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Building Assessment Survey and Evaluation (BASE) Study
Methodology
Between 1994 and 1998, data and samples were collected in each of 100 office buildings using a Standardized Protocol (PDF, 311 pp, 1.5MB) over a one-week period (click here to see the week schedule chart) during either the summer or winter season. The protocol provides detailed information on the procedures used for conducting the building investigations and occupant surveys in each of the BASE buildings. Supporting information, a set of checklists developed to consistently collect information on the whole building and the study area(s), and a sample questionnaire are provided in the appendices of the protocol.
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There were seven basic activities performed for each of the buildings:
- Select and Recruit Buildings
- Initial Visit to Eligible Buildings
- Create a Study Team
- Select Study Area(s) and Monitoring Locations
- Monitor Study Area(s)
- Survey Occupants of Study Area(s)
- Validation of data as specified in the Quality Assurance Project Plan (PDF, 32 pp, 77KB)
Buildings selected and recruited for monitoring represent both public and commercial office buildings in the United States. The buildings were randomly selected within the chosen city without regard to indoor air quality concerns except that buildings with highly publicized indoor air quality concerns were excluded. Both complaint and non-complaint buildings may be included in the study. A detailed discussion of the BASE building selection process is contained in the report Summary and Analysis Report of the BASE Study Building Selection Process (PDF, 112 pp, 1.34MB).
It was important that the suitability of a building be established well ahead of conducting the monitoring. Therefore, if a building met the eligibility requirements and the building manager/owner was interested in participating in the study, an on-site preliminary visit (PV) was scheduled as soon as possible after the building was selected and recruited into the study. A schematic flowchart of the BASE Building Selection Process (PDF, 3 pp, 133KB) is available here.
Initial Visit to Eligible Buildings
Initial visits for eligible buildings in a given city were conducted over the course of a week. The objectives of the visits were to verify the suitability of the building for the study, to identify potential study areas for monitoring, to select one or more study areas for monitoring, and to collect information that could be used to select monitoring locations within the study area(s). Information on the whole building, including space use, occupancy, climate and site, building and HVAC equipment, building envelope, and potential pollutant sources were collected during the initial visit using standardized checklists available in the appendices of the Standardized Protocol (PDF, 311 pp, 1.5MB). Based on the initial visit, a building was considered suitable for inclusion in the monitoring study if it has at least one space that met the BASE criteria for designating a building space as a study area(s), see Criteria for Designating a BASE Building Space as a Study Area) (PDF, 1 page, 10KB). The final test buildings were randomly selected from all buildings found to be eligible within the chosen test city.
A four to five-person study team was formed for each building. Each study team was responsible for all data collection, data reduction, and data entry activities associated with individual buildings or a group of buildings monitored as part of the BASE study. Each study team designated a study team leader, field team leader, analysis team leader, sample custodian, survey administrator, data management specialist, and QA officer prior to field monitoring activities. The same individual could be designated to perform several of these functions. However, the QA officer was independent of the study team technical staff and routine sampling and analysis activities to avoid the potential for conflict of interest. EPA determined a List of Team Responsibilities and Experience Requirements (PDF, 4 pp, 14KB) necessary to ensure program success.
Select Study Area(s) and Monitoring Locations
A “test space” (also referred to as the study space) was selected in each building using established criteria, see Criteria for Designating a BASE Building Space as a Study Area (PDF, 1 page, 10KB).
Potential study areas within each building were defined and then one or more study area(s) were randomly selected for more extensive evaluation. Within the selected study area(s) three fixed indoor sites and one outdoor site as close as possible to the fresh air intake of the primary air handling unit (AHU) serving the study area, were selected for taking physical and chemical measurements based upon a set procedure.
On the Monday morning of the field week monitoring locations were randomly selected using a set procedure. Two types of monitoring locations, fixed and mobile (see Glossary), were established in each building based on established guidelines. Fixed indoor (click here to see image) monitoring locations and a fixed outdoor (click here to see image) monitoring location were selected during the initial field visit. The outdoor site was selected to be as close as possible to the fresh air intake of the primary AHU serving the study space. Five mobile indoor monitoring locations were also established in each study area.
Monitoring was performed in the study area(s) during a one-week period to generate data on heating, ventilation, and air-conditioning (HVAC) system operation, environmental pollutants, and comfort factors. Checklists were used to consistently collect information on the whole building, the HVAC, and the study area(s). These checklists are available in appendices of the Standardized Protocol (PDF, 311 pp, 1.5MB).
- Whole Building and Study Area(s) Characterization
- Environmental Monitoring
- HVAC Characterization
- Quality Assurance/Quality Control
Whole Building and Study Area(s) Characterization
Information on the whole building was collected during the initial visit to the building. During the field test week, the field team leader reviewed and verified the information collected previously and recorded any changes that may have occurred since the site visit. Information on the study area(s) and specific sources were collected early in the week of measurements at the building.
