The IVAIRE project – a randomized controlled study of the impact of ventilation on indoor air quality and the respiratory symptoms of asthmatic children in single family homes

A randomized controlled trial was carried out to measure the impact of an intervention on ventilation, indoor air contaminants, and asthma symptoms of children. Eighty‐three asthmatic children living in low‐ventilated homes were followed over 2 years. Several environmental parameters were measured during the summer, fall, and winter. The children were randomized after Year 1 (43 Intervention; 40 Control). The intervention included the installation of either a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). During the fall and winter seasons, there was a significant increase in the mean ventilation rate in the homes of the intervention group. A statistically significant reduction in mean formaldehyde, airborne mold spores, toluene, styrene, limonene, and α‐pinene concentrations was observed in the intervention group. There was no significant group difference in change in the number of days with symptoms per 14 days. However, there was a significant decrease in the proportion of children who experienced any wheezing (≥1 episode) and those with ≥4 episodes in the 12‐month period in the intervention group. This study indicates that improved ventilation reduces air contaminants and may prevent wheezing. Due to lack of power, a bigger study is needed.     

A review of ventilation and the quality of ventilation air

Ventilation is pivotal in terms of securing optimum indoor air quality. In addition, it also has a major impact on energy use in buildings. It is important, therefore, that the role and impact of ventilation is fully understood and that ventilation is employed efficiently. The purpose of this paper is to review these aspects with particular reference to recent research and developments. Key aspects are concerned with identifying the role of ventilation and reviewing this role in the context of the other measures that must be taken to secure a healthy indoor environment. References are particularly made to the development of standards and recent related research. Although good progress is being made, areas that still need to be addressed include maintaining good outdoor air quality and preventing contaminated outdoor air from entering buildings. The outcome of recent research must also be disseminated in practical ways to policy makers, building occupiers and practitioners. Good indoor climate can be achieved, not so much by introducing expensive concepts, but by developing a rationale approach to identifying needs and applying the necessary tools to deal with each need.     

Day care center characteristics and children's respiratory health

Day care centers provide an important exposure arena with potential harmful health effects for children. This study has linked health effect data from a survey among 942 3-5-year-old Oslo children with information on day care center characteristics collected during inspection of the 175 day care centers these children attended. The aim of the study was to estimate associations between dampness problems and other building characteristics and several respiratory health outcomes. Dampness problems (sign of molds, water leakage, damage to floor/wall) were observed in 51% of the day care centers. In multiple logistic regression analyses none of the studied symptoms and diseases (nightly cough, blocked or runny nose without common cold, wheeze, heavy breathing or chest tightness, the common cold, tonsillitis/pharyngitis, otitis media, bronchitis, pneumonia, asthma, and allergic rhinitis) were systematically associated with dampness problems or type of ventilation in day care centers. None of the studied indicators of day care center exposures were found to have a clear effect on day care children's respiratory health. Even so this study does not rule out negative health effects of day care center exposures. The study demonstrates that population-based studies of these relations are demanding with regard to assessment of exposure and health outcomes. PRACTICAL IMPLICATIONS: Simple and easy-to-register indicators of exposures like dampness problems and type of ventilation assessed in 175 day care centers were not related to respiratory health among 3-5-year-old Norwegian children attending the day care centers. The study does not rule out negative health effects of day care center exposures, but demonstrates methodological challenges needed to be addressed in studies of health effects of the day care environment.     

Effect of mechanically induced ventilation on the indoor air quality of building envelopes

Experiments were conducted to study the effect of mechanically induced fresh-air ventilation on the indoor air quality (IAQ) of the Tuskegee Healthy House (THH), selecting the outdoor weather conditions almost identical during the “fan OFF” and “fan ON” periods. Measurements of outdoor and indoor temperature and relative humidity (RH), in addition to the indoor dust particle concentration levels and interior wall moisture content, were systematically carried out during the summer month of August 2008. Results show that the effect of mechanically induced ventilation (“fan ON” period) is to raise the indoor RH, interior wall moisture content, and indoor dust particle concentration values significantly above those measured during the “fan OFF” period. The indoor temperature increases only slightly during the “fan ON” period.     

