As schools across the country prepare for winter—closing windows, firing up the furnaces and bringing students in from the chill—it is time to pay closer attention to indoor air quality. The statistics are sobering: 32 million of the nation's 54 million school kids are at elevated risk for health and learning problems due to the condition of their schools. IAQ is reported to be unsatisfactory in about one in five public schools in the United States, while ventilation is reported as unsatisfactory in about one-quarter of public schools.

Upgrading your air filtration system with mechano-electret filters may prove to be a
simple and low-cost step toward improving the health of your school environment.

Health and Learning
Why is IAQ so important in schools? Evidence continues to mount that IAQ directly impacts student academic performance and health.

One of the biggest health problems linked to poor IAQ is asthma. Nearly 1 in 13 schoolage children has asthma. There is evidence that indoor environmental exposure to allergens commonly found in schools—such as dust mites, pests, and molds —plays a role in triggering asthma symptoms.

Asthma is costly and a primary cause of school absenteeism, accounting for 10 million to nearly 13 million missed school days per year. Moreover, absenteeism directly affects school funding, which is often based on attendance.

Absenteeism linked to poor IAQ does not just affect students; it also affects the health, productivity and job satisfaction of teachers and staff. Nearly 80 percent of teachers responding to a survey in Chicago and the District of Columbia reported that school facility conditions were an important factor in teaching quality. Almost half of those who graded their facilities "C" or below would consider leaving; the most frequently cited problem was bad IAQ.

Asthma is not the only health problem linked to poor IAQ. Students, teachers and staff also may be at risk for headache, dizziness, nausea, allergy attacks, respiratory problems, and sometimes life threatening conditions, such as Legionnaire's disease and carbon monoxide poisoning.

Improved Air Filtration Improves IAQ
IAQ may be significantly improved in schools with the proper HVAC air filtration strategy. A key component of a good air filtration strategy is choosing the right air filters— a decision that should be based, in part, on filter efficiency.

To evaluate filter efficiency, many people turn to MERV. The Minimum Efficiency Reporting Value is assigned to filters based on their minimum fractional particle size efficiency, as determined under the ASHRAE 52.2 Standard.

While MERV does provide some basic information for evaluating filter performance, there is a better and more complete way to compare filtration efficiencies of different air filters: by reviewing the efficiency values included in the ASHRAE 52.2. test report.

The ASHRAE 52.2 test provides the efficiency of the filter over three particle size ranges: E1 (very fine particles in the 0.3 to 1.0 micrometer range), E2 (fine particles in the 1.0 to 3.0 micrometer range), and E3 (coarse particles in the 3.0 to 10.0 micrometer range). The E1, E2 and E3 efficiencies represent the true measure of filter performance and give users a more complete picture of what particles a filter is capable of removing from the airstream. A MERV of 5 is least efficient, while a rating of 16 is most efficient.

High E1 and E2 efficiencies are critical for good IAQ. Most of the respirable dust and particles people breathe into their lungs is three micrometers and smaller. Lung-damaging dust, for example, can be as small as 0.5 micrometers while bacteria can be as small as 0.3 micrometers. MERV ratings do not even begin to consider filtration efficiency for the respirable E1 particle sizes until MERV 13.

Selecting Air Filters to Enhance IAQ
When specifying air filters, it is best to look at filters with filtration media that provides a good balance of mechanical and electret efficiency. Filters that utilize mechano-electret media will almost always outperform filters that rely solely on mechanical efficiency, especially for respirable E1 particles.

The mechanical efficiency of these filters provides for sustained filtration efficiency, and the electret charge increases initial efficiency, which is particularly useful for capturing E1 submicron particles. This is because, while submicron particles are much smaller than the void spaces in most commercial electret media, the electrostatic forces within the media structure allow those E1 submicron particles to be removed with high efficiency.

Mechano-electret filters also typically deliver lower airflow resistance than mechanical-only filters, which helps to reduce energy consumption and cost. The best mechano-electret filters have a depth-loading media with a gradient density structure. This combination can help to reduce airflow resistance, while enhancing dust holding capacity by reducing face loading of the filter.

