Volatile organic pollutants in new and established buildings in Melbourne, Australia

Volatile organic compounds (VOCs) within new and established buildings have been determined and factors significant to their presence have been identified. In established dwellings, total volatile organic compound (TVOC) concentrations were low, but were approximately four times higher than in outdoor air, showing a dominant effect of indoor sources. The presence of attached garages, site contamination and 'faulty' wool carpet were associated with higher indoor pollution. In three dwellings, unidentified sources of benzene were indicated. Much higher VOC concentrations were observed in new or renovated buildings, persisting above "baseline" levels for several weeks, concentration decay rate correlating with VOC molecular volume, indicating emissions were limited by material diffusion processes. VOC and formaldehyde emission decays in a new dwelling occurred by a double-exponential source model. This shows that persistent low levels of volatile organic pollutants in established dwellings can occur due to long-term emissions from building materials.     

The MERMAID study: indoor and outdoor average pollutant concentrations in 10 low‐energy school buildings in France

Indoor air quality was characterized in 10 recently built energy‐efficient French schools during two periods of 4.5 days. Carbon dioxide time‐resolved measurements during occupancy clearly highlight the key role of the ventilation rate (scheduled or occupancy indexed), especially in this type of building, which was tightly sealed and equipped with a dual‐flow ventilation system to provide air refreshment. Volatile organic compounds (VOCs) and inorganic gases (ozone and NO₂) were measured indoors and outdoors by passive techniques during the occupied and the unoccupied periods. Over 150 VOC species were identified. Among them, 27 species were selected for quantification, based on their occurrence. High concentrations were found for acetone, 2‐butanone, formaldehyde, toluene, and hexaldehyde. However, these concentrations are lower than those previously observed in conventional school buildings. The indoor/outdoor and unoccupied/occupied ratios are informative regarding emission sources. Except for benzene, ozone, and NO₂, all the pollutants in these buildings have an indoor source. Occupancy is associated with increased levels of acetone, 2‐butanone, pentanal, butyl acetate, and alkanes.     

Do time‐averaged,whole‐building,effective volatile organic compound (VOC) emissions depend on the air exchange rate? A statistical analysis of trends for 46 VOCs in U.S. offices

We used existing data to develop distributions of time‐averaged air exchange rates (AER), whole‐building ‘effective’ emission rates of volatile organic compounds (VOC), and other variables for use in Monte Carlo analyses of U.S. offices. With these, we explored whether long‐term VOC emission rates were related to the AER over the sector, as has been observed in the short term for some VOCs in single buildings. We fit and compared two statistical models to the data. In the independent emissions model (IEM), emissions were unaffected by other variables, while in the dependent emissions model (DEM), emissions responded to the AER via coupling through a conceptual boundary layer between the air and a lumped emission source. For 20 of 46 VOCs, the DEM was preferable to the IEM and emission rates, though variable, were higher in buildings with higher AERs. Most oxygenated VOCs and some alkanes were well fit by the DEM, while nearly all aromatics and halocarbons were independent. Trends by vapor pressure suggested multiple mechanisms could be involved. The factors of temperature, relative humidity, and building age were almost never associated with effective emission rates. Our findings suggest that effective emissions in real commercial buildings will be difficult to predict from deterministic experiments or models.     

Real‐world volatile organic compound emission rates from seated adults and children for use in indoor air studies

Human beings emit many volatile organic compounds (VOCs) of both endogenous (internally produced) and exogenous (external source) origin. Here we present real‐world emission rates of volatile organic compounds from cinema audiences (50‐230 people) as a function of time in multiple screenings of three films. The cinema location and film selection allowed high‐frequency measurement of human‐emitted VOCs within a room flushed at a known rate so that emissions rates could be calculated for both adults and children. Gas‐phase emission rates are analyzed as a function of time of day, variability during the film, and age of viewer. The average emission rates of CO₂, acetone, and isoprene were lower (by a factor of ~1.2‐1.4) for children under twelve compared to adults while for acetaldehyde emission rates were equivalent. Molecules influenced by exogenous sources such as decamethylcyclopentasiloxanes and methanol tended to decrease over the course of day and then rise for late evening screenings. These results represent average emission rates of people under real‐world conditions and can be used in indoor air quality assessments and building design. Averaging over a large number of people generates emission rates that are less susceptible to individual behaviors.     

