Air Cleaning Systems

Are you concerned about the air quality in your home?  Here is some information on the different types of air cleaning systems to help you breathe easy.

According to the Environmental Protection Agency (EPA), the air inside our home and workplace can be two to five times more polluted than the air we’re breathing outside. Because the majority of us spend approximately ninety percent of our time indoors, it’s important that we ensure the best air quality inside. We want our homes to be safe havens, so how do we eliminate indoor pollution and provide clean air for ourselves, family, and pets?

There are several strategies we can employ to reduce indoor pollutants and improve air quality: source control, ventilation, and air filtration and purification. Once we’ve eliminated known sources of toxic and harmful pollutants in the home, and implemented sound ventilation practices to bring outdoor air indoors, we can start utilizing air filtration and purification. The key to this strategy is filters.

General Filter Facts

Household air filters are available in two different types: media (the material within the filter that removes impurities and pollutants from the air) filters that create a physical barrier, and trap minute particles; and electronic filters, which use a high-voltage charge to attract and capture contaminants. There are a few that combine both methods, and some include activated carbon to fight odor.

Usually, air filters are either connected to your heating, ventilation, and air conditioning (HVAC) system (whole-house filters), or are portable room units with self-contained fans.

Whole-House Filtration Systems

Whole-house filtration systems can be broken down into a few main types:

Filter-based units installed in HVAC furnace systems and air intake points

Duct-based units installed into the air duct path before or after the air handler (a device used to regulate and circulate air as part of the HVAC system) in a central HVAC unit

Stand-alone systems installed into closets or attics, followed by installing additional air intake and exhaust ducts

The most efficient way to filter household air is through your home’s forced-air heating or central air conditioning system. The filters are built into the return-air ductwork, trapping particles as the air passes through. The use of filters to clean air is known as a passive system, and it only works as long as the HVAC fan is running.

Filters come in a range of efficiencies. To determine how efficient a filter is at capturing air contaminant particles, check its MERV (minimum efficiency reporting value) number. The higher the filter’s MERV, the more efficiently it works, meaning the smaller the particle it’s able to capture.

Whole house filters come in four main types:

1. Flat filters. These are found in forced-air furnaces — that matted fiberglass filter that should be changed at least once a month. They’re considered a rudimentary air-filtration system, and are really designed to protect the furnace blower fan from large particles of dust. Once these filters become clogged with dust, they stop working, causing your HVAC system to overwork.

Fiberglass filters will help the quality of your inside air and might keep surfaces in your home a bit cleaner, but they won’t block microscopic particles that are the most irritating to the lungs.

Pleated filters are made of polyester or cotton paper sheets fit more fabric surface into a smaller area. They cost more, and are better at trapping particulates.

The best pleated filters are electrostatically charged to attract pollen, mold, and pet dander. As air passes through the positively-charged outer material it transfers the charge to the particulate matter. This charged particulate matter is then attracted to the negatively-charged inner material, and sticks to it. Smokers, or people with allergies or asthma, may find this to be among the most effective air filter types. However, they can be on the pricey side, and they may overtax your HVAC system if it can’t handle the limited airflow. These filters need to be changed every two to three months.

2. Extended media filters. These boxy units are around eight inches thick, and contain many accordion-like layers of filtration media, making them more effective than fiberglass filters. They can stop bacteria, and are commonly found in medical facilities.

For home use, however, there are a few problems with them. They’re too thick for a standard furnace filter slot, so you’ll have to get a professional to widen the slot. It’s expensive to have them installed and they have to be replaced once a year. As well, their density slows down air flow so much it could damage the furnace blower motor. A professional may be able to help you adjust your motor to handle the greater airflow resistance, or he may suggest a different filter option.

3. Electronic Filters. Sometimes called electrostatic precipitators (ESP’s), these units also have to be installed into the ductwork. These filters remove fine particles from the air by placing an electrical charge on the particles. The particles are then attracted to an oppositely charged collection plate. ESP’s work well on smoke particles too small to be caught by media filters.

Electronic filters never need replacing, but the aluminum collector plates need to be cleaned in soapy water every few months. They’re expensive to install, and require a 120-volt electrical outlet. The problem with ESP’s is that the process of charging particles (ionization) creates trace amounts of ozone, a lung irritant and asthma trigger.

4. Ultraviolet filters. Ultraviolet light zaps bacteria and viruses, and is used by hospitals in tuberculosis wards. Generally UV filters are sold as add-ons to a whole-house electronic precipitator, and are expensive.

Portable Room Air Filters

Portable room air filters are the practical choice if you don’t have central air conditioning or heating. Most portables use HEPA (high efficiency particulate air) filters, which are one of the most effective filters available for the filtration and removal of microscopic particles from the air. Generally, they’re not used in whole-house systems because they need more powerful fans than furnaces can provide.

Ion air cleaners are another type of portable cleaner, and use electrostatic precipitator technology. They send negative ions into the air, charging airborne particles that are attracted to a collection rod (which needs to be cleaned occasionally) in the unit. With some models the charged particles are left in the air, eventually removed by dusting when they fall on room surfaces.

Ion cleaners don’t require fans, are quieter than HEPA units, and are cheaper to run because there are no filters to replace. However, they may produce trace amounts of ozone, which is a lung irritant. Ion air cleaners should not be confused with ozone generators, which use ozone to clean the air and are not recommended by the Environmental Protection Agency or the American Lung Association.

Portable units powered by fans are rated by CADR (clean air delivery rate), which measures both air movement and trapping effectiveness for three types and sizes of particles in indoor air — tobacco smoke, dust, and pollen. The higher the CADR number the more air it filters per minute for that particle size range. Manufacturers recommend that your filter CADR number be at least two-thirds the room’s area in square feet (assuming eight foot ceilings).

Effectiveness of Air Purifiers

While excellent for general air cleaning purposes, some experts do not recommend the use of whole-house air purifiers on a stand-alone basis for people with allergies, asthma, chemical sensitivities or other health concerns. This is because whole-house air purification units rely on your HVAC system to draw the contaminated air from the house and deliver it to the air purifier, and these systems do not always set up a strong enough current to pull large volumes of air from every corner of the house. As a result, the air purifier is unable to clean the air in the entire house to the degree required by those with medical conditions.  Portable air purifiers are much more effective in these cases because they are capable of performing up to eight complete air exchanges per hour within a room, as opposed to the one-half or one air exchange per hour provided by even the best whole-house system.

The ideal solution is to operate a whole-house air purification system in conjunction with room air purifiers. By addressing specific air quality issues first with appropriate portable air purifiers in heavily-used rooms (e.g., bedrooms, living room), the rest of your home can then be easily maintained by the whole-house system.

Quick Reference Chart on Air Purifier Technologies

You’ll find some tips on choosing a portable air cleaner, furnace filter, or HVAC filter for your home from the Environmental Protection Agency here. And the Agency has a technical summary on residential air cleaners here.

Whether you’re considering adding a sunroom or other renovation to your home, call Sunshine Sunrooms at (972) 243-5390 for the very best in design and construction.