Airing it Out

Oct. 1, 2000
Proper maintenance can help schools eliminate the unseen culprits that endanger indoor air quality.

Proper maintenance can help schools eliminate the unseen culprits that endanger indoor air quality.

Students enrolled this year at Lafayette School in Everett, Mass., did not begin classes at the end of August as scheduled. The night before classes were to start, the city's building commission ordered the school to close for at least a week because of concerns about indoor air quality (IAQ).

The Lafayette School is only one example of a potentially serious problem that most schools and universities struggle with. Poor indoor air quality can cause short- and long-term health complications ranging from runny noses to asthma - a disease that affects 1 in 13 young people.

In 1995, the Environmental Protection Agency determined that facility-related problems adversely affected IAQ in more than 50 percent of the nation's schools. Most of these instances involved failed or improperly maintained equipment.

HVAC MAINTENANCE Heating/ventilation/air-conditioning (HVAC) systems require significant preventive maintenance to ensure healthy IAQ levels. So, facility managers need to be aware of the following:

- Drain pans and traps: Trays that are improperly designed or maintained can lead to inadequate IAQ. Every piece of equipment delivering air-conditioned air has a drain pan and associated trap. Air-conditioning coils cause water to condense; it is collected in the drain pan and piped to a system to carry away the wastewater.

A drain trap is installed between the drain pan and the piping system to ensure that the water flows away from the equipment. Dirty drain pans that prevent water from flowing properly are havens for microbial growth.

Drain pans should have an air gap to prevent gases from being drawn back in from the piping system. Backed drains can cause water to overflow from the drain pain, which will cause other elements of the system to foster bacterial growth.

- Filter selection guidelines: Ten years ago, filters were used primarily to keep HVAC equipment clean, rather than to make the air healthier. Today, maintenance plans place much more emphasis on the comfort and well-being of a building's inhabitants. For schools to achieve adequate indoor air quality, particles larger than 0.3 microns, which can negatively affect the human respiratory system, must be kept to a minimum.

Facility managers should install filtration systems capable of removing 0.3-micron particles from the air. A filtration system should remove at least 60 percent of all 0.3-micron particles in order for it to be effective. Some remove up to 95 percent of all large particles from the air, while others only remove 30 percent to 35 percent.

Schools and universities can refer to the American Society of Heating Refrigeration and Air-conditioning Engineers (ASHRAE) 52-76 standard, which rates the efficiency of various filters. Facility managers should not upgrade a building's filters without determining that the system can handle the increased airflow resistance associated with higher-efficiency filters. And installing a high-efficiency filter without recalibrating the air system can reduce airflow.

Facility managers should make sure that workers properly install and secure the filters, sealing any gaps between the filters and the unit. They also should check access doors for proper sealing. Finally, they must replace filters regularly to prevent clogging, which reduces air flow.

BACTERIAL BREEDING GROUNDS Some places to check for bacteria:

- Cooling towers. Cooling towers use water to reject heat from cooling equipment such as chillers. If improperly maintained, they can cause a variety of IAQ problems. Because they can serve as breeding grounds for bacteria such as Legionella, qualified chemical treatment specialists should conduct periodic water tests. Facility managers should install a system to deliver necessary chemicals to the water.

Slime and algae are definite signs of bacteria growth in the cooling tower sump, as well as within the spray area. If bacteria are present, only properly protected, qualified technicians should administer cleaning. Any leaks or overflow problems should be repaired as well.

Facility managers also should conduct quarterly inspections for bacteria growth, tower overflow and effluent drift - the steam emitted from the towers. The effluent from a cooling tower must be far from outdoor-air intakes and openings. If the steam a tower emits is contaminated, it will pollute a building's upper floors and roof, as well as the surrounding area. Drift eliminators can prevent this problem.

- Humidifiers. Humidifiers typically are installed in humidity-sensitive areas such as computer rooms, libraries and museums to bring humidity levels within the acceptable range (usually 20 percent to 30 percent relative humidity). Ironically, humidifiers installed to help improve indoor air quality can be a major cause of IAQ problems.

Different types of humidifiers deliver humidity to spaces the same way - by adding steam to the air - and all of them have the same potential for attributing to IAQ problems. If a humidifier is too large for a space or is not operated properly, it can increase the humidity level in the duct stream to greater than 70 percent - the level that supports biological growth. The risk for breeding bacteria increases dramatically if an air system is dirty or a duct liner is used in the air stream. Usually, humidifiers have a duct high- humidity limit, which shuts the humidifier down when the air stream becomes too moist. The duct high-humidity limit should be tested monthly during the heating season to ensure that it is calibrated properly and shuts the humidifier down if high levels of humidity occur.

For guidelines on acceptable temperature and humidity levels, schools and universities can look to ASHRAE 55-1981 (ASHRAE's website is

AIR POLLUTION Other things that affect the air to watch out for include:

- Boilers. Leaking boiler flues and stacks positioned too closely to air intakes contribute to IAQ problems by permitting exhaust such as carbon monoxide to inadvertently enter the building. Facility managers should conduct monthly inspections during the heating season to ensure proper flue drafting, and that the flue and fuel systems are not leaking. Often, a flue will draft properly except on certain days when the prevailing wind may permit flue gases to enter through an improperly placed intake opening.

Gas or oil leaks from a boiler not only are fire hazards, but also can cause health problems. A qualified and properly protected technician should repair leaks as soon as possible.

- Ventilation codes and standards. The predominant standard for ventilation is ASHRAE's Ventilation for Acceptable Indoor Air, 62-1989. Most state building codes either are based on or refer to this standard. The standard includes a table listing, space types and the amount of outdoor air required to achieve acceptable IAQ. The ventilation code is based on the following three assumptions:

- Enough outside air is provided to dilute internally generated contaminated air.

- The outdoor air being used for ventilation is clean.

- The supply air to the rooms obtains 100 percent mixing or ventilation effectiveness.

Unfortunately, it is rare for all three of these factors to be present in schools and universities. In best cases, schools achieve a ventilation effective rate of 80 percent. But even in facilities with adequate ventilation, much of the mixing occurs above the occupants' heads and leaves the room through the return register before it has a chance to ventilate the room. Therefore, schools should have vents at a height and angle that allows mixing to occur throughout a classroom.

Testing has shown that 20 percent of schools and universities have contaminant levels that are too high. Often, new and renovated buildings have an unacceptably high level of volatile organic compounds from new furniture, rugs or office equipment.

In many urban areas, outside air contains too many contaminants to be considered acceptable. Schools can check their regions' outdoor air quality through their state or regional Environmental Protection Agency (EPA) offices. But schools and universities also need to consider contaminant sources such as street traffic and exhaust from neighboring buildings that may not be factored into the EPA's findings.

Often architectural constraints, rather than health and comfort, determine the location of a building's air intakes. Generally, these air intake sites work 90 percent of the time. However, continually changing conditions, such as wind direction or an idling truck, can generate temporarily contaminated outdoor air. Buildings near airports and highways deserve special attention, because outdoor pollution can vary greatly.

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