Air purifiers and cleaners guide:

This article explains the types of air cleaners or air purifiers used to improve indoor air quality in homes. We include a table of types of air cleaners and the types of particles they handle, comparing their ability to remove materials from the air, their ease of maintenance, and their operating cost.

Air Cleaner / Purifier Types

This article includes excerpts or adaptations from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) , by Steven Bliss, courtesy of Wiley & Sons.

Our page top photo shows that even the naked eye can see comparatively large airborne particles indoors. But many indoor contaminants are simply too small to see, or are not particles at all but rather gases or chemicals.

Table 7-2 Particulate Air Cleaner Comparison

[Click to enlarge any image]

Best Practices Guide to Residential Construction explains:

There are three main types of particulate air cleaners on the market: mechanical filters, electrostatic filters, and ion generators. In addition, there are filters with adsorbents, such as activated carbon, that are capable of removing certain gases (see Table 7-2 above) Most filters are available as standalone units or as add-ons to the home’s HVAC or ventilation system. Some hybrid systems on the market combine two or more strategies, such as a filter to remove particles plus activated carbon to remove odors and organic gases.

Mechanical Filters

These use a matrix of fiberglass or synthetic fibers and resin to filter particles out of air passing through. Some are coated with an oil or adhesive to help trap particles, and others have a static electrical charge. Some types of mechanical filters can be cleaned, but most need to be replaced when full.

As mechanical filters clog, they become more efficient at trapping particles, but airflow is reduced. They can either work in stand-alone units or be incorporated into the HVAC or ventilation system.

• Flat filters 
  
  are the standard fiberglass elements found in furnaces and air handlers. They are designed to catch large dust particles and have little effect on the smaller respirable particles that affect health.
• Pleated filters,
  
  or “extended media” filters, have smaller pores designed to capture small- and medium- sized particles. They are pleated like automobile air filters to provide greater surface area for improved airflow.
  
  Some will fit into a standard furnace filter slot, but the higher-efficiency types are generally too thick and require ductwork modifications. For good performance, they need to be replaced regularly.
• Electrostatic filters 
  
  use a plastic element that is permanently charged with static electricity or captures an electric charge from the passing air.
  
  They are a little more effective than a standard furnace filter at capturing larger particles such as pollen and mold spores, and can be washed and reused when full.
• HEPA 
  
  stands for “high-efficiency particulate accumulator.” These filters range from 95% to over 99% efficient for particles over 0.3 microns, including mold spores, mites, pet dander, and some viruses.
  
  Because of their high resistance to airflow, HEPA filters typically require a separate fan and housing.
  
  Replacement HEPA Filter elements last a year or longer but cost well over $100 versus $10 to $20 for a medium-efficiency pleated filter. Most have a prefilter to catch large particles that would prematurely clog the filter. Prefilters need to be changed regularly.

Electronic (Electrostatic) Air Cleaners

Electronic air cleaners (EACs) use a series of electrically charged metal plates or media filters to pull particles out of the air stream. They are either portable units designed to clean the air in one or two rooms or central systems connected to the return ductwork of the HVAC system.

EAC systems create little resistance to airflow but require a separate fan, which along with the electrical charging device use about 30 to 50 watts of electricity.

Electronic air cleaners are highly efficient at removing both small and large particles, but require more maintenance than many homeowners would like. To remain effective, the filters must be removed regularly and hosed down in a large sink or tub. Some are designed to fit in a dishwasher.

In charging the particles with high voltage, EACs also produce small amounts of ozone, which can be an eye or respiratory irritant at high levels. Most people are not bothered by the amount produced. If this a concern, however, look for a unit with an activated carbon filter to remove the ozone.

Negative Ion Generators to Clean Indoor Air

These work by releasing electrically charged ions, which attach to dust particles in the air causing them to settle on walls, ceilings, furniture, and draperies. Placed too near a wall, they might leave a smudge of particles. Some units contain an optional collector to trap the charged particles in the unit, functioning similarly to an EAC.

Over time, however, the particles can lose their charge and reenter the air. Like EACs, they produce small amounts of ozone. There is little scientific evidence supporting the effectiveness of these units.

Watch out: Do not rely on ozone generators to correct indoor air quality issues, and beware of ion generators that may be adjusted to produce high levels of indoor ozone.

See OZONE AIR PURIFIER WARNINGS and

see OZONE HAZARDS.

Turbulent Flow Precipitators to Clean Indoor Air

The turbulent flow precipitator (TFP) is a new proprietary technology from Canadian-based Nutech Energy System. The device, which attaches to the return ductwork of an HVAC or ventilation system, contains a fan and a labyrinthine core made of aluminum plates and synthetic fibers.

Turbulence in the air flings the suspended particles out of the airstream where they are trapped by a primary and secondary core, which need replacement in one and three years, respectively. Nutech claims that TFPs will capture 99% of particles larger than 5 microns, 97% from 2 to 3 microns, and 90% from 0.5 to 0.9 microns. A TFP unit with HEPA filtration is also available.

