At the request of Walter Parker, Director of Buildings and Grounds, Mansfield Public Schools, the Massachusetts Department of Public Health (MDPH), Bureau of Environmental Health (BEH) provided assistance and consultation regarding indoor air quality concerns at Jordan/Jackson Elementary School (JJES), 255 East Street, Mansfield, Massachusetts. The request was prompted by occupant complaints of respiratory symptoms.
On February 15, 2008, an initial visit to conduct an assessment was made to the JJES by Mike Feeney, Director, and Cory Holmes and James Tobin, Environmental Analysts in BEH’s Indoor Air Quality (IAQ) Program. BEH staff were accompanied by Mr. Parker during the assessment. Mr. Holmes and Mr. Tobin returned to JJES on February 26, 2008 to complete the assessment. It was reported that over February vacation, intensive cleaning of classrooms was conducted, particularly the surfaces and interiors of classroom unit ventilators.
The school is a two-story brick building that was built in 1991. The building contains general classrooms, small rooms for specialized instruction, a library, a kitchen, a cafeteria, a gymnasium, an auditorium, office space, music/band rooms, art rooms and multipurpose rooms. Windows are openable throughout the building. The school has initiated a carpet removal project that was reportedly about 85 percent complete at the time of the assessment. This project involves removing wall to wall carpet and installing a non-porous flooring material (e.g., tile).
Air tests for carbon monoxide, carbon dioxide, temperature and relative humidity were conducted with the TSI, Q-Trak, IAQ Monitor, Model 8551. Air tests for airborne particle matter with a diameter less than 2.5 micrometers were taken with the TSI, DUSTTRAK™ Aerosol Monitor Model 8520. MDPH staff also performed visual inspection of building materials for water damage and/or microbial growth.
The school houses approximately 1,200 elementary students in grades 3 to 5 with approximately 125 staff members. Tests were taken during normal operations at the school and results appear in Tables 1 and 2.
It can be seen from Tables 1 and 2 that carbon dioxide levels were above 800 parts per million (ppm) in 17 of 49 areas on February 15, and in 27 of 48 on February 26, 2008. These levels of carbon dioxide indicate a poor air exchange in a number of areas. Elevated levels of carbon dioxide are largely the result of deactivated mechanical ventilation equipment. It is also important to note that several classrooms had open windows and/or were empty/sparsely populated, which can greatly reduce carbon dioxide levels. Carbon dioxide levels would be expected to increase with full occupancy and windows closed.
Fresh air is supplied to classrooms by unit ventilator (univent) systems (Picture 1). A univent draws air from the outdoors through a fresh air intake located on the exterior wall of the building (Picture 2) and returns air through an air intake located at the base of the unit (Figure 1). Fresh and return air are mixed, filtered, heated and provided to classrooms through an air diffuser located in the top of the unit. Univents were found obstructed by furniture, books and other stored materials (Picture 3). Further, a heavy buildup of dust and debris was observed in the air diffusers of several univents. In one particular room, BEH staff opened the univent to find a buildup of dirt, dust and debris as well as disintegrating fiberglass insulation (Pictures 4 and 5/Table 1). In order for univents to provide fresh air as designed, air diffusers, intakes and returns must remain free of obstructions. Importantly, these units must remain “on” and be allowed to operate while rooms are occupied.
Exhaust ventilation in classrooms is provided by ceiling and wall-mounted vents (Picture 6) ducted to rooftop motors. Exhaust ventilation was deactivated in a number of areas during the assessment (Table 1). As with univents, in order to function properly, exhaust vents must be activated and allowed to operate while rooms are occupied. Without adequate supply and exhaust ventilation, excess heat and environmental pollutants can build up leading to indoor air/comfort complaints. Also of note was a breach in the ductwork in classroom A-214 (Picture 7), which can reduce the efficiency of the exhaust system.
Ventilation for common areas (e.g., gym, cafeteria) is provided by rooftop or ceiling-mounted air-handling units (AHUs). Fresh air is distributed via wall/ceiling-mounted air diffusers and ducted back to AHUs via ceiling or wall-mounted return vents. As with univents, AHUs should be activated and allowed to operate continuously during occupied periods.
To maximize air exchange, the MDPH recommends that both supply and exhaust ventilation operate continuously during periods of school occupancy. In order to have proper ventilation with a mechanical supply and exhaust system, the systems must be balanced to provide an adequate amount of fresh air to the interior of a room while removing stale air from the room. It is recommended that HVAC systems be re-balanced every five years to ensure adequate air systems function (SMACNA, 1994). The systems at JJES were reportedly balanced upon installation in 1991 and most recently in 2002.
The Massachusetts Building Code requires a minimum ventilation rate of 15 cubic feet per minute (cfm) per occupant of fresh outside air or have openable windows in each room (SBBRS, 1997; BOCA, 1993). The ventilation must be on at all times that the room is occupied. Providing adequate fresh air ventilation with open windows and maintaining the temperature in the comfort range during the cold weather season is impractical. Mechanical ventilation is usually required to provide adequate fresh air ventilation.
