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A Guide to Home Air Purifiers

By Benjamin Hardy
6/12/2013 9:02:12 AM

What to Clean

Air impurity is caused by two general pollutants: particulates and gasses. Within the first category there are a number of culprits, including organic and inorganic compounds, bacteria and viruses. Smoke, dust mites (and their feces), insect parts, pollen, dander and particles generated from organisms like mold and fungal spores all fall into the particulate pollutant category. These allergens are inhaled, can become deeply imbedded in the respiratory system and can even be absorbed by the bloodstream. Mechanical air filters, air cleaners and products designed for pollutant destruction can be used to address air quality issues associated with particulate pollution.

The off-gassing caused by products and materials in the home has become an important topic to address for homeowners and homebuilders exploring their "green" options. Alternative green products designed and manufactured to reduce or eliminate harmful off-gassing are marketed to those for whom indoor air quality (IAQ) is of great concern. Many green home certifications require minimum IAQ standards, and green home educational courses often list IAQ as a key curriculum topic.

The ECO10 from Blueair. Credit: RenovateYourWorld

Even in the "green" home, however, gaseous pollutants can be a concern. Gaseous pollutants can include gases released as a result of combustion (nitrogen oxide, carbon monoxide and nitrogen dioxide are a few) usually associated with appliances like gas stoves and heating systems. Off-gassing products can include furniture, carpets and paints and varnishes that release chemicals into the air over time. The volatile organic compounds (VOCs) often mentioned in green home literature fall into the gaseous pollutant category. Even cleaning supplies and personal hygiene products can contribute to gaseous pollution in the home.

Unpleasant odors may not necessarily have an adverse effect on one's health, but they can still be a nuisance. Some air purifiers and cleaners include features meant to reduce or eliminate foul odors caused by smoking and cooking.

How to Clean Your Air

There are a few ways to clean the home's air of its many potential pollutants. Here are the types of air cleaners available on the market.

Air filter solutions trap particulates as air passes through the filters. Filter systems can be found in whole-home HVAC solutions or portable single-room solutions. Filtered systems are given a minimum efficiency reporting value (MERV) of 1 to20, with 20 being the highest (and best) rating. Low-MERV filters are common in HVAC systems but are only effective at preventing the buildup of large particulates on the system's fan or elements. Filters in the 17 to20 MERV rating are considered high-efficiency particulate air (HEPA) filters and must pass a test to be given the HEPA label. These filters trap a minimum 97.7 percent of particles of .3 microns. In other words, these filters are very effective at trapping a very high percentage of very small particulates.

Activated carbon air filters, sometimes known as gas phase air filters, are used to eliminate gases and odors from the air. These systems will use a sorbent-such as activated carbon-to absorb gases and odors associated with smoking and off-gassing materials. Activated carbon filters are not useful for particulate reduction but will complement such a system.

Ultraviolet germicidal irradiation (UVGI) systems or germicidal UV lamps use UV light to kill gaseous pollutants like bacteria, viruses and fungal spores that are airborne or on surfaces like ductwork. These systems can also eliminate odors, but they will not filter particulates.

Photocatalytic oxidation (PCO) is another method of purifying the air of gaseous pollutants. These systems use a UV light in conjunction with a catalyst substance to eliminate gaseous pollutants by degrading or oxidizing them.

Air ionizers remove particles from the air by releasing negative ions, which changes the polarity of airborne particulates. The charged particles then become attracted to one another and fall from the air or "stick" to walls and other surfaces. Some air ionizers have collector plates that electrostatically attract the charged particles.

Ozone generators release ozone into the air, which is an oxidant that will eliminate bacteria, chemicals and odors. These devices have come under scrutiny as ozone in high concentration is an irritant and unhealthy, and, while effective at battling odor, are not useful for particulate reduction.

Multi-function or hybrid models are becoming more prevalent on the market; these products acknowledge the many causes of poor indoor air quality and are designed to eliminate multiple pollutants with one unit. The Blueair product line uses their patented HEPASilent filter system, a combination ionizer and electrostatic filter, to purifier the air. Their latest ECO10 is an environmentally friendly unit that runs on very little electricity. "The ECO10 is the world's most eco-friendly purifier," says Blueair spokesperson Nicole Vance. "It runs on 10 watts of electricity."

Product Application: Whole Home vs. Portable

Generally speaking, air purifiers and cleaners fall into one of two application categories: whole-home (sometimes called in-duct or central filtration units) and portable. Whole-home systems are used in conjunction with the home's central air (HVAC) system or forced air heating system. Air filter systems are commonly used in whole-home application, and UV light solutions like UVGI and photocatalytic oxidation can be installed to keep the ductwork and other HVAC surfaces free from viruses, bacteria, mold and other allergens. With most central filtration units, the system's fan has to stay on in order for air to be circulated and cleaned.

The portable air cleaner or purifier is often the more affordable and effective solution to improving indoor air quality. Mechanical (fan-driven) air filters, activated carbon filters, air ionizers, UVGI and PCO, and ozone generators are all found in portable designs. Sizes and costs will vary depending on product type and manufacturer. The ratings for portable systems will vary, but consumers should look for the clean air delivery rate (CADR), which was put in place by the Association of Home Appliance Manufacturers. The CADR rating measures the products delivery of clean air in cubic feet per minute. When purchasing an air cleaner, look for three CADR numbers: one for tobacco smoke, one for pollen and one for dust. The higher the number, the faster the unit filters the air.

Cost and Other Considerations

While the upfront cost of any air purifier or cleaner is always the first consideration, consumers are advised to evaluate all the costs associated with installing, operating and maintaining a system. Whole-home or in-duct systems will often require professional installation, which comes at a price as well. The IQAir Perfect 16 Whole House Air Purification system for a 3-ton HVAC system, as an example, costs $2,795 for the product and the install. The IQAir units must be installed by qualified, professional installers, which can be found on their Web site by entering one's ZIP code.

Portable units almost always plug into an outlet, so electricity costs should therefore be considered. Other costs incurred for replacement filters, bulbs and moving parts should be explored prior to purchase. "Our SAP 1000 has a lamp that is good for 9,000 hours and costs only $48 to replace," says Jeannie Mitchell, co-founder of Better Living of Arkansas and makers of the Sun Aire Line of products. The SAP 1000, retailing at $650, is their residential air purifier unit, which uses dual-frequency UVC technology to kill gaseous pollutants and odors. "Our washable pre-filter works to .5 microns and saves a homeowner around $200 on replacement filters" adds Mitchell.

Consumers will also want to evaluate the noise of the running unit. For any unit to be effective, it should be operating 24/7. Operating sound should be listed on product packaging and measured in decibels (dB).

It's not possible for one individual to control the air quality outdoors; controlling it indoors is another matter. With an air purifier or cleaner available for nearly every indoor air pollutant, it's a common sense decision for a homeowner to take the necessary steps towards ensuring a clean and healthy home air environment.

Text by Benjamin Hardy

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