Whole-House Air Cleaning and Filtration: Many OptionsPublished on: March 7, 2014
You’re likely accustomed to looking at home comfort in terms of how well HVAC systems keep your indoor living areas warm or cool, depending on the season. There is another major area of home comfort, however, that deserves more attention: the quality of indoor air. Some sources suggest that most people spend as much as 90 percent of their time indoors, and that indoor air is often three to five times as polluted as outdoor air. Given these extremes, a program of whole-house air cleaning and filtration will not only make your living areas more comfortable but could also improve your respiratory health and help you feel better overall.
Whole-House Air Cleaning and Filtration: The Basics
Your home contains two main types of pollutants that can reduce indoor air quality.
- Particulates: Particulates are very tiny solid particles of material, such as dust, fibers, metal or wood fragments, pollen, mold, insect parts, dust mites, dead skin cells, and microorganisms such as viruses and bacteria. Particulates can also include liquid droplets or a combination of solid and liquid material. Normal activities of daily living create particulates, even simple acts such as coughing, sneezing or breathing. As the objects around us become worn, microscopic fragments of them break off and enter the air. Other types of activities, such as cleaning, sanding, dusting or sawing, also can create or disrupt particulates.
- Gaseous pollutants: Gaseous pollutants include odors, chemical fumes, smoke, cooking odors, and even material that is intended to improve the air, such as deodorizers. The most dangerous forms of gaseous pollutants are produced by fuel-burning stoves, furnaces and other equipment that can generate exhaust gases such as carbon monoxide.
Whole-house air cleaning and filtration refers to techniques and equipment that will remove or reduce these contaminants while cleaning, filtering and improving the air throughout your home. Whole-house air cleaners, filters and purifiers are usually installed in conjunction with your home heating and cooling equipment. Unlike smaller tabletop or room-level filters and purifiers that clean the air in one small area, whole-house models will improve indoor air quality at every point in your home that’s reached by the HVAC system ductwork.
Your HVAC equipment produces, at base, a large air circulation system. Heated or cooled air is produced by the furnace, air conditioner or heat pump. Air-handling fans push that conditioned air through the supply ductwork and out vents at the ends of the ductwork. Return ducts pull expended air back to be reprocessed and sent out again.
Air filtration usually occurs during the return-air process. In most HVAC systems, return air is forced through a filter made of fiberglass or other filtration media, which captures and holds particulates and airborne contaminants. Usually, the filters used in this process can handle particulates of 0.3 to 10 microns in size, depending on the quality of the filter.
By adding whole-house air cleaning and filtration equipment to the cycle, more contaminants and pollutants are removed from the air circulating through your home. Whole-house systems are either installed directly within the ductwork and airflow of your existing HVAC system, or the airflow is diverted to flow through the cleaning and filtration equipment before returning to its normal pathway. This process allows all of the air that moves through your home heating or cooling system to be processed by the whole-house air cleaning and filtration equipment. Every room or floor that receives heating or cooling will also receive the benefit of air cleaning and filtration.
Types of Whole-House Air Cleaning and Filtration Systems
Standard filtration is a common part of every home forced-air heating and cooling system. This type of filtration uses a flat filter that resembles a cardboard box several inches wide by several inches tall, with a depth around an inch or so. These contain a filter medium made of spun fiberglass, pleated cloth or other material that allows air to flow through it. These filters, especially at the lower range of efficiency, are relatively inexpensive and provide adequate levels of particulate capture.
The efficiency of standard filters are rated by MERV, or Minimum Efficiency Reporting Value. This rating ranges from 1 to 16 for the types of filters that are used in most common HVAC equipment, with the higher numbers indicating better efficiency and improved ability to trap and hold smaller particulates. Keep in mind that higher-MERV filters are usually thick and dense and could interfere with the airflow in your HVAC system, potentially causing malfunctions or damage. Check with your local trusted HVAC professional to see if your furnace or air conditioner can handle high-MERV filter models.
