas chromatography- olfactometry-mass spectroscopy (GC-O-MS) are described together with the methods using sensory panels and subjective evaluations. The latter provides direct information on how indoor air quality is perceived by building occupants, and includes assessments of acceptability of air quality and the perceived odor intensity; the assessments of acceptability can be used to determine the percentage of people dissatisfied with air quality. The limitations of methods are described together with the factors influencing the measurements using human subjects, including physical factors such as temperature and relative humidity, psychological factors such as adaptation, and procedural factors such as the number of inhalations before the assessment is completed. Possible applications of the results of measurements are shown, including characterization of emissions from building products and determination of ventilation requirements to reach a specific level of air quality characterized by the percentage of dissatisfied occupants. It is concluded that the methods presented should be considered supplementary to the chemical measurements as none of both methods can provide complete characterization of indoor air quality. When used together, they provide a more comprehensive characterization of indoor air and its quality. It is subsequently recommended that sensory evaluations of air quality and olfactometry methods (also using GC-O-MS) become part of protocols used for characterizing indoor air quality because they can capture the effects and potential consequences that other methods for measuring indoor air quality are not fully capable of measuring
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Occupant Emissions and Chemistry
No full textHumans are a major source of indoor chemicals. Breath and sk Occupant-Related Chemical Transformations in emissions meaningfully contribute to the chemical composition of indoor air. Volatile organic compounds emitted by humans originate from endogenous sources (metabolic processes), and from exogenous sources (environmental exposure, diet, and personal care products). They can result from microbial activity and can lead to odor nuisance and decreased perceived air quality. The emitted compounds can undergo chemical transformations, such as ozone-initiated reactions, which produce a range of new compounds. The reactions of ozone with squalene and other constituents of skin oils have been shown to significantly alter the composition of indoor air and alter its OH reactivity. Dermal emissions may impact perceived air quality more than emissions via breath. The understanding of the effects of various environmental and personal factors (e.g., temperature, humidity, personal hygiene, diet, clothing, personal care products, age, sex, emotional state) on human emissions, their chemical transformations, and their consequences for indoor air quality, comfort, and health is limited. This chapter presents an overview of occupant emissions and the indoor air chemistry associated with them. Personal and environmental factors that may influence human emissions are discussed. Emerging research on the potential impacts of occupant emissions on perceived indoor air quality and human health is presented, and key research questions to advance our understanding of occupant-related indoor air chemistry are highlighted
Postulated Pathways Between Environmental Exposures and Cognitive Performance
No full textPathways exist between environmental exposure and cognitive performance. These include both sensory and nonsensory stimuli and moderation bodily condition, natural dispositions, and nurtured through experience, societal norms, and acclimation. Physiological and neurological mechanisms reflect natural homeostasis to stimuli. Physiological, psychological, and neurological responses are interrelated. Together, they impact the cognitive performances across the spectrum of indicators such as attention, memory, language processing, reasoning, computation, and decision-making
Indoor Air Quality in Commercial Air Transportation
No full textThis chapter deals with the air quality in means of air transportation. Since air travel in large passenger aircraft represents the vast majority of travel, the air quality in commercial aircraft cabins is vitally important to the public. At typical cruising altitudes between 31,000 and 41,000 ft (about 9,500 and 12,500 m), ambient conditions of very low temperature and pressure, elevated ozone concentrations, and dry air constitute a hostile environment to human beings. To create a life-supporting atmosphere inside the aircraft, environmental control systems provide appropriate regulation of pressure, temperature, and ventilation in the cabin. As aircraft cabins increasingly become part of the normal habitat for humans, passenger and crew expectations for the cabin environment are rising, leading to additional requirements for environmental control systems. Air pollution sources in aircraft cabins can be attributed to passengers and their personal hygiene, activities in the cabin, carry-on luggage, cabin equipment and materials, outside air contaminants, and very rarely, to abnormal conditions or pollution of system components like compressors, ducting, or fans in the air supply path. Many volatile organic compounds (VOCs) found in aircraft cabins do not differ from compounds found in residential buildings and offices, and concentrations are in the same range or even lower. Some semivolatile organic compounds (SVOCs) from, e.g., flame-retardants or operational fluids are more specific for the aircraft environment but only occur in trace concentrations. Environmental ozone can be reliably reduced in high-temperature sections of the air supply system and by employing converters. Average carbon dioxide concentrations are higher than in other environments but are kept well below regulatory limits for aircraft cabins
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