Renovation activities can create indoor air quality (IAQ) problems through normal construction processes that distribute existing materials, as well as through introduction of new materials. In some cases, furnishings and mechanical systems become contaminated by these pollutants, and often act as pollutant "sinks" by spreading or adsorbing volatile contaminants and then serving as long-term emission sources.
It is important to note that not every construction process requires extensive preventative procedures. For example, touch-up painting in a mechanical room or storage area that is not occupied by students or faculty may only require ventilation.
Sources and hazards There are five types of contaminants that administrators must pay attention to when renovating: -Volatile and semi-volatile organic compounds. These are compounds that are readily volatilized from building materials. Semi-volatile organic compounds are defined as those that will be volatilized, but at a slower rate. Sources known to be emitters of VOCs include protective coatings, sealants, paints, stains, varnishes, adhesives, caulking compounds, carpeting, resilient floor coverings and wall coverings. Minimizing building occupant exposure to VOCs is a responsible and reasonable policy.
-Dust and fibers. These pollutants often are released through cutting and sanding, as well as by disturbing areas where dusts and fibers have accumulated over time. These nuisance dusts do not cause lung fibrosis or systemic health effects, and are generally thought to be nontoxic unless present at high concentrations. What can become more of a problem is dust generated by disturbing lead-based paint. While the dust is an inhalation hazard, it may be ingested when contaminated fingers and hands are placed in the mouth.
Fibers commonly encountered include fiberglass and asbestos. Fibers can cause skin irritation. When dealing with asbestos, schools are required by the Asbestos Hazard Emergency Response Act to have asbestos management plans in place that identify all of the asbestos-containing materials in the building.
-Gases. Combustion sources often used during renovation projects emit various gases. For example, internal combustion engines and space heaters produce carbon monoxide, carbon dioxide, nitrogen oxides and sulfur dioxide. Welding processes can produce ozone, as well as carbon monoxide and nitrogen oxides.
-Bioaerosols. Biological pollutant sources include outdoor air, people carrying viruses and bacteria, and various animals that shed allergens. These airborne materials have been shown to produce infections, hypersensitivity diseases involving immune system activation and toxicoses.
-Physical agents. Renovation activities can introduce physical stressors-noise, vibration, and create uncomfortable temperature or humidity. These stressors can impact the ability to concentrate and communicate.
Control strategies Administrators can take steps to reduce the likelihood that renovation projects will create IAQ problems, including: -Early identification of hazards presented by the existing building materials, furnishings and equipment. If the building was constructed before 1980, utilize the services of a trained professional to perform a lead paint inspection. This is not needed if studies have been completed, documented, and contain the required information.
-Selecting appropriate new building materials. Be sure to specify low-VOC emitting paints, adhesives and composite materials. Obtain a material safety data sheet for each product considered. Ask manufacturers to supply the material contents of each product, as well as the identification and quantified amounts of substances that are listed on the International Agency for Research on Cancer List of Chemical Carcinogens; the Carcinogen List of the National Toxicology Program; and the Reproductive Toxin List of the Catalog of Teratogenic Agents. Larger school systems or a consortium of school systems may want to ask for more information when products are used in larger quantities.
-Storing and installing new materials properly. Schools can take steps to reduce IAQ impacts on new building materials. For example, air out carpeting, vinyl flooring, workstation panels and other fabrics to reduce residual VOC levels. For wet products, require the manufacturers to specify procedures that allow for the smallest quantities of the products to be used, consistent with performance requirements. Make sure any stored products are protected against water damage and high humidity to guard against mold growth.
-Selecting and applying ventilation controls, and utilizing temporary barriers. There are two types of ventilation that are utilized to control indoor pollutants-dilution and local exhaust combined with isolation techniques. A local exhaust system may be as simple as setting up floor fans and/or window fans to ventilate directly outside. Another method is to set up portable ventilation units with flexible ducting.
If the school's HVAC system is used for exhausting air from the space, avoid contamination of the system. Toxic dusts may be generated from demolition and surface preparation, and these dust accumulate within the system and become dislodged and entrained in the air being handled by the system later. Install temporary filters at the face of each return grille to reduce contamination. However, it is best to avoid using the school's HVAC for filtration.
