Volatile organic compound concentrations and emission rates measured over one year in a new manufactured house

A study to measure indoor concentrations and emission rates of volatile organic compounds (VOCs), including formaldehyde, was conducted in a new, unoccupied manufactured house installed at the National Institute of Standards and Technology (NIST) campus. The house was instrumented to continuously monitor indoor temperature and relative humidity, heating and air conditioning system operation, and outdoor weather. It also was equipped with an automated tracer gas injection and detection system to estimate air change rates every 2 h. Another automated system measured indoor concentrations of total VOCs with a flame ionization detector every 30 min. Active samples for the analysis of VOCs and aldehydes were collected indoors and outdoors on 12 occasions from August 2002 through September 2003. Individual VOCs were quantified by thermal desorption to a gas chromatograph with a mass spectrometer detector (GC/MS). Formaldehyde and acetaldehyde were quantified by high performance liquid chromatography (HPLC). Weather conditions changed substantially across the twelve active sampling periods. Outdoor temperatures ranged from 7 C to 36 C. House air change rates ranged from 0.26 h{sup -1} to 0.60 h{sup -1}. Indoor temperature was relatively constant at 20 C to 24 C for all but one sampling event. Indoor relative humidity (RH) ranged from 21% to 70%. The predominant and persistent indoor VOCs included aldehydes (e.g., formaldehyde, acetaldehyde, pentanal, hexanal and nonanal) and terpene hydrocarbons (e.g., a-pinene, 3-carene and d-limonene), which are characteristic of wood product emissions. Other compounds of interest included phenol, naphthalene, and other aromatic hydrocarbons. VOC concentrations were generally typical of results reported for other new houses. Measurements of total VOCs were used to evaluate short-term changes in indoor VOC concentrations. Most of the VOCs probably derived from indoor sources. However, the wall cavity was an apparent source of acetaldehyde, toluene and xylenes and the belly space was a source of 2-butanone, lower volatility aldehydes and aromatic hydrocarbons. Indoor minus outdoor VOC concentrations varied with time. Adjusted formaldehyde concentrations exhibited the most temporal variability with concentrations ranging from 25 {micro}g m{sup -3} to 128 {micro}g m{sup -3} and the lowest concentrations occurring in winter months when indoor RH was low. A model describing the emissions of formaldehyde from urea-formaldehyde wood products as a function of temperature, RH and concentration reasonably predicted the temporal variation of formaldehyde emissions in the house. Whole-house emissions of other VOCs generally declined over the first three months and then remained relatively constant over a several month period. However, their emissions were generally lowest during the winter months. Also, an apparent association between TVOC emissions and outdoor temperature was observed on a one-week time scale

Ultrafine Particle Removal and Ozone Generation by In-Duct Electrostatic Precipitators

Human exposure to airborne ultrafine particles (UFP, < 100 nm) has been shown to have adverse health effects and can be elevated in buildings. In-duct electrostatic precipitator filters (ESP) have been shown to be an effective particulate control device for reducing UFP concentrations (20–100 nm) in buildings, although they have the potential to increase indoor ozone concentrations. This study investigated residential ESP filters to reduce ultrafine particles between 4 to 15 nm and quantified the resulting ozone generation. In-duct ESPs were operated in the central air handling unit of a test house. Results for the two tested ESP brands indicate that removal efficiency of 8 to 14 nm particles was near zero and always less than 10% (±15%), possibly due to particle generation or low charging efficiency. Adding a media filter downstream of the ESP increased the decay rate for particles in the same size range. Continuous operation of one brand of ESP raised indoor ozone concentrations to 77 ppb_v and 20 ppb_v for a second brand. Using commercial filters containing activated carbon downstream of the installed ESP reduced the indoor steady-state ozone concentrations between 6% and 39%

Indoor Ultrafine Particles of Outdoor Origin: Importance of Window Opening Area and Fan Operation Condition