Gas Removal Filters to Clean Indoor Air

To remove gases, such as formaldehyde, combustion fumes, or volatile organic compounds, from the air requires the use of special adsorption media. These media contain materials, such as activated carbon or aluminum oxide, which trap the gases in tiny pores.

Different chemical adsorbents are effective with different gases, and none is effective with every gas found in the typical home. Relatively small quantities of activated charcoal can be very effective at reducing odors, but how well they filter out the low levels of multiple chemical compounds typically found in household air is unclear.

In general the rate of adsorption of a gas is reduced as more of the target gas is captured in the filter media. Researchers have also found that, in many cases, some of the gas is reemitted from the filter back into the air. Scientific evidence about the real-life usefulness of these filters in homes is very limited.

-- Adapted with permission from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) .

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2012-11-19 by John - what would be the best solution to clean indoor air if the spore counts for mold is really high?

Hello,

I would like to ask what would be the best solution to clean indoor air if the spore counts for mold is really high? Would hepa filter do the job to remove the mold spores completely along with placing vinegar water in the room to neutralize air?

On 2012-11-20 by (mod) - NO "Solution" - spray or coating - is a substitute for removing the mold and fixing its cause

John,

NO portable air purifier is going to clean air having a really high spore count because you have not removed the spore source. Find and clean upmor remove the mold reservoir.

Otherwise... Think of it like this ... You stand in an upstairs hallway, waving your vacuum cleaner wand in the air wildly 24 hours a day. Do you imagine, for even a moment, that your vacuum cleaner wand, waving around upstairs is going to suck the dust bunnies from under the first floor living room couch?

On 2012-11-21 by Anonymous

Thanks Danjoefriedman! What do you mean by find and clean up or remove mold reservoir ? I mean the area where visible mold was spotted is already taken care of but I just don't know if there's any good home remediations that can be done than paying couple grands for professionals to take care of it.

I found online that I can use certain chemicals or sprays to kill airborne germs and bacterial and was wondering if that can completely remove the mold spores.

On 2012-11-21 by (mod) -

Anon/John:

Yes, if you don't remove the mold reservoir, no amount of "air cleaning" is going to remove a mold problem in a building as you've got what amounts to an infinite particle source.

If a "mold cleanup" has already been performed, if it was a proper and successful job, you won't continue to have high indoor mold spore counts.

In the article links at RECOMMENDED ARTICLES see the article

MOLD EXPERT WHEN TO HIRE for help in deciding if it is justified to bring in a professional.

You can also search InspectApedia for


Do it yourself mold cleanup advice

Finally, and notwithstanding what you saw online, KILLING airborne mold spores is NOT the proper approach to an indoor mold contamination problem. You need to FIND and REMOVE the mold reservoir.

In fact, in quite a few cases, toxic mold spores remain toxic and harmful if inhaled (or gotten in your eye or in a cut) even if they are "dead" - in the sense that "dead" means that the spore won't grow into a new mold colony.

Like any troublesome or costly problem, an indoor mold problem breeds an industry of magic bullets that are appealing but don't work.

If your mold reservoir is less than 30 sqft. you can usually safely clean it up yourself

If you don't know where to find the hidden mold, search InspectApedia for tips on HOW TO FIND HIDDEN MOLD

If you already paid someone to "test" your home for mold, don't hire again someone who just performs a test and does not give you a clue about the size, cause, location, and steps to cure the problem. Otherwise you're not getting much for your money.

On 2012-11-22 by John

I mean everything was removed properly and there's no more visble mold . after mold was removed then i had the IAQ done. results came back with a high count with no visible mold.And the company is recommending me to have them perform remediation to clean the air inside the room. They said opening the window to air out the room would not help to get rid of airborne.

On 2012-11-23 by (mod) -

John,

if the cleanup was correct and complete then there would be no high indoor spore count. Therefore, what we explained before still pertains.

 

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Continue reading at OZONE GENERATOR EFFECTIVENESS for INDOOR AIR POLLUTION or select a topic from the More Reading links just below or see the ARTICLE INDEX.

Or see these

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• AIR FILTER MATERIAL RE-PURPOSED for FACE MASKS
• AIR FILTER OPTIMUM INDOOR
• AIR POLLUTANTS, COMMON INDOOR
• AIR POLLUTANTS, HEALTH EFFECTS
• AIRBORNE PARTICLE SIZE DEFINITIONS & TYPES
• AIRBORNE PARTICLE SIZE TABLE
• ALLERGEN TESTS for BUILDINGS
• ALLERGY & MOLD IAQ PRODUCTS
• BIOLOGICAL POLLUTANTS
• INDOOR AIR QUALITY IMPROVEMENT GUIDE - home
• OZONE GENERATOR EFFECTIVENESS for INDOOR AIR POLLUTION

Suggested citation for this web page

AIR CLEANER PURIFIER TYPES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING INDOOR AIR QUALITY IAQ

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Citations & References

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