Cost assessment of ventilation and averted dose due to radon in dwellings

The inhalation dose due to radon and its progenies could be averted by ventilation in dwellings; however, on the other hand the increased ventilation augments the heating cost. Therefore a cost-benefit analysis could contribute to optimise the ventilation rate. In our current work we applied our former defined parameters of the optimising procedure to assess the optimised ventilation and radon concentration in dwellings with average parameters. To assess the inhalation dose rates the time-dependent concentrations of all the progenies were calculated in case of periodic and continuous ventilation as well, at three different radon entry rates (5, 10, 20kBqh(-1)). The optimal ventilation rates in case of continuous ventilation are 0.22, 0.40 and 0.66h(-1), respectively. By these conditions the optimal radon concentration takes 160-210Bqm(-3). According to the more detailed analysis the periodic ventilation gives, in general, a better solution than the continuous one. The Monte Carlo simulations provided a large uncertainty; therefore, before the practical application of the results the uncertainty should be decreased taken into account the local conditions.     

Deposition rates of unattached and attached radon progeny in room with turbulent airflow and ventilation

In this paper deposition rate coefficients for unattached and attached radon progeny were estimated according to a particle deposition model for turbulent indoor airflow described by Zhao and Wu [2006. Modeling particle deposition from fully developed turbulent flow in ventilation duct. Atmos. Environ. 40, 457–466]. The parameter which characterizes turbulent indoor airflow in this model is friction velocity, u*. Indoor ventilation changes indoor airflow and friction velocity and influences deposition rate coefficients. Correlation between deposition and ventilation rate coefficients in the room was determined. It was shown that deposition rate coefficient increases with ventilation rate coefficient and that these parameters of the Jacobi room model cannot be assumed to be independent. The values of deposition rate coefficients were presented as functions of friction velocity and ventilation rate coefficient. If ventilation rate coefficient varies from 0.1 up to 1 h⁻¹, deposition rate coefficients for unattached and attached fractions were estimated to be in the range 3–110 h⁻¹ and 0.015–0.35 h⁻¹, respectively.     

Low-infiltration housing in Rochester, New York: A study of air-exchange rates and indoor air quality

A sample of 58 occupied homes in Rochester, NY, most of which incorporated special builder-designed weatherization components, were studied to assess (1) the effectiveness of construction techniques designed to reduce air leakage; (2) the indoor air quality and air-exchange rates in selected airtight houses, and (3) the impact on indoor air quality of mechanical ventilation systems employing air-to-air heat exchangers. The “specific leakage area” was measured in each house using the fan pressurization technique. Houses built with polyethylene vapor barriers and joint-sealing were as a group 50% tighter than a similar group of houses without such components. Mechanical ventilation systems with air-to-air heat exchangers were installed in nine relatively airtight houses, some of which had gas stoves and/or tobacco smoking occupants. Air-exchange rates and indoor concentrations of radon (Rn), formaldehyde (HCHO), nitrogen dioxide (NO₂), and humidity were measured in each house for 1-week periods with and without mechanical ventilation. More detailed measurements, including concentrations of carbon monoxide and inhalable particulates, were made in two of these houses by a mobile laboratory. In all nine houses, air-exchange rates were relatively low (0.2–0.5 ach) without mechanical ventilation, and yet indoor concentrations of Rn, HCHO, and NO₂ were below existing guidelines. Mechanical ventilation systems were effective in further reducing indoor contaminant concentrations. We conclude that when contaminant source strengths are low, acceptable indoor air quality can be compatible with low air-exchange rates.     

Methods for control of indoor air quality

This report presents results of a review of available methods for control of environmental hazards applied to indoor air pollutants. Indoor air pollution originates from transport of ambient outdoor air contaminants into occupied spaces by natural infiltration ventilation, or by mechanical ventilation using outdoor makeup air, plus contributions from indoor emission sources. When air exchange with the external ambient environment is reduced to conserve energy, contributions from indoor emission sources may dominate indoor air pollutant levels. This paper identifies alternative methods available to control indoor air pollutant exposures. The performance characteristics of ventilation systems and of air cleaning devices used in mixed modes for ventilation of occupied spaces are described. Models for predicting effectiveness of several alternative modes are reviewed, with field trial validation results cited where available. Results of previous confined-space studies are briefly reviewed as points of departure for consideration of necessary air quality, ventilation, and air cleaning. Understanding of indoor air contaminant generation and controls is aided by examination of earlier studies of indoor air quality, using modern perspectives on occupational environmental health and hygiene.     