Improving energy performance of school buildings while ensuring indoor air quality ventilation

Energy conscious design of school buildings, as well as deemed-to-satisfy provisions in a Performance Based Energy Code, should address the problem known as the energy efficiency—thermal comfort—indoor air quality dilemma (EE-TC-IAQ Dilemma). In warm and moderate climates, the large internal heat sources usually found in school buildings prevent achieving thermal comfort without active cooling in summer, but are not sufficient to eliminate the need for heating in winter. Commonly used air-conditioners do not improve air quality, while natural ventilation induces uncontrolled energy losses. In this study, a step by step process was used for the development of deemed-to-satisfy design solutions, which cope with the EE-TC-IAQ Dilemma, for a performance based code. A distinction is made between improving building design variables and improving ventilation schemes. Results indicate that implementation of improved ventilation schemes in an otherwise well designed energy-conscious building result in savings of 28–30% and 17–18% for northern and southern classroom orientations, respectively.     

The impacts of ventilation strategies and facade on indoor thermal environment for naturally ventilated residential buildings in Singapore

The impacts of various ventilation strategies and facade designs on indoor thermal environment for naturally ventilated residential buildings in Singapore are investigated in this study based on thermal comfort index. Four ventilation strategies, nighttime-only ventilation, daytime-only ventilation, full-day ventilation and no ventilation were evaluated for hot-humid climate according to the number of thermal discomfort hours in the whole typical year on the basis of a series of TAS simulations. Parametric studies of facade designs on orientations, window to wall ratios and shading devices were performed for two typical weeks by coupled simulations between building simulation ESP-r and CFD (FLUENT). The results indicate that full-day ventilation for indoor thermal comfort is better than the other three ventilation strategies. With various facade design studies, it was found that north- and south-facing facades can provide much comfortable indoor environment than east- and west-facing facades in Singapore. It is recommended that optimum window to wall ratio 0.24 can improve indoor thermal comfort for full-day ventilation and 600 mm horizontal shading devices are needed for each orientation in order to improve thermal comfort in further.     

Evaluation of the indoor air quality minimum ventilation rate procedure for use in California retail buildings

This research assesses benefits of adding to California Title‐24 ventilation rate (VR) standards a performance‐based option, similar to the American Society of Heating, Refrigerating, and Air Conditioning Engineers ‘Indoor Air Quality Procedure’ (IAQP) for retail spaces. Ventilation rates and concentrations of contaminants of concern (CoC) were measured in 13 stores. Mass balance models were used to estimate ‘IAQP‐based’ VRs that would maintain concentrations of all CoCs below health‐ or odor‐based reference concentration limits. An intervention study in a ‘big box’ store assessed how the current VR, the Title 24‐prescribed VR, and the IAQP‐based VR (0.24, 0.69, and 1.51 air changes per hour) influenced measured IAQ and perceived of IAQ. Neither current VRs nor Title 24‐prescribed VRs would maintain all CoCs below reference limits in 12 of 13 stores. In the big box store, the IAQP‐based VR kept all CoCs below limits. More than 80% of subjects reported acceptable air quality at all three VRs. In 11 of 13 buildings, saving energy through lower VRs while maintaining acceptable IAQ would require source reduction or gas‐phase air cleaning for CoCs. In only one of the 13 retail stores surveyed, application of the IAQP would have allowed reduced VRs without additional contaminant‐reduction strategies.     

