Building Assessment Survey and Evaluation (BASE) Study
Between 1994 and 1998, data and samples were collected in each of 100 office buildings using a Standardized Protocol (PDF) (311 pp, 1.5 M, About PDF) over a one-week period (see the Field Data Collection Activities Table below) 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 areas, and a sample questionnaire are provided in the appendices of the protocol.
Overview of Field Data Collection Activities During Study Week
|Initial Visit||As soon as possible after building is selected|
|Study area selection||During initial visit|
|Selection of monitoring locations within study area||Monday|
|Study area verification||Monday|
|Equipment preparation, setup, and calibration||Monday and Tuesday|
|Supply air and diffuser flow measurements||Tuesday|
|Building and study area characterization||Tuesday to Thursday|
|Measurement of environmental pollutants and comfort parameters||Tuesday to Thursday|
|HVAC measurements||Monday to Thursday|
|Field data check for completeness and validation||Thursday and Friday|
|Equipment take down, packing, and shipment||Thursday and Friday|
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 Areas and Monitoring Locations
- Monitor Study Areas
- Survey Occupants of Study Areas
- Validation of data as specified in the Quality Assurance Project Plan (PDF) (32 pp, 77 K)
Select and Recruit Buildings
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, 1.34 M).
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. See the schematic flowchart of the BASE Building Selection Process (PDF) (3 pp, 133 K).
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 areas. 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. 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 areas, see the table below. The final test buildings were randomly selected from all buildings found to be eligible within the chosen test city.
Table 1: Criteria for Designating a BASE Building Space as Study Areas
|Number of Occupants||25 occupants who work for 20 or more hours/week and are accessible to questionnaire||50 to 60 occupants who work for 20 or more hours/week and are accessible to questionnaire|
|Air Supply||Provided by no more than two air handling units||Provided by one air handling unit|
|Test Space||Totally contained in a maximum of three floors||Totally contained on one floor|
|Test Area||-||Not to exceed 20,000 square feet *|
|* Can be larger, however, deviation should be documented.|
Create a Study Team
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 necessary to ensure program success.
U.S. EPA BASE Study: Responsibilities and Qualifications for Study Team Members
|Study Team Leader||Project Management|
|Field Team Leader||Manage field management activities||
|Senior Field Technician||Sample collection and field monitoring; collection of information on HVAC systems and performance of core HVAC measurements||
|Field Technicians||Perform sample collection and monitoring||
|Analysis Team Leader||Manage data processing and analysis task||
|Analysis Technicians||Process and verify data||
|Sample Custodian||Maintain inventory of all materials required for field sampling; transfer unexposed and exposed samplers between field and laboratories; maintain chain of custody for all samples, checklists, questionnaires, documentation forms, and data||
|Quality Assurance Officer||Provide QA review and documentation for field operations, sample analysis, data reduction, and reporting||
|Survey Administrator||Administer questionnaire to building occupants; collect questionnaires||
|Data Management Specialist||Manage research team's database||
Select Study Areas and Monitoring Locations
A test space, also referred to as the study space, was selected in each building using established criteria, see Table 1 above.
Potential study areas within each building were defined and then one or more study areas were randomly selected for more extensive evaluation. Within the selected study areas three fixed indoor sites and one outdoor site as close as possible to the fresh air intake of the primary air handling unit, or 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 the Glossary), were established in each building based on established guidelines. Fixed indoor monitoring locations and a fixed outdoor 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.
Monitor Study Areas
Monitoring was performed in the study areas during a one-week period to generate data on heating, ventilation, and air-conditioning, or HVAC, system operation, environmental pollutants, and comfort factors. Checklists were used to consistently collect information on the whole building, the HVAC, and the study areas. These checklists are available in appendices of the 2003 Standardized BASE Protocol (PDF) (311 pp, 1.5 M).
- Whole Building and Study Areas Characterization
- Environmental Monitoring
- HVAC Characterization
- Quality Assurance/Quality Control
Whole Building and Study Area 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 areas 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 the 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
|Air Temperature (Dry Bulb)||Sensor|
|CO||Monitor/Passive Diffusion or Pump|
|Sound Level||Sensor (microphone)|
|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|
|Bulk Biologicals a.||Sterile disposable pipettes, sterile sampling bottles, sample collection bags|
|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|
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 2003 Standardized BASE Protocol.
Core HVAC measurement parameters for each AHU that serves the study area in mechanically ventilated buildings included direct volumetric measurements of airflow quantities, such as 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, or 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:
- Quality Assurance Project Plan (QAPjP) (PDF) (32 pp, 77 K)
- 2003 Standardized BASE Protocols (PDF) (311 pp, 1.5 M)
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, 220 K).
Survey Occupants in Study Areas
Occupants in the study areas were surveyed on perceived IAQ and health symptoms using a self-administered questionnaire available in Appendix F of the Standardized Protocol 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 areas.
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.
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