Indoor Air Quality

[Excerpt] “Indoor air quality or IAQ” is what we experience as the temperature, humidity, ventilation, and chemical or biological contaminants of the air inside non-industrial buildings, such as schools, offices, hotels, or banks – environments typically considered pristine when compared with industrial settings. In today’s world, we spend about 90% of our day indoors and the pollution indoors can be 2 to 5 times – and occasionally more than 100 times -- higher than outdoor levels. After all, we humans exhale (and otherwise produce) the endproducts of metabolism. We shed hair and dander. We have in our buildings all kinds of textiles, equipment, paper, cleaning products, and maintenance activities – so the air can be very different from “fresh outside air.” We notice this difference – sometimes simply as odors and sometimes as symptoms such as: • irritation of eyes, nose, or throat • dry mucous membranes and skin • erythema – reddening or flushing of the face or skin • mental fatigue, headache, sleepiness • airway infections, cough • hoarseness, wheezing • nausea, dizziness • hypersensitivity reactions. Studies of buildings have indicated that poor IAQ can cause health problems, affect occupants’ productivity and reduce learning, as well as have liability issues and cause poor public relations – a building gets a bad reputation which affects leasing and purchasing

A comparison of different ventilation strategies for dwellings in terms of airflow rates and airflow paths

The context of ventilation in Belgian dwellings has changed since the publication of the Belgian standard NBN D 50-001:1991. Due to the higher energy performance of these dwellings, ventilation plays nowadays a more essential role in maintaining a good indoor air quality. Therefore, new rules for improved ventilation strategies are needed to accomplish high energy-efficient ventilation while providing a good indoor air quality. A first step is to compare different ventilation strategies, including strategies that don’t comply with the current standard, in terms of airflow rates and airflow paths. This comparison also includes the influence of demand controlled ventilation. This paper covers a simulation study using multi-zone airflow and contaminant transport calculation software (CONTAM) which compares the performances of the different ventilation strategies in terms of indoor air quality and average airflow rates. The evaluation of the indoor air quality is based on the exposure of the occupants to CO2 and VOC and on the relative humidity in the rooms. The different ventilation strategies can achieve a comparable indoor air quality, including the strategies not conform to the Belgian standard. However, some strategies require up to twice the airflow rate than others

Optimization on fresh outdoor air ratio of air conditioning system with stratum ventilation for both targeted indoor air quality and maximal energy saving

Stratum ventilation can energy efficiently provide good inhaled indoor air quality with a proper operation (e.g., fresh outdoor air ratio). However, the non-uniform CO2 distribution in a stratum-ventilated room challenges the provision of targeted indoor air quality. This study proposes an optimization on the fresh outdoor air ratio of stratum ventilation for both the targeted indoor air quality and maximal energy saving. A model of CO2 concentration in the breathing zone is developed by coupling CO2 removal efficiency in the breathing zone and mass conservation laws. With the developed model, the ventilation parameters corresponding to different fresh outdoor air ratios are quantified to achieve the targeted indoor air quality (i.e., targeted CO2 concentration in the breathing zone). Using the fresh outdoor air ratios and corresponding ventilation parameters as inputs, energy performance evaluations of the air conditioning system are conducted by building energy simulations. The fresh outdoor air ratio with the minimal energy consumption is determined as the optimal one. Experiments show that the mean absolute error of the developed model of CO2 concentration in the breathing zone is 1.9%. The effectiveness of the proposed optimization is demonstrated using TRNSYS that the energy consumption of the air conditioning system with stratum ventilation is reduced by 6.4% while achieving the targeted indoor air quality. The proposed optimization is also promising for other ventilation modes for targeted indoor air quality and improved energy efficiency

The state of indoor air quality in Pakistan—a review

Background and purpose: In Pakistan, almost 70% of the population lives in rural areas. Ninety-four percent of households in rural areas and 58% in urban areas depend on biomass fuels (wood, dung, and agricultural waste). These solid fuels have poor combustion efficiency. Due to incomplete combustion of the biomass fuels, the resulting smoke contains a range of health-deteriorating substances that, at varying concentrations, can pose a serious threat to human health. Indoor air pollution accounts for 28,000 deaths a year and 40 million cases of acute respiratory illness. It places a significant economic burden on Pakistan with an annual cost of 1% of GDP. Despite the mounting evidence of an association between indoor air pollution and ill health, policy makers have paid little attention to it. This review analyzes the existing information on levels of indoor air pollution in Pakistan and suggests suitable intervention methods. Methods: This review is focused on studies of indoor air pollution, due to biomass fuels, in Pakistan published in both scientific journals and by the Government and international organizations. In addition, the importance of environmental tobacco smoke as an indoor pollutant is highlighted. Results: Unlike many other developing countries, there are no long-term studies on the levels of indoor air pollution. The limited studies that have been undertaken indicate that indoor air pollution should be a public health concern. High levels of particulate matter and carbon monoxide have been reported, and generally, women and children are subject to the maximum exposure. There have been a few interventions, with improved stoves, in some areas since 1990. However, the effectiveness of these interventions has not been fully evaluated. Conclusion: Indoor air pollution has a significant impact on the health of the population in Pakistan. The use of biomass fuel as an energy source is the biggest contributor to poor indoor air quality followed by smoking. In order to arrest the increasing levels of indoor pollution, there is a dire need to recognize it as a major health hazard and formulate a national policy to combat it. An integrated effort, with involvement of all stakeholders, could yield promising results. A countrywide public awareness campaign, on the association of indoor air pollution with ill health, followed by practical intervention would be an appropriate approach. Due to the current socioeconomic conditions in the country, development and adoption of improved cooking stoves for the population at large would be the most suitable choice. However, the potential of biogas as a fuel should be explored further, and modern fuels (natural gas and LPG) need to be accessible and economical. Smoking in closed public spaces should be banned, and knowledge of the effect of smoking on indoor air quality needs to be quantified. © 2010 Springer-Verlag