-Minimizing release of pollutants through applying good housekeeping and work practices. Workplace preparation should include removing or protecting as many items of furniture as possible. Pay careful attention to workers and equipment leaving the renovation area to avoid carrying dusts and fibers outside of the work area. Effective practices include providing walk-off mats at exits and having workers remove coveralls and wipe down equipment before leaving the work area. Other common practices include placing lids back on containers after usage, pour materials back into containers and seal before taking breaks, clean up spills as soon as possible, and adhere to manufacturers' recommended product installation/applications procedures.
-Minimizing exposure through appropriate scheduling. Whenever possible, major work should be scheduled during unoccupied periods or periods of least occupancy. Make sure scheduling information is given to school administrators, teachers, maintenance and operations staff, contractors, parents and students, as appropriate.
-Relocating susceptible individuals. It is best to move as many people as possible away from potential pollutants. Classrooms may be able to be moved or students can be relocated to another building. Another option for hypersensitive students may be home instruction for a period of time.
-Communicating with all impacted personnel. Establish a strong, proactive communication and notification program. This should include early involvement of the school principal, response to problems and emergencies, and communication with affected parties.
-Utilizing a management-control system during the project. Small projects may be administered, on a collateral duty basis, by an appropriate staff person. Larger projects will warrant regular oversight and monitoring, and for managing a permit system that requires sign-off before each major phase can proceed. -Incorporating these practices into the bid specifications.
Establishing guidelines It is important to establish IAQ close-out-acceptance-criteria for all renovation projects. When it comes to general cleaning, require that all surfaces be wet-wiped and all areas cleaned with vacuums that are HEPA-equipped for fine and/or potentially toxic dusts. Specify portions or components of the HVAC system that must be cleaned, and establish inspection criteria to be followed. If any system modifications have been done, balance and test the HVAC system. Be sure to dispose of filters that may have been contaminated during the renovation.
Also, each HVAC system should be tested and verified for each mode of operation, including occupied/unoccupied, warm-up/cool-down, ventilation cycle, and emergency power supply.
Test all supply, return, exhaust and outdoor airflow rates; control settings and operation; air temperature; fan speeds and power consumption; and filter resistance. If the HVAC system is renovated, then a commissioning process such as that described in ASHRAE guideline 1-1989, should be done. This verifies that performance meets design intent, generates appropriate system documentation, and trains operation and maintenance personnel.
When selecting HVAC systems for schools, it is important to balance the need for indoor air quality, energy conservation and maintenance. At a minimum, designers of HVAC systems must be guided by building codes and industry standards regarding ventilation rates and energy use. Capital cost budgets may limit the choice of system or its quality, inadvertently obscuring the basic objective to provide a comfortable, healthy environment conducive to effective learning.
When selecting an HVAC system, consider the following criteria: -Temperature and humidity. ASHRAE standard 55-1992, Thermal Environmental Conditions for Human Occupancy, defines comfort temperature and relative humidity conditions for summer and winter. A year-round average of 72 degrees F to 76 degrees F is generally acceptable. Maintaining relative humidity between 30 and 60 percent basically is a health consideration.
*Indoor air quality. The concentration of contaminants within the classroom are the result of emission rates from internal sources and the rate of dilution through the supply of relatively contaminant-free air. Filters with an ASHRAE dust spot efficiency of 25 percent or more can provide superior protection of HVAC components exposed to the air compared to the coarse fiber or metal filters typically furnished with manufactured equipment.
*Acoustics. Noise from equipment within the classroom, emanating from air outlets or radiating through ceilings can be disruptive. The ASHRAE Fundamentals Handbook recommends a criterion for classroom sound of NC-30 as an acceptable system noise level for the range of speech communication frequencies.
-Energy use. Construction projects can be assigned an energy budget, usually expressed in BTU/Ft2/year. -Operation and maintenance. Improper operation and neglectful maintenance have been identified as major causes of poor IAQ. Match equipment with the level of training of staff.
