At the request of Mr. Carl Wicklund, Facilities Manager for Leicester Public Schools, the Massachusetts Department of Public Health (MDPH), Bureau of Environmental Health (BEH) conducted an indoor air quality (IAQ) assessment at the Leicester Memorial School (LMS) located at 11 Memorial School Drive, Leicester, MA. The request was prompted by general indoor air quality complaints and deteriorating building conditions. On April 7, 2011, a visit to conduct a general IAQ assessment was made to the LMS by Lisa Hébert, Environmental Analyst/Regional Inspector for BEH’s IAQ Program.
The school is a two-story brick building constructed in 1954 as the former Leicester Junior High School. The school was converted into an elementary school circa 1995. The roof was reportedly replaced approximately four years ago to control water infiltration. Windows are openable throughout the building. It was reported to BEH staff that the school is in the process of replacing hallway carpeting with vinyl floor tile.
Air tests for carbon monoxide, carbon dioxide, temperature and relative humidity were conducted with the TSI, Q-Trak, IAQ Monitor, Model 7565. Air tests for airborne particle matter with a diameter less than 2.5 micrometers were taken with the TSI, DUSTTRAK™ Aerosol Monitor, Model 8520. BEH staff also performed visual inspection of building materials for water damage and/or microbial growth.
This school houses approximately 420 third to fifth grade students and approximately 50 staff members. Tests were taken under normal operating conditions. Test results appear in Table 1.
It can be seen from Table 1 that carbon dioxide levels were above 800 parts per million (ppm) in twenty of thirty-five areas surveyed. Of note was that carbon dioxide levels in the art room exceeded 2,000 ppm. The elevated carbon dioxide levels measured in most areas of the school indicate poor air exchange throughout the building, particularly in classrooms that were fully occupied. These levels are due to deactivated/non-functioning/poorly functioning ventilation equipment. It is also important to note that some areas were empty/sparsely populated, which can greatly reduce carbon dioxide levels. Carbon dioxide levels would be expected to increase with higher room occupancy.
Fresh air in classrooms throughout the school is supplied 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. Fresh and return air are mixed, filtered, heated and provided to classrooms through an air diffuser located in the top of the unit (Figure 1). Univents were found deactivated during the assessment, therefore no mechanical means of introduction of fresh air was being provided. Univents were also obstructed by items such as chairs, tables, desks, and books (Picture 3). In order to function as designed, univents must be activated and allowed to operate free of obstructions. Also noted within the air handling cabinets of univents were spaces through the concrete floor around utility pipes (Pictures 4 and 5). These breaches can create a pathway of migration for moisture, odors and/or particulates to be drawn from the crawlspace where it can be distributed by the univent into occupied areas.
Many of the univents at the LMS appeared to have been installed when the school was built in 1954. According to the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), the service life1 for a unit heater, hot water or steam is 20 years, assuming routine maintenance of the equipment (ASHRAE, 1991). The operational lifespan of this equipment has long passed. Given its age, continuing to maintain the balance of fresh air to exhaust air will be difficult at best.
Exhaust ventilation in classrooms is provided by hearth-like structures at the base of walls that are connected to exhaust vents on the roof. At the time of the assessment, the exhaust system was found deactivated in many areas (Table 1). In addition, several classrooms had exhaust vents that were either shut or obstructed by various items (Picture 6). As with the univents, exhaust vents need to be activated and free from obstruction to function as designed. Without adequate supply and exhaust ventilation, excess heat and environmental pollutants can build up and lead to indoor air/comfort complaints.
To maximize air exchange, the MDPH recommends that both supply and exhaust ventilation operate continuously during periods of building 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 system has reportedly not been balanced due to budgetary constraints.
The Massachusetts Building Code requires that each room have a minimum ventilation rate of 15 cubic feet per minute (cfm) per occupant of fresh outside air or openable windows (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 68°F to 76°F, which were within or close to the MDPH recommended comfort range at the time of the assessment (Table 1). 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. Given the age, condition and operating status of ventilation equipment, temperature control would be expected to be difficult.
The relative humidity measured in the building ranged from 17 to 35 percent which was below the MDPH recommended comfort range (Table 1). 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.