Winter thermal comfort and indoor air quality in Swedish grade school classrooms, as assessed by the children

This paper presents results from a pilot thermal comfort study in five Swedish grade school classrooms in three different buildings during winter 2015/16. The study includes measurements of environmental parameters (air temperature, globe temperature, relative humidity, air speed, CO2) and questionnaire surveys designed to match the children’s cognitive level. The questionnaire includes questions about thermal perception, air quality and air movement, as well as the children’s clothing level. The aim of this study is to investigate whether recently found differences in thermal sensation between children and adults outside the heating season also apply to the winter season. Children’s assessment is compared to the objective measurements during the surveys, to winter design criteria for school classrooms and to comfort temperatures from previous studies. The results agree with the previously found warmer sensation of children compared to adults’ predicted thermal sensation based on the currently used PMV model, although this time the difference is smaller. Regarding air quality, no relationship was found between children’s assessment and CO2 levels

Size-resolved simulation of particulate matters and CO2 concentration in passenger vehicle cabins

The main aim of this study is to develop a mathematical size-dependent vehicle cabin model for particulate matter concentration including PM2.5\ua0(particles of aerodynamic diameter less than 2.5\ua0μm) and UFPs (ultrafine particles of aerodynamic diameter less than 100\ua0nm), as well as CO2\ua0concentration. The ventilation airflow rate and cabin volume parameters are defined from a previously developed vehicle model for climate system design. The model simulates different filter statuses, application of pre-ionization, different airflow rates and recirculation degrees. Both particle mass and count concentration within 10–2530\ua0nm are simulated. Parameters in the model are defined from either available component test data (for example filter efficiencies) or assumptions from corresponding studies (for example particle infiltration and deposition rates). To validate the model, road measurements of particle and CO2\ua0concentrations outside two vehicles were used as model inputs. The simulated inside PM2.5, UFP and CO2\ua0concentration were compared with the inside measurements. Generally, the simulation agrees well with measured data (Person’s\ua0r\ua00.89–0.92), and the simulation of aged filter with ionization is showing higher deviation than others. The simulation using medium airflows agrees better than the simulation using other airflows, both lower and higher. The reason for this may be that the filter efficiency data used in the model were obtained at airflows close to the medium airflow. When all size bins are compared, the sizes of 100–300\ua0nm were slightly overestimated. The results indicated that among others, expanded filter efficiency data as a function of filter ageing and airflow rate would possibly enhance the simulation accuracy. An initial application sample study on recirculation degrees presents the model’s possible application in developing advanced climate control strategies

The effectiveness of portable air cleaners against tobacco smoke in multizone residential environments

The purpose of this study was to investigate how the effectiveness of portable air cleaners (ACs) against tobacco smoke is influenced by the clean air delivery rate (CADR), the location of the AC in relation to the pollution source and the apartment structure. The study was based on field experiments and simulations with the CONTAM software. The AC effectiveness was about 80% for one AC, and 93% for two ACs in the studied apartment (volume=110m3). Ultrafine particles (UFP) exposure in a room without tobacco smoking (clean room) could be much less than in the source room if these rooms were not directly connected with each other (but indirectly connected via doors open to other rooms). Operating the AC in one of the rooms without cigarette smoking could develop a partly isolated clean environment. However, this led to a rather low cleaning effectiveness for the concentration of ultrafine particles in the apartment as a whole. If operating the AC in the room where cigarettes are being smoked, the UFP exposure in the whole apartment can be further reduced

Indoor Air Quality in energy-efficient buildings in Sweden: comparison with the Swedish residential housing stock and new conventional buildings

The aim of this study was to compare the indoor air quality in newly built energy-efficient (passive) buildings in Sweden with the Swedish residential housing stock and new conventional buildings. We have used data from our previous publications to calculate Indoor Environmental Index (IEI), which is an average of Indoor Discomfort Index (IDI) that regards temperature and relative humidity, and Indoor Air Pollution Index (IAPI) that regards concentrations of indoor air pollutants. The passive building had significantly worse IEQ than the housing stock (p <0.05). Further disentangling of the partial indexes revealed that the difference was almost entirely caused by low to very low relative humidity in the passive buildings which affected the IDI. It could be speculated that the low relative humidity is coupled to operation of the ventilation systems and air exchange rates. It might be of importance to review the ventilation requirements in the energy-efficient building