Inhalation exposure to ambient ultrafine particles (UFP) has been shown to induce adverse health effects such as respiratory and cardiovascular mortality. Human exposure to particles of outdoor origin often occurs indoors due to entry of UFP into buildings. The objective of the present study is to investigate entry of UFP into a building considering building operational characteristics and their size-dependent effects on UFP concentrations. Indoor and outdoor UFP concentrations along with air change rates were continuously measured in a full-scale test building. Estimates of infiltration factor, penetration coefficient, and deposition rate have been made for a range of particle sizes from 4 to 100 nm. The results show that UFP infiltration factor varies with particle diameter, window position, air change rate, and central fan operation. When the central fan was on continuously, the average infiltration factor ranged from 0.26 (particles <10 nm) to 0.82 (particles >90 nm) for two large window openings, and from 0.07 to 0.60 for two small window openings. Under the central fan-off condition, the average infiltration factor ranged from 0.25 (particles <10 nm) to 0.72 (particles >90 nm) for two small window openings, while it ranged from 0.01 to 0.48 with all windows closed. Larger window openings led to higher infiltration factors due to the larger extent of particle penetration into the building. The fan operation mode (on vs off) also has a strong impact, as the infiltration factor was consistently lower (up to 40%) when the fan was on due to additional particle deposition loss to the furnace filter and duct surfaces

Standard Formaldehyde Source for Chamber Testing of Material Emissions: Model Development, Experimental Evaluation, and Impacts of Environmental Factors

Formaldehyde, which is recognized as a harmful indoor air pollutant for human health, is emitted mainly from urea-formaldehyde resin in wood products. Chamber tests are used to evaluate formaldehyde emission rates from these products. However, there is no available formaldehyde standard reference emission source to assess the performance of chamber testing systems. In this work, a LIFE (liquid-inner tube diffusion-film-emission) formaldehyde reference is described. The formaldehyde source consists of a polytetrafluoroethene (PTFE) tube that holds a formaldehyde–water solution with a concentration of 16 g formaldehyde per 100 mL water, with a thin polydimethylsiloxane (PDMS) film cover. Formaldehyde emission parameters for the PDMS film (diffusion coefficient and partition coefficient) were determined experimentally, thereby enabling the prediction of the formaldehyde emissions from the source for use as a reference value in a chamber. Chamber tests were conducted in a 51 L stainless steel ventilated chamber. The impacts of temperature and relative humidity on the emissions were investigated. Results show the LIFE’s chamber test results match those predicted by a mass transfer model. As a result, this formaldehyde source may be used to generate a reference concentration in product emission testing chambers, thereby providing a powerful tool to evaluate the performance of the chamber testing systems

Protection Against Airborne Chemical and Biological Releases

Due to concerns about potential airborne chemical and biological (chembio) releases in or near buildings, building owners and managers and other decision makers are considering retrofitting buildings to provide some degree of protection against such events. A wide range of technologies and approaches are being proposed with varying levels of efficacy and cost, as well as varying degrees of applicability to particular buildings and ventilation systems. This document presents the results of an effort to evaluate chembio retrofit options for buildings. A number of retrofit options are identified, and their potential to protect building occupants from a number of generic contaminant releases is evaluated, using building airflow and contaminant transport modeling. In addition, a case study is presented in which specific retrofit options were considered for two actua

40 years to build tight and ventilate right : from infiltration to smart ventilation : AIVC Technical note 70

