In a world where local factory smoke stacks, house chimneys, engine exhaust, dust, mold, and pollen all accumulate into air pollution levels that can become downright unhealthy, improving air quality is vital. None of those contaminants get filtered out before outdoor air infiltrates your home. Furthermore, the average home contributes even more pollutants to that already filthy air. Fumes from solvents, cleaning products, carpet adhesives, candles, incense, interior paints, tobacco smoke, pet dander, dust, dust mites, and indoor mold factor into an indoor air pollution level that can be even worse than outside air.
It’s clear that, in order to remain healthy, improving home air quality is crucial – so what are the best ways to accomplish that? The United States Environmental Protection Agency (EPA) recommends the following 10 key steps to improve indoor air quality:
- Control pollution sources - Either eliminate individual sources or take steps to reduce their emissions.
- Ventilation - Increase the intake of outdoor air to dilute concentrations of indoor pollutants. Open doors, and windows, or run air conditioning with the vent control open. Bathroom and kitchen exhaust fans that are ventilated to the outside can also help.
- Adjust Humidity - The ideal range is between 30 and 50 percent. Purchase of a moisture or humidity gauge, available at most hardware stores, is recommended. To increase humidity, use a vaporizer or humidifier. To decrease humidity, open windows if it’s not humid outside. If temperatures are high, run the air conditioner with the humidity setting reduced.
- Don’t smoke or allow smoking indoors.
- Dust and clean living spaces regularly.
- Clean up any mold accumulations, and fix water leaks.
- Wash sheets and blankets weekly in hot water.
- Use allergen-proof mattress and pillow covers.
- Control pests by closing up cracks and crevices, sealing leaks, and keeping food covered or put away.
- Change Air Filters Regularly - Central heaters and air conditioners pull air through filters that capture dust and other particulates. Air filters are one of the best lines of defense against the ailments that can arise due to dirty air.
Air filters catch pollutants, particles, bacteria, and other small things that are floating in the air. If you are working to improve your home’s air quality, air filters can help immensely. So, how do you choose the best air filter for your home? Let’s first take a look at the two basic types of air filters:
- Mechanical - Mechanical air filters remove airborne pollutants by capturing them on the filter medium (think of a window screen or a laundry dryer filter).
- Electrical - Electronic air filters use an electric field to attract and trap debris (think of a dirt magnet).
Most homes use mechanical filters because they are the cheaper option. Your home likely has disposable, flat one-inch fiberglass filters that are very affordable, but do little to remove contaminants from the air. Some homeowners upgrade their flat or panel filter with pleated filters (which are more expensive) and provide more surface area to screen out allergy-causing particles.
Still, other homeowners opt for filters in the electrical category, such as a self-contained unit that utilizes an electrical field to trap charged particles. People with severe allergies or who are very concerned about germs can consider a HEPA and/or ultraviolet filter. Filter efficiency depends on a variety of factors, including: filter media (fiberglass, metal, manmade or natural fibers), as well as filter efficiency (fiber density/thickness or number of filter stages). The easiest way to navigate these factors is by using the filter's MERV Rating.
What is MERV?
Every HVAC air filter has a MERV – Minimum efficiency reporting value – rating, which measures how efficiently a filter captures pollutants that pass through your heating and cooling system. MERV measures a filter’s ability to remove large and small airborne particles from the air and assigns a number based on the filter's ability to remove the particles. MERV ratings range from 1 (least efficient) to 16 (extremely efficient). Most home air systems can adequately remove airborne contaminants with a filter rated MERV 8-13. MERV 14-16 is typically found in hospital and general surgery setting. Some studies show that medium-efficiency filters — in the MERV 7 to 12 range — strike the best balance between allergen removal and filter cost. Most residential heating and cooling systems cannot properly function with some of the denser filtration options that can limit airflow and strain the blower fan. In fact, most residential HVAC systems may require modifications for filters greater than MERV 8.
Several types of air filters are common in commercial HVAC systems. These include:
- Fiberglass filters - This throwaway air filter is the most common type. Layered fiberglass fibers are laid over each other to form the filter media and typically are reinforced with a metal grating that supports the fiberglass to prevent failure and collapse.