Ventilation efficiency

Research indicates that ventilating systems can be designed for higher ventilation efficiency in the zone of occupation than systems designed for complete mixing. Expressions for ventilation efficiency are derived using a two-box theoretic model. These definitions of ventilation efficiency can be used for practical measurements, and also seem to be valid for multibox schemes. Measurements reviewed show that diagonal schemes are the most efficient. Short-circuiting schemes, with warm air supply along the ceiling and high wall exhaust, produce very low efficiencies. The mathematical model predicts high efficiencies using diffuse air supply directly to the zone of occupation, if the air is not used heating.     

The activity of radon daughters in high-rise buildings and the influence of soil emanation

Forty measurements are reported in similar rooms in two high-rise buildings. The geometrical means for the concentration of radon daughters including and excluding the basement results, respectively, were 0.90 and 1.00 mWL, which is less than the quoted mean 2.0 mWL for 65 measurements in typical houses in the same city. The frequency distribution of these measurements shows a log-normal distribution. The concentrations did not depend on the distance from ground level but may depend on the ventilation rate of the room examined. The correlation between the concentration of radon daughters in WL in rooms above the first floor in the two high-rise buildings with the inverse of their ventilation rate were 0.73 and 0.67, respectively.     

Guidelines for Nordic building regulations regarding indoor air quality

A subcommittee of the Nordic Committee for Building Codes has released guidelines for building regulations regarding indoor air quality, especially concerning ventilation. The main features of the guidelines, such as acceptable outdoor air quality for ventilation and minimum outdoor air flows for dwellings and offices, are presented and discussed. Mechanical ventilation is, in principle, required in all buildings including dwellings, due to the requirement of a minimum outdoor air change of 0.5 h⁻¹ and the normal highly airtight nature of new buildings. The guidelines are a basis for designing energy-efficient buildings while maintaining an indoor air quality which provides acceptable comfort and does not impair health.     

A new concept of carbon dioxide accelerated ammonia release from liquid manure in pig house

Indoor air quality in animal buildings is very important to the health of agricultural workers and animals. Carbon dioxide (CO2) and ammonia (NH3) are two of the most important pollutants in pig houses. Four tests were conduced in a mechanically ventilated pig house to study release behaviors of CO2 and NH3 from liquid manure using impulse, pulse and step ventilation inputs. The CO2 and NH3 concentrations were sampled in the exhaust chimney and measured with a CO2 monitor and a NOx analyzer, respectively. The ventilation rate was measured with a ventilation rate sensor in the chimney. A new phenomenon, characterized by a delayed dynamic response of NH3 release to the high ventilation inputs as compared with the response of CO2 release, was encountered. A new CO2 factor was identified as the cause of the delayed NH3 response. An original concept of Carbon-dioxide Accelerated Ammonia Release (CAAR) was developed. It explained that, at the initial stage of gas release induced by the high ventilation, the high release of CO2 gradually raised the pH in the surface manure. The increased pH accelerated the release of NH3. The higher release of NH3 had a negative feedback to the pH. The effects of CO2 and NH3 releases on the pH finally reached a dynamic equilibrium. The NH3 release under the dynamic equilibrium was greatly accelerated compared to that under initial conditions.     

Calculation of ventilation requirements in the case of intermittent pollution: Application to enclosed parking garages

The ventilation requirements for decontamination are normally determined with a static calculation method. In some cases, the pollutant emission is intermittent, for example in the car park of an office building, where all the cars enter and leave the place nearly at the same time. Generally, in such a case, the volume of the garage is large, consequently the time constant of the system has a high value. So a static approach would no longer stay accurate and a dynamic evaluation is needed. With the help of some assumptions, calculations remain rather simple and results can be plotted on nomonographs or computed on a programmable handheld calculator. The amount of energy saved may appear very large in some cases. A sizing optimization will be required but also remains easy to compute. The paper presents the method of calculation for a single ventilation level and the optimization of a two-level ventilation.     

Variations of airborne and waterborne Rn-222 in houses in Maine

Concentrations of airborne radon ranging from 0.05 to 135 pCi/L were found in houses in Maine. Tracketch cups were placed in five positions for 100 houses to determine integrated average radon concentrations over the period October 1980–May 1981. To investigate the association between elevated radon concentrations in well water and the indoor airborne radon concentrations, the radon in the water supplies of these houses was measured by liquid scintillation. Monitors of airborne radon, recording in intervals of 10 min for periods of 5–7 days, were used for dynamic studies in 18 houses, determining the component of airborne radon associated with major water uses, such as showers, laundry, and dishwashing, which liberate radon in bursts. House residents kept logs noting the time of major water uses. For some of the houses, ventilation rates ranging from 0.3 to 2 air changes per hour were determined by analysis of the dynamic data. The component of airborne radon associated with water sources was found to vary inversely with ventilation rate and directly with waterborne radon concentration, with 0.8 ± 0.2 pCi Rn/L air per nCi Rn/L water at a ventilation rate of 1.0 air change per hour. The data are pertinent to a study which has revealed significant correlations between county averages, from the National Cancer Institute, or age-adjusted cancer mortality rates in Maine and average values of radon concentrations in water for the counties.     