Environmental monitoring included measurements for both comfort factors and environmental pollutants. Monitoring was performed with both real-time and integrated measurement methods (see Glossary) at the selected fixed and mobile sites. A listing of core parameters and sample collection methods used during the BASE study are listed below.
| Core Parameters and Sample Collection Methods | |
| Parameter | Sampling Method/Device |
| Real-Time Monitors | |
| Air Temperature (Dry Bulb) | Sensor |
| Relative Humidity | Sensor |
| CO2 | Monitor/Pump |
| CO | Monitor/Passive Diffusion or Pump |
| Sound Level | Sensor (microphone) |
| Illuminance | Sensor (light) |
| Integrated Samples | |
| Inhalable Particles (PM2.5) | Pump/size selective impactor, filter |
| Inhalable Particles (PM10) | Pump/size selective impactor, filter |
| Volatile Organic Compounds | Pump, Multisorbent cartridge and SUMMA® canister |
| Formaldehyde | Pump, DNPH cartridge |
| Bioaerosols | Pump/size selective impactor, agar media |
| Radon | Passive diffusion charcoal canister |
| Other Samples | |
| Bulk Biologicals a. | Sterile disposable pipettes, sterile sampling bottles, sample collection bags |
| HVAC Measurements | |
| Supply/Return Airflow Rate | Duct traverse/pitot tube b. |
| Supply/Return Air Temperature | Sensor |
| Supply/Return Air Humidity | Sensor |
| Percent Outdoor Air Intake - Based on Outdoor, Supply, Return Air Carbon Dioxide Levels | CO2 Monitor |
| Outdoor Air Intake Rate | Duct traverse/pitot tube b. |
| Exhaust Fan Airflow Rate | Flow capture hood, duct travers/pitot tube b. |
| Supply Diffuser Airflow Rate | Flow capture hood |
| Supply Diffuser Temperature | Sensor |
| Supply Diffuser Relative Humidity | Sensor |
| Supply Diffuser Carbon Dioxide | Sensor |
| Notes:
CO2 - Carbon Dioxide a. - Bulk samples from obviously contaminated sources (i.e., drip pans, ducts) were also collected for determination of bacteria and fungi. b. - May be performed with pitot tube, hot-wire anemometer, or comparable sensor. |
|
Twice daily the study team recorded observations related to odors, noise, housekeeping, and pollutant sources using a standardized checklist available in Appendix D of the Standardized Protocol (PDF, 311 pp, 1.5MB).
Core HVAC measurement parameters for each AHU that serves the study area(s) in mechanically ventilated buildings included direct volumetric measurements of airflow quantities (e.g., outdoor air intake rate, supply airflow), where possible,; and carbon dioxide (CO2) measurements in HVAC air streams to estimate the percentage of outdoor air relative to total supply air flow, where possible. Temperature and the relative humidity in the HVAC air streams were also measured. Measurements were also made at the air supply air diffusers located within the study areas, including air flows, temperatures, the relative humidity, and carbon monoxide levels.
In naturally ventilated buildings, the core measurement parameters included:
- continuous carbon dioxide measurements,
- measurements of exhaust fan airflow rate, and
- the twice-daily check of exhaust fan operation.
Quality Assurance/Quality Control
In addition to the field samples, various quality control (QC) samples were collected and analyzed during the study. The study team collected field samples and blanks. In addition to these samples, laboratory blanks and controls were prepared for each building by the analytical laboratory. These samples were to be analyzed if contamination or poor recovery was found on the field blanks. At each building, one field blank and one duplicate sample for each type of integrated sample were analyzed. More information on the procedures used to ensure consistent collection and reporting of quality data is available:
- the Quality Assurance Project Plan (QAPjP) (PDF, 32 pp, 77KB),
- the Standardized Protocol (PDF, 311 pp, 1.5MB), and
- the Field Standard Operating Procedures (SOPs).
In addition, a detailed discussion of the accuracy and precision of the data can be found in the Precision and Accuracy of Environmental Measurements for the Buildings Assessment Survey and Evaluation Program (PDF, 76 pp, 220KB).
Survey Occupants in Study Area(s)
Occupants in the study area(s) were surveyed on perceived IAQ and health symptoms using a self-administered questionnaire available in Appendix F of the Standardized Protocol (PDF, 311 pp, 1.5MB) on Thursday of the week of field monitoring. To help ensure that environmental monitoring and survey data would be applicable to the same group of people, the questionnaire was administered to full-time individuals (20 or more hours per week) whose primary workstation is in the study area(s).
Although the survey was conducted using a self-administered questionnaire, one member of the field team was designated as a survey administrator. The survey administrator’s responsibility was to enlist occupant participation, provide the elements of informed consent, distribute and collect the questionnaire, ensure questionnaire confidentiality, and make every attempt to collect data from all eligible occupants using specified procedures.