If you need filtration at even higher levels, HEPA, or High Efficiency Particulate Air, filtration systems are available. HEPA filters carry MERV ratings of 17 to 20, and are 99.97 percent effective at capturing and holding very small particulates. HEPA filters will require specialized mounting brackets or fixtures, and are also very thick, which means you will need to make sure they can be used in your HVAC equipment. HEPA filtration is not common in residential applications; it’s used most often in medical, commercial and industrial settings where air quality is of critical importance.
Electronic Air Cleaners
Electronic air cleaners, sometimes called electrostatic air cleaners, use electrostatic attraction to remove particulates from your indoor air. They produce an electrical charge that is transmitted to airborne particles, which causes them to be attracted to surfaces, collecting plates or each other.
- Electrostatic precipitators charge particles as air is pulled through an ionization section. The charged particles are pulled toward metal collection plates, where the charge causes them to adhere and remain in place.
- Ion generators emit charged ions into the air, where they make contact with airborne particles and convey an electrical charge to them. The charged particles then stick to surfaces such as walls, floors, tables or curtains. These types of charged particles can also attach to each other and fall to the floor.
UV Air Purifiers
UV air purifiers, sometimes erroneously called UV filters, use a powerful ultraviolet light to eliminate biological contaminants and microorganisms from your indoor air. They are usually placed within the airflow path of your HVAC system. There, the UV light shines on the airborne contaminants as the air circulates through your furnace or air conditioner. The UV light is a very strong disinfectant, capable of killing germs, bacteria, fungi and viruses. Those microorganisms not killed outright receive irreparable damage to their DNA, making it impossible for them to reproduce. In this way, the UV light system removes potentially harmful, disease-causing microorganisms from your indoor air.
The two most common types of UV light disinfectants are:
- Ultraviolet germicidal irradiation, which is used to treat the entire volume of air flowing through your HVAC system. They are very effective as a supplement to filter-based air purifiers.
- Photocatalytic oxidation, which combines ultraviolet light with a catalyst that reacts to the light. These types of UV systems are not used to remove particulates, but are very effective at getting rid of gaseous pollutants, fumes and odors.
UV lights are often used in commercial locations such as food production facilities, hospitals and manufacturing plants, though they are also becoming more common in residential applications. Remember that UV light is very effective, but it will work only if the light can shine directly on the microorganisms that are being targeted.
Gas-Phase Air Filters
Gas-phase air filtration systems combine a specialized filter media with chemical treatments that remove gaseous pollutants from your indoor air. A substance called a sorbent is used to absorb chemical materials and take them out of the air. Sorbents are usually made of activated charcoal or carbon, and can easily trap and remove gases, vapors, odors and chemical substances. As with most other whole-house air cleaning and filtration equipment, gas-phase units are installed within the standard airflow path of your HVAC system.
Gas-phase filtration relies on two distinct processes:
- Adsorption, which occurs when the molecules of the airborne contaminants are pulled to the surface of the adsorbent material. Adsorption works best at lower temperatures and humidity levels. Remember that some types of adsorption media are better than others at removing specific gases and chemicals; make sure the adsorption material you use will be effective at getting rid of the types of gaseous pollutants you are concerned with.
- Chemisorption involves a chemical reaction between the sorbent or chemicals within the sorbent. This reaction often turns chemical compounds into harmless materials such as water or carbon dioxide, or produces other chemical compounds that will adhere to the sorbent media.
Ozone-Generating Air Cleaners
Some whole-house air cleaners produce ozone gas to help destroy pollutants. These types of systems should be used with caution since ozone is a lung irritant and has been linked to other health problems.
Whole-house air cleaning and filtration will pay off in better indoor comfort, improved air quality, and fewer health-related issues. Contact us today for help finding a contractor in your Southeast U.S. community who can sell, install and maintain air cleaning and filtration systems.