-Staffing and standardization. Knowledge of the staff and standardized procedures and procurement practices can aid in system and component selection. -Preventive maintenance. Well-planned, documented regular maintenance procedures should be an integral part of any IAQ program. -Automation and monitoring. Automated direct digital control with off-site monitoring is likely to be a preferred choice. -Flexibility. Ability to meet changes in classroom usage or function will differ among systems and could be a significant factor in system selection. -Vandalproofing. Passive protective measures are more readily accomplished with some systems than others. -Capital cost. Budget decisions should be based on solid value judgments, not just initial cost.
System selection There are different types of HVAC systems, including: -Unit ventilators. These have been the most popular method of heating, ventilating and cooling for schools for years. Basic components include outdoor and recirculating air inlets with automatic dampers, filter, heating and cooling coils, and fan section. Keep in mind that these have no recirculation of air between classrooms. They feature independent classroom control and operation, and constant volume air flow. For some schools, the lack of duct work and central air handling equipment is a plus.
-Variable air volume. This is probably the second most frequently selected system for schools. Both recirculated and outdoor air for ventilation and cooling are blended, filtered, cooled and sometimes heated and humidified in an air-handling unit serving multiple spaces. A benefit is that medium or high-efficiency filters can be applied, and less fan and reheat energy is needed than with constant volume systems. However, note that unless terminals are fan powered, supply air is below design for much of the school year.
-Single zone systems. This is a single air-conditioning unit located near the spaces served, often on the roof above, and usually conditions one classroom. The unit can be factory built with integral air cooled refrigeration and compact for installation. The first cost is often less than other systems for smaller schools, and medium-efficiency filters can be selected. However, for larger facilities, the space needs for units and connecting ducts may prove impractical. (BULLET)Multizone units. Multizone, often packaged with air-cooled refrigeration and heating for roof mounting, can serve six or more rooms. The supply to each is divided into two or three alternative ducted pathways equipped with automatic dampers that respond to the zone thermostat to bypass the cooling coil to regulate the zone temperature. The first cost can be lower than single zone for clusters of classrooms and temperature control can be proportional for heating and cooling. With a separate supply for each classroom, ductwork can become extensive, both costly and space consuming.
-Water source heat pumps. In this setup, each classroom is served by a water source heat pump containing a reversible refrigeration unit. For cooling, air is circulated through the refrigerant chilled coil; heat is rejected into a closed loop water distribution system from which it is typically removed through heat exchange to a cooling tower and expelled to the atmosphere. To heat the room, the refrigeration cycle is reversed. One advantage is that heating or cooling for each space is available year round, and central refrigeration plants are not needed. However, most units are not designed to heat or cool large proportions of untempered outdoor air.
-Separate ventilation air system. This approach is being applied to overcome indoor air quality problems and to upgrade existing systems to current standards. Outdoor air-filtered, heated, cooled, dehumidified, humidified-in a central air-handling unit is supplied by ductwork to the classroom either through the unitary equipment or through ceiling diffusers. Airflow may be constant or under demand control.
Creating resources More than a decade ago, the Maryland State Department of Education realized that the 24 school districts within the state needed some guidance when it came to indoor air quality. The result is a stack of technical bulletins, a grant program, workshops and an award recognition program.
"We have had a very good response to our program," says Allen Abend, chief of school facilities branch, Maryland State Department of Education. "The available information out there often was very bias, very complex and somewhat misleading. We wanted to make it easier for school systems to manage this issue; to do the best job they can. We wanted to get into the hands of the school system a management tool to help them deal with indoor air quality; so they are prepared when a problem arises and can respond."
The program, which began in 1986, involved selecting a school district to work with and develop a comprehensive management IAQ program, which would then be used to teach other districts. The department of education chose Anne Arundel County Public Schools, developing a program that has been in use since 1989 across the state.
In 1991, the state hosted workshops with two representatives from each of the 24 school districts. The workshops trained these individuals to be inspectors and investigators for indoor air quality problems. The next step was the development of about a dozen technical bulletins on such topics as carpet and IAQ, science labs and IAQ, as well as HVAC and IAQ.
"We also just completed our third year of IAQ management in schools award program," says Abend. "The purpose is to recognize school systems that have implemented good management strategies for IAQ and to provide some rewards for their efforts. Also, we make presentations and award governor citations to school systems with successful nominations at the local board of education meetings."
Maryland's program is voluntary, yet the response rate is very high.