D.T. Grimsrud

Ventilation rates and health: multidisciplinary review of the scientific literature

UNLABELLED The scientific literature through 2005 on the effects of ventilation rates on health in indoor environments has been reviewed by a multidisciplinary group. The group judged 27 papers published in peer-reviewed scientific journals as providing sufficient information on both ventilation rates and health effects to inform the relationship. Consistency was found across multiple investigations and different epidemiologic designs for different populations. Multiple health endpoints show similar relationships with ventilation rate. There is biological plausibility for an association of health outcomes with ventilation rates, although the literature does not provide clear evidence on particular agent(s) for the effects. Higher ventilation rates in offices, up to about 25 l/s per person, are associated with reduced prevalence of sick building syndrome (SBS) symptoms. The limited available data suggest that inflammation, respiratory infections, asthma symptoms and short-term sick leave increase with lower ventilation rates. Home ventilation rates above 0.5 air changes per hour (h(-1)) have been associated with a reduced risk of allergic manifestations among children in a Nordic climate. The need remains for more studies of the relationship between ventilation rates and health, especially in diverse climates, in locations with polluted outdoor air and in buildings other than offices. PRACTICAL IMPLICATIONS Ventilation with outdoor air plays an important role influencing human exposures to indoor pollutants. This review and assessment indicates that increasing ventilation rates above currently adopted standards and guidelines should result in reduced prevalence of negative health outcomes. Building operators and designers should avoid low ventilation rates unless alternative effective measures, such as source control or air cleaning, are employed to limit indoor pollutant levels.

Control of Respirable Particles in Indoor Air with Portable Air Cleaners

Abstract Eleven portable air cleaning devices have been evaluated for control of indoor concentrations of respirable particles using in situ chamber decay tests. Following injection of cigarette smoke in a room-size chamber, decay rates for particle concentrations were obtained for total number concentration and for number concentration by particle size with and without air cleaner operation. The size distribution of the tobacco smoke particles was log normal with a count median diameter of 0.15 μm and a geometric standard deviation of 2.0. Without air cleaner operation, the natural mass-averaged surface deposition rate of particles was observed to be 0.1 h −1 . Air cleaning rates for particles were found to be negligible for several small panel-filter devices, a residential-sized ion-generator, and a pair of mixing fans. Electrostatic precipitators and extended surface filters removed particles at substantial rates, and a HEPA-type filter was most efficient air cleaner studied.

Radon transport into a detached one-story house with a basement

We describe the results of a five-month study during which 222Rn (radon) concentration, air- exchange (or ventilation) rate, and weather and radon source parameters were continuously monitored in a house near Chicago, with a view to accounting for the radon entry rate. The results suggest that the basement sump and perimeter drain-tile system played an important role in influencing the radon entry rate and that pressure-driven flow was more important than diffusion as a mechanism for radon entry. For the first 15 weeks of the study period the mean indoor radon concentration and air-exchange rate were 2.6pCil−1 (96 Bq m−3) and 0.22h−1, respectively; both parameters varied over a wide range. Radon concentration measured at the sump cover varied bimodally between 0 and 10 pCil−1 (0–400 Bqm−3) and 300–700 pCil−1 (10,000–30,000 Bq m−3). These two modes corresponded well to periods of low and high indoor radon concentration; average indoor concentrations for these periods were 1.5 and 6.5 pCil−1 (55 and 240 Bq m−3), respectively. For data sorted into two groups according to radon activity at the sump, the indoor radon concentration showed little dependence on air-exchange rate. This result is accounted for by a model in which the radon entry rate, determined by mass balance, has two components—one diffusive, the other a pressure-driven flow component which is presumed to be proportional to the air-exchange rate. In fitting this model to the data we found that (1) the flow component dominated the diffusive component for periods of both high and low activity at the sump and (2) the magnitude of the diffusive component agreed well with the expected contributions of radon emanating from concrete and soil and diffusing into the house. To account for the flow component, we hypothesize that pressure drives air carrying a high concentration of radon generated in the soil, either through the bulk of the soil or along the outside of the basement walls, then into the basement through cracks and openings. During the final six weeks of the study, measurements were made with the water level in the sump maintained first below, then above the entrance of the pipe connected to the perimeter drain tile system. Average indoor radon concentrations during these two periods were 10.6 and 3.5 pCil−1 (390 and 130 Bq m−3), respectively. The relatively high latter value compared with the mean for the first 15 weeks, combined with the observation of intervals of high airborne alpha activity at the sump during this period, suggest that the level of water in the sump does not, by itself, account for the variation in alpha activity at the sump that we had previously observed. Fireplace operation substantially increased the air-exchange rate, but had only a small effect on indoor radon concentration, providing corroborative evidence that pressure-driven flow is an important mechanism for radon entry into this house.

