Spatial and temporal variations in indoor environmental conditions, human occupancy, and operational characteristics in a new hospital building.

The dynamics of indoor environmental conditions, human occupancy, and operational characteristics of buildings influence human comfort and indoor environmental quality, including the survival and progression of microbial communities. A suite of continuous, long-term environmental and operational parameters were measured in ten patient rooms and two nurse stations in a new hospital building in Chicago, IL to characterize the indoor environment in which microbial samples were taken for the Hospital Microbiome Project. Measurements included environmental conditions (indoor dry-bulb temperature, relative humidity, humidity ratio, and illuminance) in the patient rooms and nurse stations; differential pressure between the patient rooms and hallways; surrogate measures for human occupancy and activity in the patient rooms using both indoor air CO2 concentrations and infrared doorway beam-break counters; and outdoor air fractions in the heating, ventilating, and air-conditioning systems serving the sampled spaces. Measurements were made at 5-minute intervals over consecutive days for nearly one year, providing a total of ∼8×106 data points. Indoor temperature, illuminance, and human occupancy/activity were all weakly correlated between rooms, while relative humidity, humidity ratio, and outdoor air fractions showed strong temporal (seasonal) patterns and strong spatial correlations between rooms. Differential pressure measurements confirmed that all patient rooms were operated at neutral pressure. The patient rooms averaged about 100 combined entrances and exits per day, which suggests they were relatively lightly occupied compared to higher traffic environments (e.g., retail buildings) and more similar to lower traffic office environments. There were also clear differences in several environmental parameters before and after the hospital was occupied with patients and staff. Characterizing and understanding factors that influence these building dynamics is vital for hospital environments, where they can impact patient health and the survival and spread of healthcare associated infections

BUILDING SCIENCE MEASUREMENTS FOR THE HOSPITAL MICROBIOME PROJECT

The Hospital Microbiome Project was designed to study the progression of microbial communities present inside and nearby patient rooms in a new hospital pavilion recently built at the University of Chicago, both before the hospital was occupied and for nearly one year after introduction of patients and hospital staff. A suite of building science measurements, which is the focus of this work, was also designed and implemented to provide potentially meaningful data on several building environmental and operational parameters that may have influenced microbial communities inside the hospital. The building science measurement plan included characterizations of indoor air temperature, relative humidity (RH), absolute humidity, light levels, outdoor air fractions in the HVAC systems, room pressurization, and human occupancy using both beam break counters and CO2 concentrations in the 10 patient rooms and 2 nurse stations. Each parameter was measured at 5-minute intervals over the span of nearly one year, which resulted in more than 8 million collected data points. Air temperatures varied more than expected for such a typically tightly controlled environment, with surprisingly low correlations between rooms. RH and absolute humidity were highly correlated between patient rooms, indicating a strong effect from the HVAC system and little effect from occupants. Humidity was more tightly controlled during summer and winter months when the weather was most extreme in Chicago. Light intensity levels were not found to be very different between rooms and floors (which received similar solar exposure), but large seasonal patterns were apparent. CO2 was moderately correlated with non-directional IR beam-break counts at times, but not consistently. IR beam-break counters revealed large variations in patient room occupancy xv patterns throughout the study. In the HVAC systems serving each floor, outdoor air (OA) fractions were successfully calculated using CO2 concentrations measured in the outdoor air intake, recirculation air, and supply air, albeit only after periodic calibrations with data from the building automation system. OA fractions also showed distinct patterns of economizer usage with outdoor temperatures. Ultimately, this large suite of building science data will be used alongside microbial diversity data to explore correlations between indoor microbiology and the built environment.M.S. in Environmental Engineering, May 201

Spatial and Temporal Variations in Indoor Environmental Conditions, Human Occupancy, and Operational Characteristics in a New Hospital Building

The dynamics of indoor environmental conditions, human occupancy, and operational characteristics of buildings influence human comfort and indoor environmental quality, including the survival and progression of microbial communities. A suite of continuous, long-term environmental and operational parameters were measured in ten patient rooms and two nurse stations in a new hospital building in Chicago, IL to characterize the indoor environment in which microbial samples were taken for the Hospital Microbiome Project. Measurements included environmental conditions (indoor dry-bulb temperature, relative humidity, humidity ratio, and illuminance) in the patient rooms and nurse stations; differential pressure between the patient rooms and hallways; surrogate measures for human occupancy and activity in the patient rooms using both indoor air CO2 concentrations and infrared doorway beam-break counters; and outdoor air fractions in the heating, ventilating, and air-conditioning systems serving the sampled spaces. Measurements were made at 5-minute intervals over consecutive days for nearly one year, providing a total of ∼8×106 data points. Indoor temperature, illuminance, and human occupancy/activity were all weakly correlated between rooms, while relative humidity, humidity ratio, and outdoor air fractions showed strong temporal (seasonal) patterns and strong spatial correlations between rooms. Differential pressure measurements confirmed that all patient rooms were operated at neutral pressure. The patient rooms averaged about 100 combined entrances and exits per day, which suggests they were relatively lightly occupied compared to higher traffic environments (e.g., retail buildings) and more similar to lower traffic office environments. There were also clear differences in several environmental parameters before and after the hospital was occupied with patients and staff. Characterizing and understanding factors that influence these building dynamics is vital for hospital environments, where they can impact patient health and the survival and spread of healthcare associated infections.</p

Variations between nighttime and daytime periods for hourly average air temperature, humidity ratio, illuminance, room CO₂ concentration, and outdoor air fraction, as well as hourly total IR beam-breaks.

<p>Box plots display median values in the center, bounded by the interquartile range in gray and extreme values at top and bottom. Figures exclude outlier values for clarity.</p

Distribution dot plots for four measured environmental conditions in the hospital: (a) hourly average air temperature, (b) hourly average relative humidity, (c) hourly average humidity ratio, and (d) daily average illuminance levels.

<p>Rooms 101–105 are on the 9^th floor; rooms 201–205 are on the 10^th floor. Room 100 and 200 are the nurse station locations on the 9^th and 10^th floor, respectively. The horizontal black bar represents the median hourly values (only daily averages are provided in part (d) for better graphical clarity).</p

Weekly averages of environmental conditions in the patient rooms and nurse stations measured over the duration of the project: (a) temperature, (b) relative humidity, (c) humidity ratio, and (d) illuminance.

<p>Rooms 101–105 are on the 9^th floor; rooms 201–205 are on the 10^th floor. Room 100 and 200 are the nurse station locations on the 9^th and 10^th floor, respectively. Weeks are counted from the week of hospital opening (i.e., week 0). White areas represent missing values. Values along the x-axes correspond to room identification numbers. Examples time series data at 5-min intervals for one day are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118207#pone.0118207.s005" target="_blank">S5 Fig.</a></p

Typical patient room showing locations of built environment sensors and microbial sampling sites.

<p>Sketch of a typical patient room in the hospital. Green shaded areas show microbiological sampling sites; areas circled in blue show locations of the building science measurements sites used herein. The nurse stations, although not pictured, were centrally located to the right of the figure (in the gray area).</p

Variations between floors for hourly average air temperature, relative humidity, humidity ratio, illuminance, and room CO₂ concentration, as well as hourly total IR beam-breaks.

<p>Box plots display median values in the center, bounded by the interquartile range in gray and extreme values at top and bottom. Figures exclude outlier values for clarity.</p

Surrogates for daily human occupancy and activity: (a) daily total IR bream-break counts and (b) daily average room-source CO₂ concentrations.

<p>Rooms 101–105 are on the 9^th floor; rooms 201–205 are on the 10^th floor. The horizontal black bar represents the median daily values</p