Indoor air pollution from biomass combustion and respiratory symptoms of women and children in a Zimbabwean village

Rural areas of developing countries are particularly reliant on biomass for cooking and heating. Women and children in these areas are often exposed to high levels of pollutants from biomass combustion that is associated with a range of respiratory symptoms. Domestic exposure to carbon monoxide (CO) and respirable particles (RSPs) in association with respiratory symptoms among women and children in Zimbabwe was investigated in 48 households. Health status and household characteristics were also recorded. In this study, indoor levels of CO and RSPs exceeded World Health Organization (WHO) air quality guidelines in over 95% of kitchens. The level of indoor air pollutants was associated with the area of kitchen windows and the length of cooking time combined with the level of fire combustion. Prevalence of respiratory symptoms was 94% for women and 77% for children. In addition, women reporting respiratory symptoms were exposed to higher levels of RSPs when compared with those reporting no respiratory symptoms. The study results indicated that levels of indoor air pollutants in rural Zimbabwe may contribute to respiratory symptoms in both women and children. PRACTICAL IMPLICATIONS: Levels of respirable particles and carbon monoxide in kitchens in rural Zimbabwe are unacceptably high and measures to reduce levels should be undertaken. Based on the study findings, recommendations for increasing the area of kitchen windows may be considered as a practical method of reducing indoor air pollutants in rural Zimbabwe.     

Parental worry about indoor air quality and student symptom reporting in primary schools with or without indoor air quality problems

Poor indoor air quality (IAQ) in schools is related to increased symptom reporting in students. We investigated whether parental worry about school IAQ influences this association. Data came from survey collected from five Finnish primary schools with observed IAQ problems and five control schools. Parents (n = 1868) of primary school students reported worry about IAQ in schools and symptoms of their children. Associations between observed IAQ problems, worry, and five symptom scores (ie, respiratory, lower respiratory, eye, skin, and general symptoms) were analyzed using multivariate logistic regression and mediation analysis. Parents were on average more worried in schools with observed IAQ problems. Observed IAQ problems were strongly associated with increased worry and all symptoms under study (unadjusted ORs ranged between 1.48 [95% CI 1.48‐2.16] and 2.70 [95% CI 1.52‐5.17]). Parental worry was associated with all symptoms (unadjusted ORs ranged between 2.49 [95% CI 1.75‐3.60] and 4.92 [95% CI 2.77‐9.40]). Mediation analyses suggested that parental worry might partially explain the association between observed IAQ problems and symptom reporting (proportion mediated ranged between 67% and 84% for the different symptoms). However, prospective studies are needed to assess causal relationships between observed IAQ problems, worry, and symptom reporting in schools.     

Indoor air quality and the law in Singapore

With the greater use of air-conditioned offices in Singapore, achieving good indoor air quality has become an important issue. The laws that impose duties upon designers and contractors with respect to the design and construction of air-conditioning and mechanical ventilation (ACMV) systems are set out in the Building Control Regulations and the Singapore Standard Code of Practice for Mechanical Ventilation and Air-conditioning in Buildings (hereinafter "SS CP 13:1980"). ACMV maintenance is governed by the Environmental Public Health Act, the Building and Common Property (Maintenance and Management) Act, and the Land Titles (Strata) Act, as well as by lease or tenancy agreements. Designers, contractors, developers, building owners and management corporations may also be liable to the workers, occupants and other premises users for indoor air quality (IAQ)-related injuries under the general principles of contract and tort. Recently, the Guidelines for Good Indoor Air Quality in Office Premises was issued by the Ministry of Environment to complement SS CP 13:1980 toward improving the indoor air quality of air-conditioned office premises. Although the Guidelines have no statutory effect, they may be adopted as contractual requirements in construction, lease and maintenance contracts. They may also be used to determine the relevant standard of duty of care required to discharge tortious liability. This paper looks at the existing laws and rules affecting the design, construction and maintenance of air-conditioned offices in light of Part III of the Ministry's Guidelines.     

Comparison of strategies to improve indoor air quality at the pre-occupancy stage in new apartment buildings

Indoor air quality of new apartment buildings, which is known to cause Sick Housing Syndrome, has become a major concern among apartment residents as well as construction companies in Korea. Recently, the Indoor Air Quality Management Act, a regulation that limits concentration levels of formaldehyde and five volatile organic compounds in new apartment buildings, has been implemented. In this study, the effects of ventilation and decomposing agents were investigated and compared, which could be used at the pre-occupancy stage as solutions to high VOCs concentration levels in new apartment buildings. Six housing units were investigated under different conditions to assess the extent of the improvement in indoor air quality. The results demonstrate that ventilation is an effective way to control indoor air pollution caused by VOCs emissions, and the effect of decomposing agents on improving indoor air quality depends on the types of VOCs.     