Carbon dioxide is not a problem in and of itself. It is used as an indicator of the adequacy of the fresh air ventilation. As carbon dioxide levels rise, it indicates that the ventilating system is malfunctioning or the design occupancy of the room is being exceeded. When this happens, a buildup of common indoor air pollutants can occur, leading to discomfort or health complaints. The Occupational Safety and Health Administration (OSHA) standard for carbon dioxide is 5,000 parts per million parts of air (ppm). Workers may be exposed to this level for 40 hours/week, based on a time-weighted average (OSHA, 1997).
The MDPH uses a guideline of 800 ppm for publicly occupied buildings. A guideline of 600 ppm or less is preferred in schools due to the fact that the majority of occupants are young and considered to be a more sensitive population in the evaluation of environmental health status. Inadequate ventilation and/or elevated temperatures are major causes of complaints such as respiratory, eye, nose and throat irritation, lethargy and headaches. For more information concerning carbon dioxide, consult Appendix A.
Temperature measurements ranged from 70 º F to 76 º F on February 15 and from 67 º F to 74 º F on February 26, 2008 (Tables 1 and 2). These measurements were within or close to the lower end of the MDPH recommended comfort range on both days of the assessment. The MDPH recommends that indoor air temperatures be maintained in a range of 70o F to 78o F in order to provide for the comfort of building occupants. In many cases concerning indoor air quality, fluctuations of temperature in occupied spaces are typically experienced, even in a building with an adequate fresh air supply. In addition, it is often difficult to control temperature and maintain comfort without operating the ventilation equipment as designed (e.g., univents/exhaust vents deactivated/obstructed).
The relative humidity measured in the building ranged from 18 to 30 percent on February 15, and from 16 to 25 percent on February 26, 2008 (Tables 1 and 2). Relative humidity measurements werebelow the MDPH recommended comfort range in all areas surveyed on both days of the assessment. The MDPH recommends a comfort range of 40 to 60 percent for indoor air relative humidity. Relative humidity levels in the building would be expected to drop during the winter months due to heating. The sensation of dryness and irritation is common in a low relative humidity environment. Low relative humidity is a very common problem during the heating season in the northeast part of the United States.
Several classrooms had water-damaged ceiling tiles which can indicate sources of water penetration (Tables 1 and 2). Water-damaged ceiling tiles can provide a source of mold and should be replaced after a water leak is discovered and repaired.
Open seams between sink countertops and walls were observed in several rooms (Picture 8). If not watertight, moisture can penetrate through the seam, causing water damage. Improper drainage or sink overflow can lead to water penetration into the countertop, cabinet interior and areas behind cabinets. Water penetration and chronic exposure of porous and wood-based materials can cause these materials to swell and show signs of water damage.
The US Environmental Protection Agency (US EPA) and the American Conference of Governmental Industrial Hygienists (ACGIH) recommend that porous materials be dried with fans and heating within 24 to 48 hours of becoming wet (US EPA, 2001; ACGIH, 1989). If not dried within this time frame, mold growth may occur. Once mold has colonized porous materials, they are difficult to clean and should be removed/discarded.
Some classrooms were equipped with exterior doors. Several of these doors had damaged weather stripping, and light could be seen penetrating through the spaces underneath the door from the outdoors (Picture 9). Spaces beneath exterior doors can serve as a source of water entry into the building, causing water damage and potentially leading to mold growth. In addition, these spaces can serve as pathways for insects, rodents and other pests into the building.
Several classrooms had a number of plants (Picture 10). Moistened plant soil and drip pans can be a source of mold growth. Plants should be equipped with drip pans; the lack of drip pans can lead to water pooling and mold growth on windowsills. Plants are also a source of pollen. Terrariums were observed in some classrooms in close proximity to classroom univents (Picture 10). Terrariums should be properly maintained to ensure soil does not become a source for mold growth. Plants and terrariums should also be located away from univents to prevent the aerosolization of dirt, mold, pollen, odors or particulate matter throughout the classroom.
BEH staff examined the building exterior to identify breaches in the building envelope that could provide a source of water penetration. Several potential sources were identified:
Missing/damaged sealant between expansion joints (Pictures 11 and 12);
Gutters/downspouts were damaged and emptying against the exterior of the building, allowing rainwater to pool on the ground at the base of the building (Picture 13);
Open utility holes (Picture 14); and
Plants/debris in/near univent fresh air intakes (Picture 15).
The conditions listed above can undermine the integrity of the building envelope and create/provide a means of water entry by capillary action into the building through exterior walls, foundation concrete and masonry (Lstiburek & Brennan, 2001). The freezing and thawing action of water during the winter months can create cracks and fissures in the foundation. In addition, they can serve as pathways for insects, rodents and other pests into the building.