Reflections on the history of indoor air science,focusing on the last 50 years

The scientific articles and Indoor Air conference publications of the indoor air sciences (IAS) during the last 50 years are summarized. In total 7524 presentations, from 79 countries, have been made at Indoor Air conferences held between 1978 (49 presentations) and 2014 (1049 presentations). In the Web of Science, 26 992 articles on indoor air research (with the word “indoor” as a search term) have been found (as of 1 Jan 2016) of which 70% were published during the last 10 years. The modern scientific history started in the 1970s with a question: “did indoor air pose a threat to health as did outdoor air?” Soon it was recognized that indoor air is more important, from a health point of view, than outdoor air. Topics of concern were first radon, environmental tobacco smoke, and lung cancer, followed by volatile organic compounds, formaldehyde and sick building syndrome, house dust‐mites, asthma and allergies, Legionnaires disease, and other airborne infections. Later emerged dampness/mold‐associated allergies and today's concern with “modern exposures‐modern diseases.” Ventilation, thermal comfort, indoor air chemistry, semi‐volatile organic compounds, building simulation by computational fluid dynamics, and fine particulate matter are common topics today. From their beginning in Denmark and Sweden, then in the USA, the indoor air sciences now show increasing activity in East and Southeast Asia.     

Field‐to‐laboratory analysis of clay wall coatings as passive removal materials for ozone in buildings

Ozone reacts readily with many indoor materials, as well as with compounds in indoor air. These reactions lead to lower indoor than outdoor ozone concentrations when outdoor air is the major contributor to indoor ozone. However, the products of indoor ozone reactions may be irritating or harmful to building occupants. While active technologies exist to reduce indoor ozone concentrations (i.e, in‐duct filtration using activated carbon), they can be cost‐prohibitive for some and/or infeasible for dwellings that do not have heating, ventilating, and air‐conditioning systems. In this study, the potential for passive reduction of indoor ozone by two different clay‐based interior surface coatings was explored. These coatings were exposed to occupied residential indoor environments and tested bimonthly in environmental chambers for quantification of ozone reaction probabilities and reaction product emission rates over a 6‐month period. Results indicate that clay‐based coatings may be effective as passive removal materials, with relatively low by‐product emission rates that decay rapidly within 2 months.     

Contaminant levels,source strengths,and ventilation rates in California retail stores

This field study measured ventilation rates and indoor air quality in 21 visits to retail stores in California. Three types of stores, such as grocery, furniture/hardware stores, and apparel, were sampled. Ventilation rates measured using a tracer gas decay method exceeded the minimum requirement of California's Title 24 Standard in all but one store. Concentrations of volatile organic compounds (VOCs), ozone, and carbon dioxide measured indoors and outdoors were analyzed. Even though there was adequate ventilation according to standard, concentrations of formaldehyde and acetaldehyde exceeded the most stringent chronic health guidelines in many of the sampled stores. The whole‐building emission rates of VOCs were estimated from the measured ventilation rates and the concentrations measured indoor and outdoor. Estimated formaldehyde emission rates suggest that retail stores would need to ventilate at levels far exceeding the current Title 24 requirement to lower indoor concentrations below California's stringent formaldehyde reference level. Given the high costs of providing ventilation, effective source control is an attractive alternative.     

Quantifying fine particle emission events from time‐resolved measurements: Method description and application to 18 California low‐income apartments

PM_2.5 exposure is associated with significant health risk. Exposures in homes derive from both outdoor and indoor sources, with emissions occurring primarily in discrete events. Data on emission event magnitudes and schedules are needed to support simulation‐based studies of exposures and mitigations. This study applied an identification and characterization algorithm to quantify time‐resolved PM_2.5 emission events from data collected during 224 days of monitoring in 18 California apartments with low‐income residents. We identified and characterized 836 distinct events with median and mean values of 12 and 30 mg emitted mass, 16 and 23 minutes emission duration, 37 and 103 mg/h emission rates, and pseudo‐first–order decay rates of 1.3 and 2.0/h. Mean event‐averaged concentrations calculated using the determined event characteristics agreed to within 6% of measured values for 14 of the apartments. There were variations in event schedules and emitted mass across homes, with few events overnight and most emissions occurring during late afternoons and evenings. Event characteristics were similar during weekdays and weekends. Emitted mass was positively correlated with number of residents (Spearman coefficient, ρ=.10), bedrooms (ρ=.08), house volume (ρ=.29), and indoor‐outdoor CO₂ difference (ρ=.27). The event schedules can be used in probabilistic modeling of PM_2.5 in low‐income apartments.     