Effectiveness of heating, ventilation and air conditioning system with HEPA filter unit on indoor air quality and asthmatic children's health

Poor indoor air quality has been linked to the exacerbation of asthma symptoms in children. Because people spend most of their time indoors, improving indoor air quality may provide some relief to asthma sufferers. A study was conducted to assess whether operating an air cleaning/ventilating unit (HEPAiRx^®) in a child's bedroom can improve his/her respiratory health. Thirty children diagnosed with asthma were randomly split into two groups. For the first six weeks, group A had the air cleaning/ventilating unit (HEPAiRx^®) running in the bedrooms of the participants and group B did not; for the second six weeks, both groups had the cleaners running in the bedrooms; and, for the final six weeks, group A turned the cleaners off and group B kept theirs running. Indoor air quality parameters, including temperature, relative humidity, particulate matter (PM 0.5–10 μm), carbon monoxide, carbon dioxide and total volatile organic compound (TVOC) concentrations, were monitored in each bedroom using an AirAdvice indoor air quality multi-meter. As a measure of pulmonary inflammation, exhaled breath condensate (EBC) was collected every sixth day and analyzed for nitrate and pH. Peak expiratory flow (PEF) was also measured. PM and TVOC concentrations decreased with operation of the HEPAiRx an average of 72% and 59%, respectively. The EBC nitrate concentrations decreased significantly and the EBC pH and PEF values increased significantly with operation of the unit (p < 0.001 when comparing on/off sample means). These results indicate that air cleaning in combination with ventilation can effectively reduce symptoms for asthma sufferers.     

The effect of housing characteristics and occupant activities on the respiratory health of women and children in Lao PDR

The paper presents the results of a study conducted into the relationship between dwelling characteristics and occupant activities with the respiratory health of resident women and children in Lao People's Democratic Republic (PDR). Lao is one of the least developed countries in south-east Asia with poor life expectancies and mortality rates. The study, commissioned by the World Health Organisation, included questionnaires delivered to residents of 356 dwellings in nine Districts in Lao PDR over a five month period (December 2005-April 2006), with the aim of identifying the association between respiratory health and indoor air pollution, in particular exposures related to indoor biomass burning. Adjusted odds ratios were calculated for each health outcome separately using binary logistic regression. After adjusting for age, a wide range of symptoms of respiratory illness in women and children aged 1-4 years were positively associated with a range of indoor exposures related to indoor cooking, including exposure to a fire and location of the cooking place. Among women, “dust always inside the house” and smoking were also identified as strong risk factors for respiratory illness. Other strong risk factors for children, after adjusting for age and gender, included dust and drying clothes inside. This analysis confirms the role of indoor air pollution in the burden of disease among women and children in Lao PDR.     

Analysis of thermal comfort and indoor air quality in a mechanically ventilated theatre

Theatres are the most complex of all auditorium structures environmentally. They usually have high heat loads, which are of a transient nature as audiences come and go, and from lighting which changes from scene to scene, and they generally have full or nearly full occupancy. Theatres also need to perform well acoustically, both for the spoken word and for music, and as sound amplification is less used than in other auditoria, background noise control is critically important. All these factors place constraints on the ventilation design, and if this is poor, it can lead to the deterioration of indoor air quality and thermal comfort. To analyse the level of indoor air quality and thermal comfort in a typical medium-sized mechanically ventilated theatre, and to identify where improvements could typically be made, a comprehensive post-occupancy evaluation study was carried out on a theatre in Belgrade. The evaluation, based on the results of monitoring (temperature, relative humidity, CO₂, air speed and heat flux) and modelling (CFD), as well as the assessment of comfort and health as perceived by occupants, has shown that for most of the monitored period the environmental parameters were within the standard limits of thermal comfort and IAQ. However, two important issues were identified, which should be borne in mind by theatre designers in the future. First, the calculated ventilation rates showed that the theatre was over-ventilated, which will have serious consequences for its energy consumption, and secondly, the displacement ventilation arrangement employed led to higher than expected complaints of cold discomfort, probably due to cold draughts around the occupants’ feet.     