Smart filter selection and proper filter maintenance are crucial to achieving and maintaining good IAQ. A number of organizations address filter selection and maintenance. The American Federation of Teachers, for example, recommends using air filters with 70-85 percent efficiency and to change those filters when they reach the manufacturer- recommended pressure differential. CHPS (The Collaborative for High Performance Schools) calls for MERV 13 or 85% efficiency filters as long as the filters do not compromise system performance by reducing airflow or increasing fan energy use.

The EPA also has air filtration recommendations for schools, including:

• Minimum 2 inch thick filter slots— For better protection of the indoor environment, equipment and ducts.
• Extended surface area filter bank—To reduce the frequency of filter maintenance and the cost of fan energy, the bank is designed to allow more filter area, such as the deep V approach or bags.
• Air filter assemblies (racks & housings) designed for minimum leak age—The filter bank should have gaskets and sealants at all points where air could easily bypass the air filters, such as between the filterrack and the access door. Use properly gasketed manufacturersupplied filter rack spacers.
• Air filter monitor—A differential pressure gauge to indicate the static pressure drop across the filter bank. It has been estimated that a 30% increase in static pressure across a filter results in a $200 per 10,000 cfm of air movement (at 7 cents per KWH). This does not include the added cost of cleaning dirty heating or cooling oils, drain pans, or air ducts.
• Air filters should have a MERV of between 8 and 13—The higher the rating, the better the protection for the equipment and the occupants. Consider specifying a low efficiency MERV 6 (~10%) prefilter up stream of the main filters.

Additional Guidance
There are several resources available for school administrators and facilities professionals looking to improve IAQ in their schools.

The EPA's Tools for Schools program is a comprehensive resource to help schools maintain a healthy environment in school buildings by identifying, correcting and preventing IAQ problems. According to the EPA, improving IAQ with programs such as Tools for Schools, has led to health and productivity benefits among students and cost reductions for maintenance and operations.

CHPS (Collaborative for High Performance Schools) helps facilitate and inspire change in the educational system by focusing on the design, construction and operation of high performance schools: environments that are not only energy and resource efficient but also healthy, comfortable, well lit, and containing the amenities for a quality education. CHPS's Best Practices Manual addresses HVAC and IAQ issues in its Maintenance & Operations section.

The National Clearinghouse for Educational Facilities (a program of the National Institute of Building Sciences) provides timely, comprehensive information on designing, building and maintaining safe, healthy, high-performing schools.

NIOSH offers a checklist that covers general recommendations for addressing IAQ issues in schools.

The American Federation of Teachers offers a White Paper titled "What You Should Know about Indoor Air Quality" that calls for teachers to take action if suffering from IAQ problems like Sick Building Syndrome—a situation in which building occupants experience acute health and comfort-effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified.

Conclusion
A recent review by Carnegie Mellon of five separate studies found an average reduction of 38.5 percent in asthma in buildings with good IAQ.

Beyond reducing asthma symptoms, improving the indoor air quality in our nation's schools is "right" thing to do. According to the EPA, preventing or responding promptly to IAQ problems can:

• Reduce potential for long- and short-term health problems for students and staff.
• Positively impact student attendance, comfort, and performance.
• Increase teacher and staff comfort and performance.
• Reduce the rate of deterioration and increase efficiency of school facilities and equipment.
• Reduce potential for school closings or relocation of occupants.
• Enhance relationships among school administration, parents, and staff.
• Create positive publicity.
• Enhance community trust.
• Reduce liability problems.

For these reasons and more, now is the perfect time to put indoor air quality on the curriculum at your school. Upgrading your air filtration system with filters that utilize electro-mechanical media may prove to be a simple and low-cost step toward improving the health of your school environment.

Tony Fedel, P.E., Market Manager, Kimberly-Clark Professional Filtration. For more information on how to evaluate the performance of various types of air filter media technology, visit www. kcfiltration.com.

Back to top ▲