Relative and contextual contribution of different sources to the composition and abundance of indoor air bacteria in residences.

BackgroundThe study of the microbial communities in the built environment is of critical importance as humans spend the majority of their time indoors. While the microorganisms in living spaces, especially those in the air, can impact health and well-being, little is known of their identity and the processes that determine their assembly. We investigated the source-sink relationships of airborne bacteria in 29 homes in the San Francisco Bay Area. Samples taken in the sites expected to be source habitats for indoor air microbes were analyzed by 16S rRNA-based pyrosequencing and quantitative PCR. The community composition was related to the characteristics of the household collected at the time of sampling, including the number of residents and pets, activity levels, frequency of cooking and vacuum cleaning, extent of natural ventilation, and abundance and type of vegetation surrounding the building.ResultsIndoor air harbored a diverse bacterial community dominated by Diaphorobacter sp., Propionibacterium sp., Sphingomonas sp., and Alicyclobacillus sp. Source-sink analysis suggested that outdoor air was the primary source of indoor air microbes in most homes. Bacterial phylogenetic diversity and relative abundance in indoor air did not differ statistically from that in outdoor air. Moreover, the abundance of bacteria in outdoor air was positively correlated with that in indoor air, as would be expected if outdoor air was the main contributor to the bacterial community in indoor bioaerosols. The number of residents, presence of pets, and local tap water also influenced the diversity and size of indoor air microbes. The bacterial load in air increased with the number of residents, activity, and frequency of natural ventilation, and the proportion of bacteria putatively derived from skin increased with the number of residents. Vacuum cleaning increased the signature of pet- and floor-derived bacteria in indoor air, while the frequency of natural ventilation decreased the relative abundance of tap water-derived microorganisms in air.ConclusionsIndoor air in residences harbors a diverse bacterial community originating from both outdoor and indoor sources and is strongly influenced by household characteristics

A comparative study of selected sorbents for sampling of aromatic VOCs from indoor air

Indoor air canbecome pollutedwith VOCs, and understanding the factors which affect adsorption of VOCs from indoor air is important for: (i) the accurate measurement of VOCs, and (ii) to apply mitigation strategies when high analyte concentrations are measured. In this study four VOCs (toluene, ethylbenzene, cumene and dichlorobenzene) were generated as a constant and controlled polluted air stream of VOCs from a dynamic atmospheric chamber. The effects of relative humidity, and sampling flow rate, on adsorption onto Tenax TA and the relatively new silica adsorbents SBA-15 or MCM-41 were studied

Dispersal in microbes: fungi in indoor air are dominated by outdoor air and show dispersal limitation at short distances.

The indoor microbiome is a complex system that is thought to depend on dispersal from the outdoor biome and the occupants' microbiome combined with selective pressures imposed by the occupants' behaviors and the building itself. We set out to determine the pattern of fungal diversity and composition in indoor air on a local scale and to identify processes behind that pattern. We surveyed airborne fungal assemblages within 1-month time periods at two seasons, with high replication, indoors and outdoors, within and across standardized residences at a university housing facility. Fungal assemblages indoors were diverse and strongly determined by dispersal from outdoors, and no fungal taxa were found as indicators of indoor air. There was a seasonal effect on the fungi found in both indoor and outdoor air, and quantitatively more fungal biomass was detected outdoors than indoors. A strong signal of isolation by distance existed in both outdoor and indoor airborne fungal assemblages, despite the small geographic scale in which this study was undertaken (<500 m). Moreover, room and occupant behavior had no detectable effect on the fungi found in indoor air. These results show that at the local level, outdoor air fungi dominate the patterning of indoor air. More broadly, they provide additional support for the growing evidence that dispersal limitation, even on small geographic scales, is a key process in structuring the often-observed distance-decay biogeographic pattern in microbial communities

Bedroom indoor air comfort : a critical analysis

The criteria that are currently used for the assessment of Indoor Air Quality in a residential context were developed in the ‘80s and relate to comfort during occupancy. More than half the time at home however, is spent in the bedroom. There is no strong indication that the criteria that are traditionally used to assess Indoor Air Quality also relate to the level of comfort while asleep. Moreover, analysis of the results of a performance assessment of frequently used residential ventilation systems based on these traditional criteria, shows that they are dominated by the pollution level in the bedrooms