As the AIVC was created in 1979, the 40th anniversary of the AIVC was celebrated in October 2019 at the 40th AIVC conference in Ghent. In the context of this celebration, it was decided to publish 2 overview publications: An AIVC technote, which focuses on the overall history of the AIVC and those involved in the organisation (TN 69: 40 years to build tight and ventilate right: History of the AIVC) This publication, focusing on the main technical areas of AIVC's involvement during the past 40 years The AIVC was created in 1979 and started having annual conferences in 1980. The 2019 Conference was its 40th conference and the conference theme focused on its anniversary. This Technical Note is a compendium of the contributions that the AIVC has made in its first 40 years and reflects field’s evolution over time. Much of the information generated by the AIVC is of direct use today and some of the older material is good source material for future research. The AIVC is an information dissemination project created by the International Energy Agency (IEA) as a result of a need to understand the energy impacts from air leakage in buildings for the energy crisis of the 1970s. When the Center was first created it was called the Air Infiltration Center because the focus was on energy loss due to infiltration. It was generally thought that most buildings leaked way too much air and that reducing that infiltration would reduce dependence of fossil fuels. The mechanism the IEA uses to create projects is through implementing agreements of member nations. The AIC was the 5th project (or “annex”) created by the implementing agreement on buildings and community systems, which has been renamed Energy in Buildings and Communities (EBC) at https://www.iea-ebc.org/. There have been 70 projects completed from EBC and 17 that are on-going currently. Of those, Annex V is the only information dissemination center and the only one that is active for more than a few years. Because infiltration research was not a field of its own in the 70s, the AIC became the de-facto coordinating body for infiltration-related research around the world. It was sometimes difficult to understand each other, hence we started a series of TN named AIRGLOSS in which terms and definitions were described. When investigating a new area, the first thing one must do is be able to measure it. A significant effort was put into measurement techniques both for air change rate and for air tightness. The research community is much broader now, but these are still active areas of research. Chapter 3 discusses air tightness and Chapter 4 discusses air flow measurement techniques. Infiltration and air tightness are of course related, but quantitatively connecting air leakage and air flow, requires modeling and such models did not really exist. So along with a focus on measurement techniques, the AIC worked on infiltration modeling as discussed in Chapter 5. The first models were simple, physical models, but as computing power and the state of knowledge grew, so did the models. After only a few years, it became clear that looking at infiltration in isolation was a sub-optimal approach. As buildings were getting tighter, there was a concern of insufficient air exchange. An optimal energy solution would then need to include both infiltration and designed ventilation. Accordingly, annex V’s mandate was broadened to include ventilation systems and in the mid-80s the name was changed to the Air Infiltration and Ventilation Center as it remains. In 1985 the AIVC began publishing technical reports (e.g. TN 17) that specifically focused on optimal ventilation strategies. Many AIVC (and conference publications) have worked this problem in the last 35 years. Chapters 14 and 15 review many of the approaches used today. One of the more recent trends is to make our ventilation systems smarter and Chapter 13 looks at some aspects of that. It was also realized during the 1980s that occupant behavior had a bit impact with respect to ventilation overall. EBC Annex VIII focused on this and resulted in 1988 in AIVC TN23 on the topic. Early research focused on issues such as window opening, but later work looked at how mechanical systems are perceived and ran. Chapter 10 looks at occupant impacts from today’s perspective. Ventilation for acceptable indoor air quality generally uses energy to condition the outdoor air, but there are times when ventilation can save energy, if it displaces the need for mechanical cooling. Providing ventilative cooling can be through both mechanical and natural means and can positively impact comfort. Chapter 8 discusses these issues. As the AIVC was going to work on optimal ventilation strategies, it was important to know what the standards for acceptable ventilation were and this became another focus of the center’s work. The center has published many documents related to standards such at TN26 in 1989 that summarized EBC Annex IX. Ventilation standards have grown much more sophisticated since those times and are addressed in Chapter 9. One thing common to most ventilation standards over that period is that they assume that outdoor air is clean, or at least substantially better than indoor air. In such a case one can use it to dilute indoor-generated contaminants without worry. We know that in many cases this assumption is wrong, but it is not always clear what to do. Chapter 12 looks at the issue of outdoor air more broadly. Outdoor air contains moisture, but water vapor is a rather unique kind of contaminant: it has both an indoor and outdoor source and we neither want too much of it nor too little. Control of moisture has been a priority for the AIVC since it had a workshop in New Zealand (TN20) in 1987. Chapter 7 provides an overview the issue today. Another unique kind of constituent is carbon dioxide. CO2 is a product of combustion including human metabolism and therefore is unavoidable in indoor spaces. At high enough concentrations CO2 can become deadly, but it is not a contaminant of concern in typical buildings. It is, however, a good indicator that can be used in ventilation systems. Use and misuse of CO2 is a quite topical issue today. Chapter 11 discusses the role of CO2 in buildings. Since the turn of the century, it has been clear that the purpose of ventilation is acceptable indoor air quality and one cannot determine acceptable indoor air quality without looking at health. A growing part of the more recent efforts of the AIVC have been focused on understanding this health linkage and optimizing systems accordingly. Chapters 6 and 13 address what the AIVC has been doing in this area and form a basis for future activities