Vehicle cabin air quality – influence of air recirculation on energy use, particles and CO2

In this study simulations were performed to investigate the influence of different vehicle climate ventilation strategies, mainly the air recirculation (REC) degree, on the cabin air quality and climate system power. The focus of air quality is on the cabin particle concentrations including PM2.5 (particles of aerodynamic diameter less than 2.5 μm), UFP (ultrafine particles of aerodynamic diameter less than 100 nm), and cabin CO2 concentration. Three outside climates (cold, intermediate, and warm) and three outside particle concentrations are studied. The studied vehicle originally shows possibilities to meet WHO PM2.5 guideline of 15 μg/m3 with a new filter. The aged filter have reduced performance, especially when outside concentration is high. Increased REC shows advantages in all the three climates in reducing particles and climate power for the studied vehicle. Application of 70% REC (70% of ventilation air is recirculated air) on average lowers PM2.5 by 55% and 39% for a new and aged filter respectively. 70% REC with a new filter reduces cabin PM2.5 below guideline of 15 μg/m3 in all conditions. The reduction of UFP counts results are generally similar to that of PM2.5. Increased REC also lessens the average climate system power by up to 27 % on average. When REC is increased, the cabin CO2 concentration arise accordingly, and the magnitude is relevant to the passengers. In all studied conditions with 1 passenger, 70% REC does not increase CO2 above the common guideline of 1000 ppm. 70% REC is not recommended with more than 1 passengers in cold and intermediate climate, and 2 passengers in warm climate. Besides, to avoid the potential windscreen fog risk in cold climate, REC should be avoided when passengers are more than 3.Except for constant REC values, a sample study investigates a dynamic control of the REC. It shows the possibility of continuously optimizing REC to reduce the climate power and particles, while maintaining the CO2 concentration below 1000 ppm. In warm climate with 1 passenger boarded, the average optimized REC is 90%, which in comparison with base case lead to 44% PM2.5 reduction and 12% climate power reduction

PM2.5 and ultrafine particles in passenger car cabins in Sweden and northern China—the influence of filter age and pre-ionization

The main aim of the study was to evaluate the influence of filter status (new and aged), pre-ionization, on the particle filtration in modern passenger cars. Measurements of in-cabin and outside PM2.5 (dp < 2.5 μm) concentration and UFP (ultrafine particle, dp < 100 nm) counts, to calculate I/O (indoor to outdoor) ratios, were performed. They were done at two locations, to study the influence of different outside conditions on the HVAC (heating, ventilation, and air-conditioning) system. The measurements were performed in two new cars, with similar HVAC systems and settings, using a new and an aged synthetic filter.\ua0 Furthermore, an ionization unit was installed upstream of the filter in both cars. This enabled the study of filter status, with and without ionization, under common driving conditions. The results show that the HVAC system performances were very similar at the two locations, with average I/O ratios of 0.35-0.40 without ionization and 0.15-0.20 with ionization applied, although the outside conditions were considerably different. Furthermore, the aged filter clearly worsened the filtration ability. Considering the corresponding average PM2.5 I/O ratios in one location as an example, the average for the new filter was 0.20 and 0.60 for the aged filter. The corresponding UFP I/O ratios were 0.24 and 0.57. Other findings are that the aged filter with ionization reached a performance close to the new filter (without ionization), and that increased ventilation airflow and decreased recirculation degree, as expected, led to an increase of I/O ratio for both particle sizes