Indoor air pollution due to emissions from wood-burning stoves

Four wood-burning stoves, three airtight and one non-airtight, were operated in a single-floor 236-m/sup 3/ residence and tested for indoor pollutant emissions. Results showed the airtight stoves emitted minor amounts of carbon monoxide and respirable suspended particles during door-opening operations, while the nonairtight stove continuously injected pollutants indoors under certain operating conditions. During airtight stove operation, carbon monoxide levels reached a maximum of 4 ppm, while average total suspended particulate levels ranged from 24 to 71 ..mu..g/m/sup 3/. During normal nonairtight stove operation, carbon monoxide levels reached a maximum of 8 ppm, while total suspended particulate levels ranged from 30 to 650/sup +/g/m/sup 3/. Outdoor carbon monoxide levels were 1.1 ppm or less, and outdoor particulate levels ranged from 7 to 31 ..mu..g/m/sup 3/. Five polycyclic aromatic hydrocarbons, including benzo(a)pyrene, were measured in the collected particulate samples, and the results are reported. Source strengths for carbon monoxide, total suspended particles, and five polycyclic aromatic hydrocarbons are reported. 26 references, 4 figures, 5 tables.

Change in indoor particle levels after a smoking ban in Minnesota bars and restaurants.

BACKGROUND Smoking bans in bars and restaurants have been shown to improve worker health and reduce hospital admissions for acute myocardial infarction. Several studies have also reported improved indoor air quality, although these studies generally used single visits before and after a ban for a convenience sample of venues. PURPOSE The primary objective of this study was to provide detailed time-of-day and day-of-week secondhand smoke-exposure data for representative bars and restaurants in Minnesota. METHODS This study improved on previous approaches by using a statistically representative sample of three venue types (drinking places, limited-service restaurants, and full-service restaurants), conducting repeat visits to the same venue prior to the ban, and matching the day of week and time of day for the before- and after-ban monitoring. The repeat visits included laser photometer fine particulate (PM₂.₅) concentration measurements, lit cigarette counts, and customer counts for 19 drinking places, eight limited-service restaurants, and 35 full-service restaurants in the Minneapolis/St. Paul metropolitan area. The more rigorous design of this study provides improved confidence in the findings and reduces the likelihood of systematic bias. RESULTS The median reduction in PM₂.₅ was greater than 95% for all three venue types. Examination of data from repeated visits shows that making only one pre-ban visit to each venue would greatly increase the range of computed percentage reductions and lower the statistical power of pre-post tests. Variations in PM₂.₅ concentrations were found based on time of day and day of week when monitoring occurred. CONCLUSIONS These comprehensive measurements confirm that smoking bans provide significant reductions in SHS constituents, protecting customers and workers from PM₂.₅ in bars and restaurants.

Characterizing the occurrence, sources, and variability of radon in pacific northwest homes

A compilation of data from earlier studies of 172 homes in the Pacific Northwest indicated that approximately 65 percent of the 46 homes tested in the Spokane River Valley/Rathdrum Prairie region of eastern Washington/northern Idaho had heating season indoor radon (222Rn) concentrations above the U. S. EPA guideline of 148 Bq m-3 (4 pCi L-1). A subset of 35 homes was selected for additional study. The primary source of indoor radon in the Spokane River Valley/Rathdrum Prairie was pressure-driven flow of soil gas containing moderate radon concentrations (geometric mean concentration of 16,000 Bq m-3) from the highly permeable soils (geometric mean permeability of 5 x 10(-11) m2) surrounding the house substructures. Estimated soil gas entry rates ranged from 0.4 to 39 m3h-1 and 1 percent to 21 percent of total building air infiltration. Radon from other sources, including domestic water supplies and building materials was negligible. In high radon homes, winter indoor levels averaged 13 times higher than summer concentrations, while in low radon homes winter levels averaged only 2.5 times higher. Short-term variations in indoor radon were observed to be dependent upon indoor-outdoor temperature differences, wind speed, and operation of forced-air furnace fans. Forced-air furnace operation, along with leaky return ducts and plenums, and openings between the substructure and upper floors enhanced mixing of radon-laden substructure air throughout the rest of the building.

