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Air Filters — The Ultimate Protection for Your Home’s Indoor Air Quality

Our modern lives differ greatly from those of past generations in many ways. Unlike our ancestors, we spend the majority of our time indoors, in offices, commercial buildings, schools and homes. Because we spend so much time in these enclosed environments, it is increasingly important that we take care of the indoor air quality (IAQ) where we live, work and play. Air filters in our air conditioners, furnaces and other HVAC equipment are the first and most important of the options available to keep indoor air clean and free of particulates and other contaminants. The following brief guide can help you understand the importance of indoor air quality and how to use air filters to keep IAQ at the best possible levels.

The Importance of Indoor Air Quality

Some estimates suggest we spend up to 90 percent of our time indoors, with much of that time spent in the presence of other humans in workplaces, retail establishments, theaters and similar locations. The indoor air quality of these locations can have a significant effect on overall health and comfort. Stuffy, musty or dusty air is difficult to breathe and can trigger allergy and asthma attacks. Poor IAQ can affect overall respiratory health. In many cases, low air quality can contribute to the transmission of communicable diseases.

IAQ inside our homes is particularly important, since we usually spend the greater percentage of our daily hours there. Your home's indoor air can contain both organic and inorganic pollutants that decrease indoor air quality. Inorganic pollutants include solid and liquid particles such as:

  • Dust
  • Mold
  • Pollen
  • Fibers
  • Fragments of wood or metal
  • Powders
  • Liquid droplets

Organic pollutants include contaminants that originate with living creatures, such as the viruses, bacteria, germs and other microorganisms that can spread disease or cause other sorts of physical harm. Animal hair, pet dander, dust mites, mold spores and the waste material of rodents or other animals also fall into this category.

Gaseous pollutants can also cause problems in our indoor environments. These include odors, fumes, smoke, exhaust gases and ozone. Many of the common items we use every day can generate gaseous pollutants. These include paints, household chemicals, cleaning supplies, solvents and pesticides.

When so many of our daily activities are likely to produce an appreciable level of indoor pollution, it's vitally important that we maintain HVAC air filters to help limit the solid and gaseous material that can reduce indoor air quality.

Air Filters: The Basics

Air filters are intended to remove particulates and other contaminants from the air circulating through your HVAC system. Air filters capture and hold these pollutants as the air passes through the filter. The quality of the filter will determine how well contaminants are removed from the air flow.

Heating and cooling systems are designed to maintain a steady of circulation of air between the inside of your home and the furnace, air conditioner or heat pump that provides conditioned air. Supply ducts carry heated or cooled air to the inside of your home or commercial building. Return ductwork pulls expended air back to the HVAC unit. Air filters are installed within this segment of the system, allowing your indoor air to be filtered before it is heated or cooled and distributed again. The air moving through the HVAC unit is literally forced through the material of the filter, where particulates and other contaminants are physically caught and held. Over time, contaminants accumulate within the filters, reducing their effectiveness. Regular filter changes are necessary to maintain fresh indoor air.

Air Filters: MERV Ratings

Air filter effectiveness is most often indicated by the filter's MERV rating. MERV stands for Minimum Efficiency Reporting Value and is an indicator of how effectively a filter can remove particulates of sizes ranging from 0.3 to 10 microns or larger. Standard MERV ratings range from 1 to 16. The higher the MERV rating of a filter, the more effective it will be at removing contaminants.

Air filters usually resemble a wide but thin cardboard box. The frame holds the material where particulates are trapped and held. In medium and low-MERV filters, this filter media is often a type of spun fiberglass or similar material. Some filters are made of pleated cloth, which provides more surface area for the capture of particulates. Other types of filters include material such as activated charcoal that can absorb fumes and odors.

Keep in mind that high-MERV filters can be very thick and dense. These types of filters can interfere with the airflow within your HVAC system, potentially causing malfunctions or breakdowns. Before installing a high-MERV filter, make sure your heating or cooling system is powerful enough to work with a thick filter.

  • Low MERV: Low-MERV air filters with ratings of 1 to 4 are commonly used but only minimally effective. They are inexpensive compared to higher-MERV models, but they are effective at removing only the larger particulates.
  • Medium MERV: Medium-MERV air filters of MERV 5 to 8 are also very common. They work best on particulates of 3 microns or larger and are a reasonably good middle ground between filter cost and effectiveness.
  • High MERV: High-MERV models rated at 9 to 12 provide excellent quality filtration for the money and are appropriate for most residential applications. They are good at removing contaminants of 1 micron or larger.
  • Very high MERV: Very high MERV filters rated at 13 to 16 are the most effective and efficient type of standard filter available. These filters will still fit within most HVAC systems without the need for adapters or special mountings. They work well at trapping small contaminants of 0.3 microns or larger.

Air Filters: HEPA, for When High-MERV Isn't Enough

In some cases, you may need a filtration system that provides even higher levels of air cleaning and particulate removal. If so, you can consider installing a HEPA (High Efficiency Particulate Air) filter. These filters work at MERV levels of 17 to 20, and are up to 99.97 percent effective at removing contaminants.

HEPA filtration systems are usually not used in residential settings. They are most common in commercial and industrial environments where air quality cannot be compromised and indoor air must be kept as clean as possible. This includes medical facilities, computer clean rooms and electronics manufacturers. HEPA filtration is usually called for in homes only when a resident has a medical condition that demands the cleanest indoor air possible.

Like other high-MERV filters, HEPA models can interfere with system airflow. They will also require specialized mountings or adapters before being installed. HEPA filtration systems are often separate units installed within the airflow of your HVAC system.

Air Filters: Why Change Them?

As important as air filters are, it is equally important to remember to change them regularly. Over time, filters can become clogged with the particulates they're pulling from your indoor air. As filters become dirtier, they become less effective at removing particulates, which means your indoor air quality will decrease.

Dirty air filters are also a major source of HVAC system malfunctions and breakdowns. The blockage they create in system airflow can cause significant problems with your heating and cooling equipment.

Some of the more significant issues you may encounter from dirty air filters include:

  • Decreased HVAC system effectiveness and efficiency: The performance of your furnace or air conditioner can drop substantially when air filters are dirty. This can result in inconsistent heating or cooling, extra wear and tear on HVAC equipment, and excess use of energy.
  • Increased heating and cooling costs: Inefficient HVAC equipment must run more often to make up for losses of heating and cooling, which can significantly increase your monthly home comfort expenses.
  • Damage to HVAC equipment: Fans and air handlers must work harder to move air through your HVAC system if the filter is dirty. This can cause damage to these components or cause them to wear out sooner than they should. Damage and malfunctions can increase overall home comfort expenses by increasing the number and frequency of equipment repairs.
  • Harm to the environment: When your HVAC equipment works harder, it consumes more energy to maintain indoor temperature settings. This increases requirements on local utility companies to produce energy. As power plants use more fossil fuels to generate electricity, additional levels of outdoor air pollutants are generated.

In general, filters should be checked once a month and changed if they are dirty. If your HVAC system is operating frequently or if your indoor air tends to have a large amount of particulates in it, you may need to check and change filters more often. Fresh filters should be installed whenever you have preventive maintenance performed or your furnace or air conditioner.

Comfort24-7 serves HVAC customers in northwestern Indiana, southwestern Michigan, and the Chicago area. Contact us today for more information on HVAC system air filters and the role they play in preserving your indoor air quality, or for expert assistance finding the type of air filters that will work best for your home or commercial establishment.

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