Field evaluations of newly available "interference-free" monitors for nitrogen dioxide and ozone at near-road and conventional National Ambient Air Quality Standards compliance sites.

Unlabelled: Long-standing measurement techniques for determining ground-level ozone (O) and nitrogen dioxide (NO) are known to be biased by interfering compounds that result in overestimates of high O and NO ambient concentrations under conducive conditions. An increasing near-ground O gradient (NGOG) with increasing height above ground level is also known to exist. Both the interference bias and NGOG were investigated by comparing data from a conventional Federal Equivalent Method (FEM) O photometer and an identical monitor upgraded with an "interference-free" nitric oxide O scrubber that alternatively sampled at 2 m and 6.

High-end exposure relationships of volatile air toxics and carbon monoxide to community-scale air monitoring stations in Atlanta, Chicago, and Houston.

Evaporative and exhaust mobile source air toxic (MSAT) emissions of total volatile organic compounds, carbon monoxide, BTEX (benzene, toluene, ethylbenzene, and xylenes), formaldehyde, acetaldehyde, butadiene, methyl tertiary butyl ether, and ethanol were measured in vehicle-related high-end microenvironments (ME) under worst-case conditions plausibly simulating the >99th percentile of inhalation exposure concentrations in Atlanta (baseline gasoline), Chicago (ethanol-oxygenated gasoline), and Houston (methyl tertiary butyl either-oxygenated gasoline) during winter and summer seasons. High-end MSAT values as ratios of the corresponding measurements at nearby air monitoring stations exceeded the microenvironmental proximity factors used in regulatory exposure models, especially for refueling operations and MEs under reduced ventilation. MSAT concentrations were apportioned between exhaust and evaporative vehicle emissions in Houston where methyl tertiary butyl ether could be used as a vehicle emission tracer.

Concentrations of mobile source air pollutants in urban microenvironments.

Human exposures to criteria and hazardous air pollutants (HAPs) in urban areas vary greatly due to temporal-spatial variations in emissions, changing meteorology, varying proximity to sources, as well as due to building, vehicle, and other environmental characteristics that influence the amounts of ambient pollutants that penetrate or infiltrate into these microenvironments. Consequently, the exposure estimates derived from central-site ambient measurements are uncertain and tend to underestimate actual exposures. The Exposure Classification Project (ECP) was conducted to measure pollutant concentrations for common urban microenvironments (MEs) for use in evaluating the results of regulatory human exposure models.

Measurement of microenvironmental ozone concentrations in Durham, North Carolina, using a 2B Technologies 205 Federal Equivalent Method monitor and an interference-free 2B Technologies 211 monitor.

Unlabelled: During August and September of 2012, researchers conducted a microenvironmental (ME) monitoring study in Durham, North Carolina, using two 2B Technologies O3 monitors: a dual-beam model 205 Federal Equivalent Method (FEM) 254 nm photometer and a newly developed model 211 interference-free dual-beam photometer. The two monitors were mounted in a wheeled, fan-cooled suitcase together with a battery, a disposable N2O cartridge for the model 211 monitor and filtered sample lines. A scripted technician made paired O3 measurements in a variety of MEs within 2 miles of a fixed-site FEM O3 photometer at the Durham National GuardArmory.

A re-examination of ambient air ozone monitor interferences.

Attaining the National Ambient Air Quality Standard (NAAQS) for ozone (O3) could cost billions of dollars nationwide. Attainment of the NAAQS is judged on O3 measurements made by the Federal Reference Method (FRM), ethylene chemiluminescence, or a Federal Equivalent Method (FEM), predominantly ultraviolet (UV) absorption. Starting in the 1980s, FRM monitors were replaced by FEMs so that today virtually all monitoring in the United States uses the UV methodology.

Continuous monitoring of particle emissions during showering.

Particle formation from showering may be attributed to dissolved mineral aerosols remaining after evaporation of micron-sized satellite droplets produced by the showerhead or from splashing of larger shower water droplets on surfaces. Duplicate continuous particle monitors measured particle size distributions in a ventilated residential bathroom under various showering conditions, using a full-size mannequin in the shower to simulate splashing effects during showering. Particle mass concentrations were estimated from measured shower particle number densities and used to develop emission factors for inhalable particles.

Potential interference bias in ozone standard compliance monitoring.

The U.S. Environmental Protection Agency has established a federal reference method (FRM) for ozone (O3) and allowed for designation of federal equivalent methods (FEMs).

Frequency of open windows in motor vehicles under varying temperature conditions: a videotape survey in Central North Carolina during 2001.

Air pollution exposures in the motor vehicle cabin are significantly affected by air exchange rate, a function of vehicle speed, window position, vent status, fan speed, and air conditioning use. A pilot study conducted in Houston, Texas, during September 2000 demonstrated that useful information concerning the position of windows, sunroofs, and convertible tops as a function of temperature and vehicle speed could be obtained through the use of video recorders. To obtain similar data representing a wide range of temperature and traffic conditions, a follow-up study was conducted in and around Chapel Hill, North Carolina at five sites representing a central business district, an arterial road, a low-income commercial district, an interstate highway, and a rural road.

A pilot study using scripted ventilation conditions to identify key factors affecting indoor pollutant concentration and air exchange rate in a residence.

A pilot study was conducted using an occupied, single-family test house in Columbus, OH, to determine whether a script-based protocol could be used to obtain data useful in identifying the key factors affecting air-exchange rate (AER) and the relationship between indoor and outdoor concentrations of selected traffic-related air pollutants. The test script called for hourly changes to elements of the test house considered likely to influence air flow and AER, including the position (open or closed) of each window and door and the operation (on/off) of the furnace, air conditioner, and ceiling fans. The script was implemented over a 3-day period (January 30-February 1, 2002) during which technicians collected hourly-average data for AER, indoor, and outdoor air concentrations for six pollutants (benzene, formaldehyde (HCHO), polycyclic aromatic hydrocarbons (PAH), carbon monoxide (CO), nitric oxide (NO), and nitrogen oxides (NO(x))), and selected meteorological variables.

Determining the frequency of open windows in motor vehicles: a pilot study using a video camera in Houston, Texas during high temperature conditions.

Researchers have developed a variety of computer-based models to estimate population exposure to air pollution. These models typically estimate exposures by simulating the movement of specific population groups through defined microenvironments. Exposures in the motor vehicle microenvironment are significantly affected by air exchange rate, which in turn is affected by vehicle speed, window position, vent status, and air conditioning use.