Concern: Oakland Mills High School: September 3rd, 2021 (CXOMHS20210001EC)

Room 809
Date of IEQ Report Form
Date of Report
My daughter and her friend complain of headaches each day they have been in biology. I checked the IEQ for OMHS and noted that on July 20 this was reported: 808 and 809 - Significant relative humidity mold on wooden cabinets in both rooms (served by the same air handling unit). See IEQ Concern CXOMHS20210001C9. Has this issue been addressed? I am concerned that she complains of headaches upon entering a room found to have mold just two months ago.
IEQ Investigation Process

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 of Assessment: September 8 and 10, 2021

Historical Information

Mold growth was previously identified in the space on July 20, 2021. 

Building Maintenance (HVAC) assessed the unit (Roof Top Unit (RTU) - 8) and attempted to slow the fan speed within the unit to bring in less humid outdoor air in to the space.

A board-approved restoration contractor cleaned/disinfected surfaces within the zone served by RTU-8 (Rooms 808 and 809).

Information regarding the previous assessment can be found in association with IEQ Concern #CXOMHS20210001C9.

Recent Assessment

The Office of the Environment revisited the space and noted "new" mold growth on some wooden surfaces within room 809.

The Office of the Environment spoke with Building Maintenance (HVAC) about the possible cause and it was reported that the unit may be oversized. An oversized unit can "short-cycle" causing the unit to turn on/off. As a general rule, when operating in the cooling mode, an HVAC system needs to have continuous "on" times to provide proper dehumidification. 

Additionally, the systems have been operating for additional run-times (2-hours before and after school). The additional run-times associated with this type of HVAC system (constant volume) can cause humidity/mold issues during certain weather conditions (humid), especially when the area is unoccupied (reduced heat load). Running the units for an additional four hours a day (two hours before and after school) is being conducted system-wide as it is a COVID-19 mitigation measure recommended by the Center for Disease Control (CDC).

Building Maintenance (HVAC) reported that this type of HVAC system is located elsewhere in the school and includes the Science Wing (RTU-8, RTU-9, RTU-10, and RTU-11). Each zone includes two classrooms.

The Office of the Environment assessed the areas served by the above referenced HVAC units and identified mold growth in the following locations: 802, 804, 805, and 809.

Building Maintenance (HVAC) is operating HVAC units throughout the school-system with the outside air dampers open during summer as a COVID-19 mitigation measure. Operating this equipment with the dampers open during summer operations is not standard practice for HCPSS, and likely contributed to elevated humidity and subsequent mold growth this summer (building un-occupied).

As it relates to the building being fully occupied - the Office of the Environment believes the additional run-times coupled with the units oversizing and system type (constant volume) was the cause of the mold growth.

It should be noted, that the Office of the Environment is not aware of this having ever occurred in these areas in the past, therefore the units being reported as oversized does not appear to present a significant issue during "normal" (non-pandemic) circumstances.

Corrective Actions
September 10th, 2021

A board-approved restoration contractor cleaned/disinfected rooms 802, 804, 805, 808, and 809 on September 10, 2021. Additionally, portable dehumidification units were delivered to each of the classrooms served by RTU-8 through RTU-11. The units will remain until weather permitting (October).

On September 14, 2021, the remaining classrooms served by RTU-8 through RTU-11 were cleaned/disinfected by a board-approved restoration contractor as a precaution.

During the summer (not occupied by significant students/staff), the Office of the Environment recommends these units be operated similar to "pre-pandemic" summer operations (outside air dampers closed, 2-hour afternoon run-time, etc.) unless requested by a custodian (no single unit should run for more than one consecutive week).

During occupied times (cooling-season), if Building Maintenance is to operate these units for additional run-times next spring/summer, portable dehumidification units should be provided to each classroom in the zones associated with RTU-8 through 11.

If dehumidifiers cannot be provided, the units should not be operated for additional run-times. Note, this recommendation recognizes that portable air purifiers have been added to HCPSS classrooms as an additional COVID-19 mitigation strategy. 

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