Ventilation requirements in occupied spaces during smoking and nonsmoking occupancy

Ventilation requirements in occupied spaces have traditionally derived largely from odor control. The requirements have rested on the notion that an environment that seems subjectively acceptable to a visitor will in fact be healthful and comfortable for both visitor and occupant alike. Ventilation requirements have derived secondarily from criterion concentrations of notable contaminants (e.g., carbon dioxide). The present investigation looked again at both sensory (odor, irritation) and physical criteria of acceptability, paying particular attention to the difference between smoking and nonsmoking occupancy in a well-controlled environmental chamber. More than 200 persons (visitors) made judgments of odor intensity and acceptability under various conditions of occupancy (up to 12 nonsmoking occupants; a temperature of up to 25.5°C; up to 16 cigarettes smoked per hour). The results implied that under nonsmoking conditions and moderate humidity only about 7.5 cfm (3.8 L sec⁻¹) of fresh air per occupant sufficed to satisfy visitors, but that under smoking conditions at least 5 times as much fresh air is necessary. Our estimate of ventilation requirements for smoking were derived in part from measurements of carbon monoxide and total suspended particulate (TSP) mass concentration. Levels of TSP achieved during realistic smoking and ventilation rates exceeded levels deemed acceptable outdoors. Surfaces in the chamber played an important role in the elimination of particles, presumably via adsorption. Use of an electrostatic precipitator could keep TSP levels under control. Nevertheless, it remains to be seen whether control of TSP will eliminate the need for enormous ventilation for odor control during smoking occupancy.     

Variation of indoor radon progeny concentration and its role in dose assessment

Instantaneous measurements of equilibrium equivalent concentration of radon (EEC(Rn)) were taken over a period of 1 year in 2004 in a typical house at Amritsar city, located in the northwest part of India. A method based on absolute beta counting subsequent to grab aerosol sampling was used. During that year, EEC(Rn) varied between 1.56B qm(-3) and 22.77B qm(-3) with average value of 8.76Bb qm(-3). EEC(Rn) decreased with the transition from winter to summer and vice versa, having a negative correlation with outdoor temperature. The use of mechanical ventilation, under normal living conditions during summer, caused an extra decrease in the concentrations. The variations with temperature and mechanical ventilation are discussed. Some major issues related to the uncertainties in dose calculations caused by the lack of knowledge of equilibrium factor and ignoring the effect of life style on the radon and its progeny concentrations are discussed.     

基于无机氮磷利用特征的小球藻优化培养技术

氮磷对小球藻的生长产生重要影响,基于氮磷优化培养条件的探讨具有理论和实际意义。在静置培养、通气培养和通气加碳源（葡萄糖）培养等条件下对小球藻的生长影响和氮磷消耗进行了试验,采用分批取样补料方式对培养过程进行了优化研究。结果表明,在未调节培养液pH值条件下,藻液的pH值在7~9变化,随培养时间呈略微下降的趋势。各培养条件下,小球藻对硝酸盐的吸收速率均表现出先快后慢的特征,对磷的吸收利用表现为总磷先快速被吸收利用,然后稳定在一定范围内波动。小球藻的生长在静置培养条件下主要受培养液中硝酸盐氮含量和培养液pH值的影响,通气培养条件下主要受培养液中硝酸盐氮含量的影响,通气外加碳源培养条件下主要受培养液中可溶解性总磷含量和硝酸盐氮含量双重影响。在通气外加碳源分批取样补料的藻类优化培养中,生长中期取样补料小球藻生长速率受影响较小,单位时间生物量最高,达3 565 mg/（L·d     

The effects of ventilation on residential air pollution due to emissions from a gas-fired range

The use of indoor combustion appliances can cause an increase in the levels of many different pollutants. The work presented here shows the usefulness of a model for extrapolating environmental chamber results on pollutant emissions from combustion appliances to determine indoor pollutant concentrations in actual residences. In addition, the effects of infiltration, whole-house ventilation, and spot ventilation on pollutant levels are investigated. The results show that a range hood is the most effective means of removing pollutants emitted from a gas-fired range; removal rates varied from 60% to 87%.     