Temperature- and wind-induced air flow patterns in a staircase. Computer modelling and experimental verification

Abstract The typical infiltration load for a residential building has been found to range from one-third to one-half of the total space conditioning load. However, most infiltration measurements have been made on single-family houses. Information about the role of infiltration in the energy consumption of large buildings is limited. Furthermore, the prediction of infiltration rates in high-rise buildings is a complex problem. The forces that drive this flow result from the superposition of wind pressure on the faces of the building and the stack effect across the height of the building. Infiltration models have shown the latter effect to be significant in single-family residences, particular in colder climates and, consequently, the stack effect is even greater in high-rise buildings. For this work, we performed tracer gas and fan pressurization measurements on a 30 m tall University of California dormitory in order to determine the importance of both wind and stack effect upon infiltration. Measured pressure and tracer gas distributions were compared with those from a predictive infiltration computer model for high-rise buildings. To study the influence of the air flow pattern around the building, this model uses various wind velocity profiles characteristic of urban areas and different sets of surface pressure coefficients derived from wind tunnel experiments.

Indoor air pollution and inter-room pollutant transport due to unvented kerosene-fired space heaters

Abstract Two kerosene-fired space heaters, one white-flame convective and one blue-flame radiant, were operated in the master bedroom and living room of an unoccupied house (elevation: 1800 m) under several simulated use conditions. Tests were conducted in the master bedroom with the bedroom door and bedroom window open and closed. The heaters were operated until an 8 °C temperature rise was achieved in the room. Increases in bedroom concentrations of CO, CO 2 , NO, NO 2 , and O 2 are reported. The increases in CO 2 levels ranged from 2440 to 5440 mL/m 3 (ppm) while the increases in NO 2 levels ranged from 0.12 to 0.60 mL/m 3 (ppm). The NO 2 emission rate from the convective heater was reduced at the high altitude location as compared with previous emission rate measurements conducted near sea level with the same heater. In addition, inter-room pollutant transport rates are reported for bedroom tests conducted with the window closed. While inter-room pollutant transport rates were less than 10 m 3 with the bedroom door closed (opening area less than 100 cm 2 ), they ranged from 16 m 3 /h to 53 m 3 /h with the bedroom door open 2.5 cm (opening = 520 cm 2 ), and ranged from 190 to 3400 m 3 /h with the door fully open (opening area = 15,000 cm 2 ). Continuous emission rate data are reported for tests conducted with the heater in the living room.

Effectiveness of radon control techniques in fifteen homes

Radon control systems were installed and evaluated in fourteen homes in the Spokane River Valley/Rathdrum Prairie and in one home in Vancouver, Washington. Because of local soil conditions, subsurface ventilation (SSV) by pressurization was always more effective in these houses than SSV by depressurization in reducing indoor radon levels to below guidelines. Basement overpressurization was successfully applied in five houses with airtight basements where practical-sized fans could develop an overpressure of 1 to 3 Pascals. Crawlspace ventilation was more effective than crawlspace isolation in reducing radon entry from the crawlspace, but had to be used in conjunction with other mitigation techniques, since the houses also had basements. Indoor radon concentrations in two houses with air-to-air heat exchangers (AAHX) were reduced to levels inversely dependent on the new total ventilation rates and were lowered even further in one house where the air distribution system was modified. Sealing penetrations in the below-grade surfaces of substructures was relatively ineffective in controlling radon. Operation of the radon control systems (except for the AAHXs) made no measureable change in ventilation rates or indoor concentrations of other measured pollutants. Installation costs by treated floor area ranged from approximately

Assessment of residential exhaust-air heat pump applications in the United States

4/m2 for sealing to