Spatial and temporal variability in VOC levels within a commercial retail building

A study was performed to characterize the concentration of dozens of volatile organic compounds (VOCs) at 10 locations within a single large building and track these concentrations over a 2-year period. The study was performed at a shopping center (strip mall) in New Jersey. A total of 130 indoor air samples were collected from 10 retail stores within the shopping center and analyzed for 60 VOCs by US EPA Method TO-15. Indoor concentrations of up to 55,100 microg/m(3) were measured for individual VOCs. The indoor/outdoor ratio (I/O) was as high as 1500 for acetone and exceeded 100 at times for various compounds, indicating that significant indoor air sources were present. A large degree of spatial variability was observed between stores within the building, with concentrations varying by three to four orders of magnitude for some compounds. The spatial variability was dependent on the proximity of the sampling locations to the indoor sources. A large degree of temporal variability also was observed for compounds emitted from indoor sources, but the temporal variability generally did not exceed two standard deviations (sigma). For compounds not emitted from indoor sources at significant rates, both the spatial and temporal variability tended to range within an order of magnitude at each location. PRACTICAL IMPLICATIONS: Many cross-sectional studies have been published where the levels of volatile organic compounds (VOCs) were measured in indoor air at one or two locations for houses or offices. This study provides longitudinal data for a commercial retail building and also addresses spatial variability within the building. The data suggest that spatial and temporal variability are important considerations for compounds emitted from indoor sources. Elevated concentrations were found in retail spaces with no apparent emission sources due to their proximity to other retail spaces with emission sources.     

Investigation of volatile organic compounds in office buildings in Bangkok,Thailand: Concentrations,sources, and occupant symptoms

To conserve energy, office buildings with air-conditioning systems in Thailand are operated with a tight thermal envelope. This leads to low fresh-air ventilation rates and is thought to be partly responsible for the sick building syndrome symptoms reported by occupants. The objectives of this study are to measure concentrations and to determine sources of 13 volatile organic compounds (VOCs) in office buildings with air-conditioning systems in the business area of Bangkok. Indoor and outdoor air samples from 17 buildings were collected on Tenax-TA^™ sorbent tubes and analyzed for individual VOCs by thermal desorption-gas chromatography/mass spectrometry (TD–GC/MS). Building ventilation was measured with a constant injection technique using hexafluorobenzene as a tracer gas. The results show that the VOC concentrations varied significantly among the studied buildings. The two most dominant VOCs were toluene and limonene with average concentrations of 110 and 60.5 μg m⁻³, respectively. A Wilcoxon sum rank test indicated that the indoor concentrations of aromatic compounds and limonene were statistically higher than outdoor concentrations at the 0.05 level, while the indoor concentrations of chlorinated compounds were not. Indoor emission factors of toluene and limonene were found to be highest with the average values of 80.9 and 18.9 μg m⁻² h⁻¹, respectively. Principal component analysis was applied to the emission factors of 13 VOCs, producing three components based on source similarities. Furthermore, a questionnaire survey investigation and field measurements of building air exchange pointed to indoor air complaints related to inadequate ventilation.     

Particle‐associated polycyclic aromatic hydrocarbons in a representative urban location (indoor‐outdoor) from South Europe: Assessment of potential sources and cancer risk to humans

PM₁₀‐bound polycyclic aromatic hydrocarbons (PAHs) levels were monitored at urban locations (outdoor/indoor) within the city of Madrid between May 2017 and April 2018. Fourteen PAH congeners were measured, potential emission sources were identified as were potential carcinogenic risks. The ΣPAHs averaged 0.577 and 0.186 ng/m³ in outdoor and indoor air, with a high linear correlation per individual mean PAH and month. The largest contributors to the ΣPAHs were the high‐molecular‐weight PAHs. Principal component analysis‐multiple linear regression results showed that emissions from diesel and vehicular processes explained 27% and 23% of the total variance of outdoor and indoor air, while combustion processes accounted for 30% and 25% in ambient and indoor air, respectively. During the cold season, biomass burning plus coal and wood combustion were additional sources of outdoor emissions. The heavy‐, medium‐ and light‐molecular‐weight PAH originating from outdoor sources accounted for 72%, 80%, and ~60% of the indoor levels of the three respective PAH groups. Average BaP concentration was 0.029 and 0.016 ng/m³ in outdoor and indoor air, respectively. Estimated BaPeq concentration averaged 0.072, 0.035, and 0.027 ng/m³ for outdoor, indoor, and indoor‐generated individual PAH concentrations, respectively. The estimated carcinogenic risk falls within the range of acceptable risk targeted by the US‐EPA.     