Spatial and time variations of radon-222 concentration in the atmosphere of a dead-end horizontal tunnel

The concentration of radon-222 has been monitored since 1995 in the atmosphere of a 2 m transverse dimension, 128 m long, dead-end horizontal tunnel located in the French Alps, at an altitude of 1600 m. Most of the time, the radon concentration is stable, with an average value ranging from 200 Bq m(-3) near the entrance to about 1000 Bq m(-3) in the most confined section, with an equilibrium factor between radon and its short-lived decay products varying from 0.61 to 0.78. However, radon bursts are repeatedly observed, with amplitudes reaching up to 36 x 10(3) Bq m(-3) and durations varying from one to several weeks, with similar spatial variations along the tunnel as the background concentration. These spatial variations are qualitatively interpreted in terms of natural ventilation. Comparing the radon background concentration with the measured radon exhalation flux at the wall yields an estimate of 8+/-2 x 10(-6) s(-1) (0.03+/-0.007 h(-1)) for the ventilation rate. The hypothesis that the bursts could be due to transient changes in ventilation can be ruled out. Thus, the bursts are the results of transient increased radon exhalation at the walls, that could be due to meteorological effects or possibly combined hydrological and mechanical forcing associated with the water level variations of the nearby Roselend reservoir lake. Such studies are of interest for radiation protection in poorly ventilated underground settings, and, ultimately, for a better understanding of radon exhalation associated with tectonic or volcanic processes.     

A CO2-controlled ventilation system

For buildings in which the emissions from people is the main source of pollution, the number of people is the limiting factor for air ventilation. When such buildings are not used at full capacity, the ventilation, and consequently the energy consumption, is unnecessarily high. A great deal of the energy could be saved if the ventilation system could be developed to adjust the air flow to the actual requirements. One possible system would allow the amount of CO₂ in the exhaust air to control the ventilation rate. To study if this principle is practicable and economic, a CO₂ indicator has been installed in an office building in Helsinki. The mixture of exterior air and recirculated air is adjusted so that the amount of CO₂ during working hours is kept on ca 700 ppm (μL/L). The equipment was used during winter 1981-82, and the variation of CO₂ and the exterior air flow has been registered. The proportion of CO₂ has also been measured locally in order to study occasional variations that may occur. The proportion of other pollutants in the room air has been studied simultaneously with a gas chromatograph. Different types of CO₂ indicators were used to study the efficiency of the control system. The successful results indicate that the system can be used in new constructions, as well as in existing buildings.     

Experimental study of effectiveness of four radon mitigation solutions, based on underground depressurization, tested in prototype housing built in a high radon area in Spain

The present paper discusses the results of an empirical study of four approaches to reducing indoor radon concentrations based on depressurization techniques in underground sumps. The experiments were conducted in prototype housing built in an area of Spain where the average radon concentration at a depth of 1 m is 250 kBq m⁻³.Sump effectiveness was analysed in two locations: underneath the basement, which involved cutting openings into the foundation, ground storey and roof slabs, and outside the basement walls, which entailed digging a pit alongside the building exterior. The effectiveness of both sumps was likewise tested with passive and forced ventilation methods.The systems proved to be highly efficient, lowering radon levels by 91-99%, except in the solution involving passive ventilation and the outside sump, where radon levels were reduced by 53-55%. At wind speeds of over 8 m/s, however, passive ventilation across an outside sump lowered radon levels by 95% due to a Venturi effect induced drop in pressure.     

A longitudinal study relating carpeting with sick building syndrome

A longitudinal questionnaire study was performed among personnel in two Swedish primary schools with wall-to-wall carpets and four schools with hard floor covering. The study groups consisted of all primary schools equipped with wall-to-wall carpets in the town of Uppsala, plus a random sample of two newer and two elderly primary schools with hard floor covering. In an initial cross-sectional study, the wall-to-wall carpet group reported an enhanced prevalence of eye and airway symptoms, face rashes, headache, abnormal tiredness and a sensation of being electrostatically charged in comparison with personnel in schools with hard floor covering. Since the enhanced prevalence of symptoms in the wall-to-wall carpets versus the hard floor covering group was also observed among persons without signs of atopy it was concluded that wall-to-wall carpets are not exclusively a problem for the sensitive atopic individual. The type of ventilation system (mechanical ventilation versus natural ventilation) had no significant effect on the symptom frequencies. After the removal of the wall-to-wall carpets, many of the reported symptoms decreased to a level similar to the group without previous or present exposure to such carpets. However, the frequency of airway symptoms remained enhanced among the wall-to-wall carpet group.     

