Indoor acids and bases.

Numerous acids and bases influence indoor air quality. The most abundant of these species are CO2 (acidic) and NH3 (basic), both emitted by building occupants. Other prominent inorganic acids are HNO3 , HONO, SO2 , H2 SO4 , HCl, and HOCl. Prominent organic acids include formic, acetic, and lactic; nicotine is a noteworthy organic base. Sources of N-, S-, and Cl-containing acids can include ventilation from outdoors, indoor combustion, consumer product use, and chemical reactions. Organic acids are commonly more abundant indoors than outdoors, with indoor sources including occupants, wood, and cooking. Beyond NH3 and nicotine, other noteworthy bases include inorganic and organic amines. Acids and bases partition indoors among the gas-phase, airborne particles, bulk water, and surfaces; relevant thermodynamic parameters governing the partitioning are the acid-dissociation constant (Ka ), Henry's law constant (KH ), and the octanol-air partition coefficient (Koa ). Condensed-phase water strongly influences the fate of indoor acids and bases and is also a medium for chemical interactions. Indoor surfaces can be large reservoirs of acids and bases. This extensive review of the state of knowledge establishes a foundation for future inquiry to better understand how acids and bases influence the suitability of indoor environments for occupants, cultural artifacts, and sensitive equipment

Particle Deposition in Ventilation Ducts: Connectors, Bends and Developing Turbulent Flow

In ventilation ducts the turbulent flow profile is commonly disturbed or not fully developed, and these conditions are likely to influence particle deposition to duct surfaces. Particle deposition rates at eight S-connectors, in two 90 degrees duct bends and in two ducts where the turbulent flow profile was not fully developed were measured in a laboratory duct system with both bare steel and internally insulated ducts with hydraulic diameters of 15.2 cm. In the bare-steel duct system, experiments with nominal particle diameters of 1, 3, 5, 9, and 16 mu m were conducted at each of three nominal air speeds: 2.2, 5.3, and 9.0 m/s. In the insulated duct system, deposition of particles with nominal diameters of 1, 3, 5, 8, and 13 mu m was measured at nominal air speeds of 2.2, 5.3 and 8.8 m/s. Fluorescent techniques were used to measure directly the deposition velocities of monodisperse fluorescent particles to duct surfaces. Deposition at S-connectors, in bends, and in straight ducts with developing turbulence was often greater than deposition in straight ducts with fully developed turbulence for equal particle sizes, air speeds, and duct surface orientations. Deposition rates at all locations were found to increase with an increase in particle size or air speed. High deposition rates at S-connectors resulted from impaction, and these rates were nearly independent of the orientation of the S-connector. Deposition rates in the two 90 degrees bends differed by more than an order of magnitude in some cases, probably because of the difference in turbulence conditions at the bend inlets. In straight sections of bare steel ducts where the turbulent flow profile was developing, the deposition enhancement relative to fully developed turbulence generally increased with air speed and decreased with downstream distance from the duct inlet. This enhancement was greater at the duct ceiling and wall than at the duct floor. In insulated ducts, deposition enhancement was less pronounced overall than in bare steel ducts. Trends that were observed in bare steel ducts were present, but weaker, in insulated ducts

Mathematical modeling of chemically reactive pollutants in indoor air

A general mathematical model is presented for predicting the concentrations of chemically reactive compounds in indoor air. The model accounts for the effects of ventilation, filtration, heterogeneous removal, direct emission, and photolytic and thermal chemical reactions. The model is applied to the induction of photochemically reactive pollutants into a museum gallery, and the predicted NO, NO_x-NO, and O_3 concentrations are compared to measured data. The model predicts substantial production of several species due to chemical reaction, including HNO_2, HNO_3, NO_3, and N_2O_5. Circumstances in which homogeneous chemistry may assume particular importance are identified and include buildings with glass walls, indoor combustion sources, and direct emission of olefins

Protection of Works of Art From Atmospheric Ozone

Assesses the colorfastness of organic colorants and watercolor pigments tested in atmospheric ozone. A summary of a full report of the Environmental Quality Laboratory, California Institute of Technology, Pasadena

Investigating CO2 Removal by Ca- and Mg-based Sorbents with Application to Indoor Air Treatment

