Identify deficiencies that may impact IEQ and/or sources of odor concerns. Typically includes the following depending on the nature of concern, but not limited to:
- interview/questionnaire of concern individual(s)
- inspection above drop ceiling (condition of roof deck, pipe insulation, return air plenum)
- inspection of ventilation system (operation of variable air volume box and outdoor air dampers, check controls, measurements of carbon dioxide, temperature and relative humidity, sources near outdoor air intake, measure return and supply air volume, cleanliness of coils, liner and condensate pan)
- inspection of exterior
- inspection below drop ceiling (housekeeping, sink and floor drain traps, signs of past and present moisture concern via visual and/or moisture meter, mold growth, ensure connection of current and capping of abandoned sanitary vents, odorizers, excessive plants and fabric items, identify potential pathways, and measure volatile organic compounds, carbon monoxide, and lighting)
Date(s) of Assessment: January 26, 29, and 30, 2024
The Heating Ventilation and Air Conditioning (HVAC) Unit serving the area in question is Roof Top Unit-19 (RTU-19). The gas furnace within the unit uses a hot surface ignitor to ignite the natural gas in the furnace which then produces a flame (combustion). A fan moves the products of combustion (flue gases) through the heat exchanger, warming the heat exchanger section of the gas furnace. This heat (not the flue gas) is transferred to the supply air stream which provides warm air to the classrooms. The flue gases within the exchanger are then exhausted out of the unit through exhaust ports. The flue gases may contain Carbon Monoxide depending on the efficiency of combustion within the unit. The flue gases also contain carbon dioxide. The flue gases are not designed to mix with the warm air supplied to the classrooms.
January 26, 2024
The Office of the Environment collected various carbon monoxide readings within Room 69. The readings were collected in the general occupied areas and at each supply diffuser within the room. No carbon monoxide was detected at any of the sampling locations.
No odors of concern were identifed.
Given the unseasonable warm outdoor temperature (67.9 degrees Fahrenheit (F) at the time of sampling), it is likely that the heat was not operational at the time these measurements were taken.
January 29, 2024
The Office of the Environment arrived prior to student arrival to assess carbon monoxide conditions in RTU-19's zone. Outdoor temperatures were much cooler at this time (low 40's) therefore heating would have been required. Carbon monoxide samples were collected within Classroom 69 and the main pod area. No carbon monoxide was detected.
The Office of the Environment met a staff member from Building Maintenance at RTU-19. The individual indicated that the ignitor for the heat exchanger was not functioning. The system would introduce un-combusted natural gas to the hot surface ignitor, attempt to ignite three times, then "lock-out."
Building Maintenance had already replaced the hot surface ignitor prior to the meeting and was in the process of performing a combustion analysis of the heat exchanger (no concerns reported with the combustion analysis).
January 30, 3024
The Office of the Environment arrived mid-day (approximately 1PM) and collected additional carbon monoxide readings from Room 69 and the common area. No carbon monoxide was detected.
Carbon Dioxide
Carbon dioxide is also a by-product of the combustion process. A data logger was placed on January 26 and collected on February 2, 2024. Elevated carbon dioxide readings could be a potential indicator that flue gases are being entrained back into the outdoor air intake of the HVAC unit. Carbon dioxide readings were typical of HCPSS classrooms suggesting that flue gases are not negatively impacting air quality in occupied spaces.
It should also be noted that a lack of outside air introduced through the ventilation system could be associated with the general health symptoms reported. Carbon dioxide is an indicator compound for assessing sufficient delivery of outside air. The carbon dioxide readings were not elevated and suggest sufficient outside air is being delivered to the space. The outside air dampers for the unit were assessed and were open as designed.
Conclusion
No carbon monoxide was detected in the space during any of the measurements. Carbon dioxide readings were typical of HCPSS classrooms. Expected carbon dioxide readings and no carbon monoxide detections suggest that flue gases are not negatively impacting air quality in occupied spaces.
The Office of the Environment had not encountered an odor during the visits, however a staff member reported the intermittent odor as similar to propane . The intermittent odor sensed by occupants was likely due to the system introducing natural gas in an attempt to ignite. When no ignition occurred, a small amount of natural gas could have been entrained into the air stream through the outdoor air intake for the unit. The ignitor was replaced by Building Maintenance on January 26, 2024.