The effect of temperature on the emission of formaldehyde and volatile organic compounds (VOCs) from laminate flooring — case study

The effect of temperatures of 23, 29, 50°C on formaldehyde and volatile organic compounds (VOCs) emission from laminate flooring Type A (with particleboard as substrate) and Type B (with high density fibre (HDF)) was examined. At 23 and 29°C the measurements did not show any emissions of formaldehyde and very low emissions of VOCs. At a temperature of 50°C, Type A showed a high initial emission of formaldehyde and VOCs, which decreased with time. The emission from Type B was much lower. In conclusion, some laminate flooring may affect the chemical contamination of indoor air with the use of floor heating.     

Application of proton‐transfer‐reaction‐mass‐spectrometry for Indoor Air Quality research

In the field of Indoor Air Quality research, the measurement of volatile organic compounds (VOCs) demands instruments that are rapid, mobile, robust, highly sensitive and allow for simultaneous monitoring of multiple compounds. These instruments should also compensate for possible interferences from permanent gases and air humidity. Proton‐transfer‐reaction‐mass‐spectrometry (PTR‐MS) has proved to be a valuable and promising technique that fits the mentioned requirements for a suitable online measuring device. In this study, five exemplary applications of PTR‐MS are described: (i) release of paint additives during drying process, (ii) emission of VOCs from active hardcopy devices, (iii) reference material evaluation, (iv) diffusion studies, and (v) emission testing of building products. The examples are selected to illustrate possibilities and limitations of the PTR technique in this field of research. The quadruple‐based PTR‐QMS was able to determine the emission characteristics during the experiments, especially in case of depleting emission sources (e.g., reference material). This allows for chemometrical analysis of the measured release patterns and detection of underlying processes. However, PTR‐QMS reaches a functional limit in case of compound identification. If identification of VOCs is necessary, the measurements need to be accompanied by GC/MS analytics or a PTR instrument with higher mass‐resolution (e.g., PTR‐TOF‐MS).     

A review of the emission of VOCs from polymeric materials used in buildings

Building and furnishing materials and consumers products are important sources of formaldehyde and other volatile organic compounds (VOCs) in the indoor environment. The emission from materials is usually continuous and may last for many years in a building. The available evidence indicates that VOCs can cause adverse health effects to the building occupants and may contribute to symptoms of ‘Sick Building Syndrome’.

Control of VOC emission should increasingly become an important consideration for the design and manufacture of polymeric materials used in buildings. The EC Construction Products Directive ‘Essential Requirements’ set a framework for limiting the use of materials that could pose a health risk to building occupants. Furthermore, the on-going development of voluntary labelling schemes and data bases of material emissions that could be used by building designers, should further strengthen the demand for ‘low VOC emitting’ products.

This paper reviews available information about the emission of VOCs from polymeric building materials, the level of emissions in the indoor environment and the requirements for testing of the materials.     

Sensory and chemical evaluation of odorous emissions from building products with and without linseed oil

Natural materials of biological origin degrade over time and may emit odorous chemical compounds that can influence the perceived indoor air quality. The objective of this study was to investigate how the perceived air quality is influenced by emissions from building products with linseed oil compared with similar conventional synthetic products without linseed oil. Two types of linoleum, two types of wall paint and two types of floor oil were selected as examples of natural products containing linseed oil. The selected synthetic products were PVC floor covering, a water-based paint, and a synthetic floor oil. The emissions from the products were monitored over a one-year period in small ventilated test chambers. The odorous emissions were evaluated by sensory panel assessments of odour intensity and acceptability and by chemical analysis of the odour-active volatile organic compounds (VOCs) and carbonyl compounds. Odour-active VOCs in the emissions from one floor oil with linseed oil and two pure linseed oils were detected by gas chromatography combined with olfactometry (GC-O) and attempted identified with mass spectrometry (MS). The products with linseed oil influenced the perceived air quality more negatively than the similar synthetic products and the odour was persistent over time. It was found that the products with linseed oil did not qualify for the Danish Indoor Climate Label, because of the persistency of the odour. The results of the GC-O/MS investigations and VOC measurements indicated that an almost constant emission of odour-active VOCs with low odour thresholds resulted in the persistency of the odour. The VOCs probably originated from oxidation products from the linseed oil used as raw material. The study indicates that the acceptability of the emissions from the floor oil was influenced by the linseed oil used as raw material. It is therefore suggested that systematic use of less odorous linseed oils may improve the acceptability of the emission from products with linseed oils. The applied combination of sensory assessment of perceived air quality and GC-O/MS seems to be a useful approach in the effort to eliminate unwanted odours from building products.     

