Steven J. Nabinger

Reduction of exposure to ultrafine particles by kitchen exhaust hoods: The effects of exhaust flow rates, particle size, and burner position

Cooking stoves, both gas and electric, are one of the strongest and most common sources of ultrafine particles (UFP) in homes. UFP have been shown to be associated with adverse health effects such as DNA damage and respiratory and cardiovascular diseases. This study investigates the effectiveness of kitchen exhaust hoods in reducing indoor levels of UFP emitted from a gas stove and oven. Measurements in an unoccupied manufactured house monitored size-resolved UFP (2 nm to 100 nm) concentrations from the gas stove and oven while varying range hood flow rate and burner position. The air change rate in the building was measured continuously based on the decay of a tracer gas (sulfur hexafluoride, SF(6)). The results show that range hood flow rate and burner position (front vs. rear) can have strong effects on the reduction of indoor levels of UFP released from the stove and oven, subsequently reducing occupant exposure to UFP. Higher range hood flow rates are generally more effective for UFP reduction, though the reduction varies with particle diameter. The influence of the range hood exhaust is larger for the back burner than for the front burner. The number-weighted particle reductions for range hood flow rates varying between 100 m(3)/h and 680 m(3)/h range from 31% to 94% for the front burner, from 54% to 98% for the back burner, and from 39% to 96% for the oven.

Validation of multizone IAQ model predictions for tracer gas in a townhouse

To provide additional validation data for the multizone airflow and contaminant model, CONTAMW, experiments were performed in an occupied three-storey townhouse in Reston, VA. A tracer gas, sulfur hexafluoride (SF6), was manually injected within one room of the house and the concentration of SF6 was then measured in nine rooms. This same process was then recreated in CONTAMW and the resulting predictions were statistically compared to the measured values. A total of 10 experiments were conducted and simulated between May 2000 and June 2001. In four cases, the heating and air-conditioning system fan was operating. SF6 was injected in the recreation room (basement level), the kitchen= dining room (main level) and the master bedroom (upstairs level). A statistical comparison of measurements and predictions was performed per ASTM D5157 (ASTM 1997) for all cases. Comparisons were made for overall zone average concentrations and individual zone transient concentrations. The results for zone average concentrations were very good with many cases meeting most or all of the D5157 criteria. Several cases showed a poor to fair correlation between average measurements and predictions due to discrepancies with a single zonemdashthe main floor bathroommdashbut excluding that zone resulted in these cases meeting or nearly meeting the D5157 criteria. Comparisons of individual zone transient concentrations were mixed with many good to excellent cases but also numerous fair to poor. Zones other than the bathroom had occasional poor comparisons between predictions and measurements but no consistent discrepancies. The predicted SF6 concentration averaged over all zones and cases was within 10% of the average measured concentration.

Airtightness, ventilation, and energy consumption in a manufactured house :: pre-retrofit results

A retrofit study is being conducted to investigate the airtightness, ventilation and energy impacts of tightening the exterior envelope and the heating and air conditioning system ductwork of a double section manufactured house. This report describes the results of the pre-retrofit assessment of building airtightness, ventilation, and energy consumption under both heating and cooling conditions. Measurements of building envelope airtightness and duct leakage were made using fan pressurization. Air change rates were measured continuously using the tracer gas decay technique. Energy consumption was monitored through measurement of gas consumption by the forced-air furnace for heating and electricity use by the air-conditioning system for cooling. After the pre-retrofit data collection was finished, the house underwent retrofits to tighten the building envelope and to reduce ventilation system duct leakage. After completion of the retrofits, post-retrofit data was collected. This report presents the results of the pre-retrofit measurements and a description of the retrofits.

Development of a field test method to evaluate gaseous air cleaner performance in a multizone building.

Abstract The performance of gaseous air cleaners for commercial and residential buildings has typically been evaluated using test protocols developed for a controlled laboratory chamber or a test duct. It is currently unknown how laboratory measurements relate to the actual performance of an air cleaner installed in a real building. However, to date, there are no air cleaner field test protocols available, thereby limiting the existing field data. The National Institute of Standards and Technology (NIST) has conducted a series of experiments to support test procedure development for evaluating the installed performance of gaseous air cleaning equipment, as well as metrics for characterizing field performance. To date, over 100 experiments have been completed, of which 23 portable air cleaner experiments and 6 in-duct air cleaner experiments are described in this paper. Tests were conducted in a finished three-bedroom/two-bathroom manufactured house equipped with several gas chromatographs to semi-continuously measure air change rates and volatile organic compound concentrations. Experimental variables included air cleaner location, isolation of zones by closing doors, and contaminant source location. For each experiment, air cleaner removal of decane was directly measured using the air cleaner inlet and outlet concentrations, as well as with mass balance analyses using measured room concentrations. With a verified mass balance model, a field performance metric was developed to compare installed whole-building performance to the performance predicted by a laboratory result. The results provide insight into the protocols and metrics that might prove useful for characterizing the field performance of air cleaners as well as the impact of air cleaner removal on zonal concentration levels in a variety of situations.

Characterization of Airborne Nanoparticle Released from Consumer Products

This letter report provides a project update reflecting the activities to date under the FY2012 interagency agreement between CPSC and NIST. The objective of that agreement is to develop testing and measurement protocols for determining the quantities and properties of nanoparticles released from flooring finishes and interior paints, including their subsequent airborne concentrations. This document focuses specifically on the project task titled Chamber Measurements of Airborne Nanoparticles, including the design of a chamber for measuring airborne concentrations of nanoparticles generated by abrasion flooring and paint samplers.

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.