Indoor carbon dioxide (CO 2 ) levels serve as an indicator of ventilation sufficiency in relation to metabolic effluents. Recent evidence suggests that elevated CO 2 exposure (with or without other bioeffluents) may cause adverse cognitive effects. In shelter-in-place (SIP) facilities, indoor CO 2 levels may become particularly elevated. This study evaluates four low-cost alkaline earth metal oxides and hydroxides as CO 2 sorbents for potential use in indoor air cleaning applications. Sorbents studied were MgO, Mg(OH) 2 , Ca(OH) 2 and commercially available soda lime. Uncarbonated sorbents characterized with nitrogen adsorption porosimetry showed BET surface areas in the 5.6–27 m 2 /g range. Microstructural analyses, including X-ray diffraction, thermogravimetric analysis and scanning electron microscopy confirmed the carbonation mechanisms and extent of sorption under environmental conditions typical of indoor spaces. Ca-based sorbents demonstrated higher extent of carbonation than Mg-based sorbents. Laboratory parameterizations, including rate constants ( k ) and carbonation yields ( y ), were applied in material balance models to assess the CO 2 removal potential of Ca-based sorbents in three types of indoor environments. Soda lime ( k = [2.2–3.6] × 10 −3 m 3 mol CO 2 −1 h −1 , y = 0.49–0.51) showed potential for effective use in SIP facilities. For example, CO 2 exposure in a modeled SIP facility could be reduced by 80% for an 8-h sheltering interval and to levels below 5000 ppm for an 8-h period with a practically sized air cleaner. Predicted effectiveness was more modest for bedrooms and classroom

Airborne Particles in Museums

Presents one in a series of research activities aimed at a better understanding of the origin and fate of air pollution within the built environment

Ozone Reductions Using Residential Building Envelopes

Ozone is an air pollutant with that can have significant health effects and a significant source of ozone in some regions of California is outdoor air. Because people spend the vast majority of their time indoors, reduction in indoor levels of ozone could lead to improved health for many California residents. Ozone is removed from indoor air by surface reactions and can also be filtered by building envelopes. The magnitude of the envelope impact depends on the specific building materials that the air flows over and the geometry of the air flow paths through the envelope that can be changes by mechanical ventilation operation. The 2008 Residential Building Standards in California include minimum requirements for mechanical ventilation by referencing ASHRAE Standard 62.2. This study examines the changes in indoor ozone depending on the mechanical ventilation system selected to meet these requirements. This study used detailed simulations of ventilation in a house to examine the impacts of different ventilation systems on indoor ozone concentrations. The simulation results showed that staying indoors reduces exposure to ozone by 80percent to 90percent, that exhaust ventilation systems lead to lower indoor ozone concentrations, that opening of windows should be avoided at times of high outdoor ozone, and that changing the time at which mechanical ventilation occurs has the ability to halve exposure to ozone. Future work should focus on the products of ozone reactions in the building envelope and the fate of these products with respect to indoor exposures

Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures.

It is important to improve our understanding of exposure to particulate matter (PM) in residences because of associated health risks. The HOMEChem campaign was conducted to investigate indoor chemistry in a manufactured test house during prescribed everyday activities, such as cooking, cleaning, and opening doors and windows. This paper focuses on measured size distributions of PM (0.001-20 μm), along with estimated exposures and respiratory-tract deposition. Number concentrations were highest for sub-10 nm particles during cooking using a propane-fueled stovetop. During some cooking activities, calculated PM2.5 mass concentrations (assuming a density of 1 g cm-3) exceeded 250 μg m-3, and exposure during the postcooking decay phase exceeded that of the cooking period itself. The modeled PM respiratory deposition for an adult residing in the test house kitchen for 12 h varied from 7 μg on a day with no indoor activities to 68 μg during a simulated day (including breakfast, lunch, and dinner preparation interspersed by cleaning activities) and rose to 149 μg during a simulated Thanksgiving day

Surface Emissions Modulate Indoor SVOC Concentrations through Volatility-Dependent Partitioning.

Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate diesters and siloxanes suggest that volatility-dependent partitioning processes modulate airborne SVOC concentrations through interactions with surface-laden condensed-phase reservoirs. Airborne concentrations of SVOCs with vapor pressures in the range of C13 to C23 alkanes were observed to be correlated with indoor air temperature. Observed temperature dependencies were quantitatively similar to theoretical predictions that assumed a surface-air boundary layer with equilibrium partitioning maintained at the air-surface interface. Airborne concentrations of SVOCs with vapor pressures corresponding to C25 to C31 alkanes correlated with airborne particle mass concentration. For SVOCs with higher vapor pressures, which are expected to be predominantly gaseous, correlations with particle mass concentration were weak or nonexistent. During primary particle emission events, enhanced gas-phase emissions from condensed-phase reservoirs partitioned to airborne particles, contributing substantially to organic particulate matter. An emission event related to oven-usage was inferred to deposit siloxanes in condensed-phase reservoirs throughout the house, leading to the possibility of reemission during subsequent periods with high particle loading