How to measure and evaluate volatile organic compound emissions from building products. A perspective

The primary emissions of VOCs (e.g. solvents) from building products influence the perceived indoor air quality during the initial decay period. However, secondary emissions will continue thereafter (chemical or physical degradation, e.g. oxidation, hydrolysis, mechanical wear, maintenance), in addition to sorption processes. Emission testing for primary VOC emissions is necessary, but insufficient to characterise the impact of building products in their entire life span on the perceived air quality. Methods to distinguish between the two types of emissions are required. Also, the influence of climate parameters on the emission rates is necessary to know for proper testing. Future product development and selection strategies of new building products should consider the secondary emissions, in addition to the contribution from the use of auxiliary agents for cleaning, maintenance, and other potential impacts either physical or chemical in nature. Some of the requirements for emission testing are discussed in terms of secondary vs. primary emissions in order to develop 'healthier/better' building products for the indoor environment. In addition, some of the assumptions about the possible impact of VOCs on health and comfort in the indoor environment are presented. Odour thresholds for VOCs are one or more orders of magnitude lower than the corresponding airway irritation estimates, and it also appears that chemically non-reactive VOCs are not sufficiently strong irritants to cause airway irritation at concentrations normally encountered indoors. Finally, future requirements for analytical laboratory performances is proposed to accommodate the increasing need to establish which VOCs may be responsible for the perception of odour intensity from building products.     

Analysis of indoor particles and gases and their evolution with natural ventilation

The air composition and reactivity from outdoor and indoor mixing field campaign was conducted to investigate the impacts of natural ventilation (ie, window opening and closing) on indoor air quality. In this study, a thermal desorption aerosol gas chromatograph (TAG) obtained measurements of indoor particle‐ and gas‐phase semi‐ and intermediately volatile organic compounds both inside and outside a single‐family test home. Together with measurements from a suite of instruments, we use TAG data to evaluate changes in indoor particles and gases at three natural ventilation periods. Positive matrix factorization was performed on TAG and adsorbent tube data to explore five distinct chemical and physical processes occurring in the indoor environment. Outdoor‐to‐indoor transport is observed for sulfate, isoprene epoxydiols, polycyclic aromatic hydrocarbons, and heavy alkanes. Dilution of indoor species is observed for volatile, non‐reactive species including methylcyclohexane and decamethylcyclopentasiloxane. Window opening drives enhanced emissions of semi‐ and intermediately volatile species including TXIB, DEET, diethyl phthalate, and carvone from indoor surfaces. Formation via enhanced oxidation was observed for nonanal and 2‐decanone when outdoor oxidants entered the home. Finally, oxidative depletion of gas‐phase terpenes (eg, limonene and α‐pinene) was anticipated but not observed due to limited measurement resolution and dynamically changing conditions.     

Emissions of volatile organic compounds from polymer-based consumer products: Comparison of three emission chamber sizes

The ISO 16000 standard series provide guidelines for emission measurements of volatile organic compounds (VOCs) from building materials. However, polymer-based consumer products such as toys may also release harmful substances into indoor air. In such cases, the existing standard procedures are unsuitable for official control laboratories due to high costs for large emission testing chambers. This paper aims at developing and comparing alternative and more competitive methods for the emission testing of consumer products. The influence of the emission chamber size was investigated as smaller chambers are more suited to the common size of consumer products and may help to reduce the costs of testing. Comparison of the performance of a 203 L emission test chamber with two smaller chambers with the capacity of 24 L and 44 mL, respectively, was carried out by using a polyurethane reference material spiked with 14 VOCs during the course of 28 days. The area-specific emission rates obtained in the small chambers were always similar to those of the 203 L reference chamber after a few hours. This implies that smaller chambers can provide at least useful numbers on the extent of polymer-based consumer product emissions into indoor air, thereby supporting meaningful exposure assessments.     

Characterization of Linoleum. Part 1: Measurement of Volatile Organic Compounds by use of the Field and Laboratory Emission Cell, “FLEC”⋆

The volatile organic compounds (VOCs) emitted from 12 linoleum samples were measured by use of the “Field and Laboratory Emission Cell” (FLEC) with sampling on Tenax TA followed by thermal desorbtion and GC/FID or GC/MS analysis. Major VOCs were alkanals, alkenals and fatty acids. The emissions were measured after 24 h in FLEC and again after one month's storage in a well ventilated room. The emission profiles of hexanal, nonanal and propanoic acid were modeled for four linoleum samples using a new exponential diffusion model. The time required to reach 50% of the odor threshold concentrations in a standard room was from 113 to 2296 hours. The applicability of the diffusion model for modeling long-term emission needs to be further evaluated considering possible continuous oxidative emission.