- Polyester and pleated filters - These filters are similar to fiberglass filters but typically have a higher resistance to airflow and a superior dust-stopping ability.
- HEPA/Ultraviolet filters - High-efficiency particulate air (HEPA) filters are designed to block 99.97 percent of all particles 0.3 micron or larger. Most HEPA filters involve multi-stage sequences to capture smaller particles. Because HEPA units work on the air exchange principle - air is cleaned by continually pulling air from the room into the filtering/cleaning device and exhausting clean air - their effectiveness is determined by calculating the number of air exchanges per hour in a given area. A home can have as many as 67 whole-house air changes a day depending on the house size and HVAC system. The greater the number of air changes in a home, the cleaner the air. Available data indicate that even for very small particles, HEPA filters are not necessarily the preferred option, according to the U.S. Environmental Protection Agency. For these small particles, relatively large decreases in indoor concentrations (around 80 percent) are attainable with medium filter efficiency (such as a MERV rating of 13). Typically, ultraviolet (UV) filters are a built-in component to an electronic air cleaner, or sold as add-ons to a whole-house electronic air filter. The ultraviolet light kills airborne bacteria and viruses, which is why hospitals use UV air filters.
- Washable air filters - These products are not as common and rely on the build-up of dust along the cloth to improve the efficiency of the filter. Industrial processes involving high volumes of coarse dust are typical applications. Because filters are fairly simple — they essentially are porous membranes that allow air to flow through them — little change has occurred to improve problems associated with air pressure drop and its impact on energy efficiency.
- Flat, disposal filters - Standard spun fiberglass filters are designed to protect your HVAC system from large particles of dust. At roughly $1-2 apiece, these basic filters might keep surfaces in your house a bit cleaner, but they can’t block the microscopic particles that are most irritating for allergy or asthma prone members of your household. Most spun filters offer a MERV rating between 1-4.
- Pleated filters - Made from polyester or cotton paper, pleated filters are basically panel filters that have been pleated or folded to provide more surface area. The depth of these pleated or extended surface filters may vary from approximately 1 to 6 inches for medium-efficiency models and 6 to 12 inches for higher efficiency filters. The average pleated filter offers three or four times the amount of surface area of a traditional flat filter. And, as a result, pleated filters can capture smaller, and a greater number, of particles without impeding the airflow of your furnace. Standard pleated filters offer a MERV rating between 5-13.
- Electronic air cleaners (EAC) - Electronic air cleaners use an electrical field to trap charged particles, thereby capturing a higher percentage of pollutants than Flat or Pleated filter media. The dirt and debris removed by the electronic air cleaner are microscopic – less than ten microns. As these microns pass through the intense high voltage electric field, the particles are given an electric charge that draws them to a series of grounded plates that contain an opposite electrical charge. Pollutants are trapped here like a magnet until the collector cells or electrode panel are cleaned. Importantly, as the collection plates/cells become coated with debris, the efficiency of the electronic air cleaner system is reduced. In fact, electronic air cleaners are the only air-filtering device that becomes less efficient as it loads up. Electronic air cleaners do not use a MERV rating.
Efficiency vs. Comfort
A battle exists between HVAC systems that improve efficiency and those that produce a comfortable indoor environment. All filters cause some pressure loss as air flows across the filter media. The longer a filter has been in use, the greater the pressure loss because build-up on the filter media reduces airflow pathways. The increase in pressure loss can increase energy demand because it causes the fans that move air through the system to work harder. Air-filter improvements over the last several years have led to more efficient and less costly filters. The most important design improvements involve placing more folds in the filter media and creating valleys in the media, which increase the filter's surface area and allow air to flow through more effectively.
When it comes to your home air quality, consider a filter type that with an efficient MERV rating (8-16), and make sure you understand what specific problems you’re trying to solve in order to find the right air filter for your needs. Weigh price, reliability, and comfortability factors and you’ll make your home a safer living (breathing) environment in no time.
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