Disordered Crystal Structure and Anomalously High Solubility of Radium Carbonate

XRD measurements of RaCO3 revealedthat it isnot isostructural with witherite, and direct-space ab initio modeling showed that the carbonate oxygens are highly disordered.It was found that the solubility of RaCO3 is unexpectedlyhigher than the solubility of witherite (log(10) K (sp) (0) = -7.5 and -8.56,respectively), supporting the disordered nature of RaCO3. EXAFS data revealed an ionic radius of Ra2+ of 1.55 & ANGS;. Radium is the only alkaline-earth metal which forms disorderedcrystals in its carbonate phase.Radium-226 carbonate was synthesized from radium-bariumsulfate ((Ra0.76Ba0.24SO4)-Ra-226) at room temperature and characterized by X-ray powder diffraction(XRPD) and extended X-ray absorption fine structure (EXAFS) techniques.XRPD revealed that fractional crystallization occurred and that twophases were formed the major Ra-rich phase, Ra(Ba)CO3, and a minor Ba-rich phase, Ba(Ra)CO3, crystallizingin the orthorhombic space group Pnma (no. 62) thatis isostructural with witherite (BaCO3) but with slightlylarger unit cell dimensions. Direct-space ab initio modeling shows that the carbonate oxygens in the major Ra(Ba)CO3 phase are highly disordered. The solubility of the synthesizedmajor Ra(Ba)CO3 phase was studied from under- and oversaturationat 25.1 & DEG;C as a function of ionic strength using NaCl as thesupporting electrolyte. It was found that the decimal logarithm ofthe solubility product of Ra(Ba)CO3 at zero ionic strength(log(10) K (sp) (0)) is-7.5(1) (2 & sigma;) (s = 0.05 g & BULL;L-1). This is significantly higher than the log(10) K (sp) (0) of witheriteof -8.56 (s = 0.01 g & BULL;L-1), supporting the disordered nature of the major Ra(Ba)CO3 phase. The limited co-precipitation of Ra2+ within witherite,the significantly higher solubility of pure RaCO3 comparedto witherite, and thermodynamic modeling show that the results obtainedin this work for the major Ra(Ba)CO3 phase are also applicableto pure RaCO3. The refinement of the EXAFS data revealsthat radium is coordinated by nine oxygens in a broad bond distancedistribution with a mean Ra-O bond distance of 2.885(3) & ANGS;(1 & sigma;). The Ra-O bond distance gives an ionic radius ofRa(2+) in a 9-fold coordination of 1.545(6) & ANGS; (1 & sigma;)

Disordered Crystal Structure and Anomalously High Solubility of Radium Carbonate

Radium-226 carbonate was synthesized from radium-barium sulfate (226Ra0.76Ba0.24SO4) at room temperature and characterized by X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) techniques. XRPD revealed that fractional crystallization occurred and that two phases were formed─the major Ra-rich phase, Ra(Ba)CO3, and a minor Ba-rich phase, Ba(Ra)CO3, crystallizing in the orthorhombic space group Pnma (no. 62) that is isostructural with witherite (BaCO3) but with slightly larger unit cell dimensions. Direct-space ab initio modeling shows that the carbonate oxygens in the major Ra(Ba)CO3 phase are highly disordered. The solubility of the synthesized major Ra(Ba)CO3 phase was studied from under- and oversaturation at 25.1 \ub0C as a function of ionic strength using NaCl as the supporting electrolyte. It was found that the decimal logarithm of the solubility product of Ra(Ba)CO3 at zero ionic strength (log10 Ksp0) is −7.5(1) (2σ) (s = 0.05 g\ub7L-1). This is significantly higher than the log10 Ksp0 of witherite of −8.56 (s = 0.01 g\ub7L-1), supporting the disordered nature of the major Ra(Ba)CO3 phase. The limited co-precipitation of Ra2+ within witherite, the significantly higher solubility of pure RaCO3 compared to witherite, and thermodynamic modeling show that the results obtained in this work for the major Ra(Ba)CO3 phase are also applicable to pure RaCO3. The refinement of the EXAFS data reveals that radium is coordinated by nine oxygens in a broad bond distance distribution with a mean Ra-O bond distance of 2.885(3) \uc5 (1σ). The Ra-O bond distance gives an ionic radius of Ra2+ in a 9-fold coordination of 1.545(6) \uc5 (1σ)