Natural ventilation of indoor spaces while minimizing heat losses: Theoretical and experimental investigation

Limiting heat losses during ventilation of indoor building spaces has become a basic aim for architects, particularly since the oil crisis of 1970. Much experience has been gained in terms of ventilation of indoor spaces. Nevertheless, due to the complex applications, attempts to create a theoretical base for solving the problems related to the issue are limited, especially determining the minimum ventilation period required within a designated space. In this paper we have approached this matter, both theoretically and experimentally. The conclusion we reached was that controlled ventilation of spaces through vent holes that successively open and close at regular time intervals can limit the excessive circulation of air masses, which in turn limits heat losses.     

Characterization of indoor air quality using multiple measurements of nitrogen dioxide

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Daily indoor and outdoor NO2 concentrations were measured for 30 consecutive days in 28 houses in Brisbane, Australia, and for 21 consecutive days in 37 houses in Seoul, Korea. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and NO2 source strength were estimated. Geometric means of ventilation rate were 1.44 air change per hour (ACH) in Brisbane, assuming a residential NO2 deposition constant of 1.05/h, and 1.36 ACH in Seoul, with the measured residential NO2 deposition constant of 0.94/h. Source strengths of NO2 were 15.8 +/- 18.2 and 44.7 +/- 38.1 microg/m3/h in Brisbane and Seoul, respectively. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.     

Valuing the health benefits of improving indoor air quality in residences

Unlike commercial premises, the indoor air quality of residences is more dynamic, uncontrolled, and prone to human behavioral changes. In consequence, measuring the health benefit gains derived from improving indoor air quality in residences is more complicated. To overcome this, a human thermal comfort model was first integrated with indoor microenvironment models, and subsequently linked with appropriate concentration-response and economic data for estimating the economic benefit gains derived from improving indoor air quality in residences for an adult and an elderly person. In this study, the development of the model is illustrated by using a typical residential apartment locating at the worst air quality neighborhood in Hong Kong and the daily weather profiles between 2002 and 2006. Three types of personal intervention measures were examined in the study: (i) using air cleaner in residence, (ii) changing time spent in residence, and (iii) relocating to a better air quality neighborhood. Our results revealed that employing air cleaners with windows closed in residence throughout the entire year was the most beneficial measure as it could provide the greatest annual health benefit gains. It would give a maximum of HK$2072 in 5-year cumulative benefit gain for an adult and HK$1700 for an elderly person. Employing air cleaners with windows closed in only cool season (October through March) could give the highest marginal return per dollar spent. The benefit gains would become smaller when windows were opened to a greater extent. By contrast, relocating to a better air quality neighborhood and changing the time spent in residence did not appeal to be beneficial intervention measures.     

The effect of environmental and structural factors on indoor air quality of apartments in Korea

The indoor air quality (IAQ) was measured in newly built Korean apartments before and after occupancy in a survey of 158 residences in 24-apartment complexes nationwide. Factors that might affect pollutant concentration, such as temperature, humidity, housing size, and duration of occupancy, were analyzed in relation to the measured concentrations. Average pollutant levels were consistent with the Ministry of the Environment's recommended standards; however, pollutant levels in some apartments exceeded the current standards. We found that the concentrations of formaldehyde and toluene often exceeded the more stringent guidelines that will soon be enacted. Our results suggest that stronger countermeasures are therefore required to control these two chemicals. The results show that the pollution concentration was generally proportional to temperature and humidity, but that, in some cases, the concentration measurements were inversely proportional to these two factors, and in a few others the relationship between these factors was not clear. Indoor air pollution readings were highest in the 30-pyeong apartments, followed by 10-, and 20-pyeong residences. The pollutant concentrations decreased to about half of their initial levels after one year of occupancy, but the concentration of formaldehyde in indoor air persisted for a longer period. The duration of the apartment's occupancy affected indoor air pollutant concentrations more so than other factors such as temperature, humidity, and apartment size.