Seasonal variations of natural ventilation and radon-222 exhalation in a slightly rising dead-end tunnel

The concentration activity of radon-222 has been monitored, with some interruptions, from 1997 to 2005 in the end section of a slightly rising, dead-end, 38-m long tunnel located in the Phulchoki hill, near Kathmandu, Nepal. While a high concentration varying from 6 x 10(3) Bq m(-3) to 10 x 10(3) Bq m(-3) is observed from May to September (rainy summer season), the concentration remains at a low level of about 200 Bq m(-3) from October to March (dry winter season). This reduction of radon concentration is associated with natural ventilation of the tunnel, which, contrary to expectations for a rising tunnel, takes place mainly from October to March when the outside air temperature drops below the average tunnel temperature. This interpretation is supported by temperature measurements in the atmosphere of the tunnel, a few meters away from the entrance. The temporal variations of the diurnal amplitude of this temperature indeed follow the ventilation rate deduced from the radon measurements. In the absence of significant ventilation (summer season), the radon exhalation flux at the rock surface into the tunnel atmosphere can be inferred; it exhibits a yearly variation with additional transient reductions associated with heavy rainfall, likely to be due to water infiltration. No effect of atmospheric pressure variations on the radon concentration is observed in this tunnel. This experiment illustrates how small differences in the location and geometry of a tunnel can lead to vastly different behaviours of the radon concentration versus time. This observation has consequences for the estimation of the dose rate and the practicability of radon monitoring for tectonic purposes in underground environments.     

Fuel poverty increases risk of mould contamination,regardless of adult risk perception & ventilation in social housing properties

IntroductionFuel poverty affects 2.4 million UK homes leading to poor hygrothermal conditions and risk of mould and house dust mite contaminations, which in turn increases risk of asthma exacerbation. For the first time we assess how fuel poverty, occupants' risk perception and use of mechanical ventilation mediate the risk of mould contamination in social housing.MethodsPostal questionnaires were sent to 3867 social housing properties to collect adult risk perception, and demographic and environmental information on occupants. Participant details were linked to data pertaining to the individual properties. Multiple logistic regression was used to calculate odds ratios and confidence intervals while allowing for clustering of individuals coming from the same housing estate. We used Structured Equation Modelling and Goodness of Fit analysis in mediation analyses to examine the role of fuel poverty, risk perception, use of ventilation and energy efficiency.ResultsEighteen percent of our target social housing populations (671 households) were included into our study. High risk perception (score of 8–10) was associated with reduced risk of mould contamination in the bedrooms of children (OR 0.5 95% CI; 0.3–0.9) and adults (OR 0.4 95% CI; 0.3–0.7). High risk perception of living with inadequate heating and ventilation reduced the risk of mould contamination (OR 0.5 95% CI; 0.3–0.8 and OR 0.5 95% CI; 0.3–0.7, respectively). Participants living with inadequate heating and not heating due to the cost of fuel had an increased risk of mould contamination (OR 3.4 95% CI; 2.0–5.8 and OR 2.2 95% CI; 1.5–3.2, respectively). Increased risk perception and use of extractor fans did not mediate the association between fuel poverty behaviours and increased risk of mould contamination.DiscussionFuel poverty behaviours increased the risk of mould contamination, which corresponds with existing literature. For the first time we used mediation analysis to assess how this association maybe modified by occupant behaviours. Increased risk perception and use of extractor fans did not modify the association between fuel poverty and mould contamination. This suggests that fuel poor populations may not benefit from energy efficiency interventions due to ineffective heating and ventilation practices of those occupants residing participating households. Our findings may be modified by a complex interaction between occupant behaviours and the built environment. We found that participant age, occupancy, SES, pets, drying washing indoors, geographic location, architectural design/age of the property, levels of insulation and type of heating regulated risk of mould contamination.ConclusionFuel poverty behaviours affected around a third of participating households and represent a risk factor for increased exposures to damp and mouldy conditions, regardless of adult risk perception, heating and ventilation practices. This requires multidisciplinary approach to assess the complex interaction between occupant behaviours, risk perception, the built environment and the effective use of heating and ventilation practices.Study implicationsOur findings have implications for housing policies and future housing interventions. Effective communication strategies focusing on awareness and perception of risk may help address indoor air quality issues. This must be supported by improved household energy efficiency with the provision of more effective heating and ventilation strategies, specifically to help alleviate those suffering from fuel poverty.