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  1. Air Filters – What are the most important features?

  2. Air Filters – What do they do, what are the different types, and how do they work?

  3. What are good choices for VOG Filters for Maui and Oahu?

  4. What are good choices for VOG Filters for the Big Island?

  5. How do I get my air filter tested?

  6. Where can I find more resources?

1. What are the most important features?

The most important things to look for in an excellent quality air filter are:

The Right Filters – The correct selection and use of appropriate filters and filter media combinations for the existing environmental conditions.

Filter Quality – Highest quality industrial filter materials and filter manufacturing methods.

Large Capacity Filters that are high in volume and weight causing the air to pass through a deep/thick filter media.

Long Lasting Filters that are highly effective over a long period of time.

High CFM rate – allows a large volume of air to be filtered per minute.

Air Tight Filter Housing and Filter Seals so filters work fully without air leaks.

High Efficiency Motor and Fan that are as quiet and energy efficient as possible.

Non Toxic Materials that have no out-gassing

No harmful health side effects such as those caused by ionization and ozone filters.

Automatic filter use monitor, so you know exactly when filters need changing.

Excellent fit, finish and build quality.

Multiple air speeds and remote control.

Readily available filter replacement – filters in stock, and on-island install support.

A reliable filter company with knowledgeable scientists and technical support, an excellent warranty and service agreement.

Support – A knowledgeable Hawaii dealer providing on site testing and monitoring

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2. What do they do, what are the different types, and how do they work?

Air filters can be designed to do many things, but they primarily remove particles, gases or both from the air. Gases are .003 microns and smaller. Ultra-fine particles are .003-.1 microns. Fine particles are .1 -2.5 microns. Course particles are 2.5-10 microns. Vog gases near the volcano are in the sub .003 micron range. Vog particulates tend to be in the .1-.6 micron range. According to the American Lung Association, particulates pose the greatest health risks in the .1 micron range.

There are many types of air filters but the four main types are:

1- Mechanical, 2- Gas Phase, 3- Electronic, and 4- Hybrid

Mechanical Filters – capture particles of different sizes. Three main types of mechanical filters are Flat, Pleated, and HEPA. Flat and Pleated filters are what you see in cars, HVAC, air conditioning systems, and pre-filters, and they filter out large particles. A HEPA (high-efficiency particulate air) filter is by far the best for the removal of dangerous fine and ultra-fine particulates. A true HEPA filter is defined as “a filter having a minimum particle removal efficiency of 99.97% for all particles of 0.3 micron diameter with higher efficiency for both larger and smaller particles.” To qualify as a “true” HEPA, the filter must allow no more than 3 particles out of 10,000 to penetrate the filtration media. Many filters advertized as HEPA or HEPA-style are not, in fact, true HEPA filters and these systems may only remove 50% or less due to poor manufacturing and build quality. The most advanced HEPA filter I have seen is the IQAir Hyper-Hepa filter that filters to .001 microns, which is 300 times smaller than a true HEPA and captures the ultra-fine particles.

Gas Phase Filters – capture different types of gases. Two main types of gas phase capture and control are physical adsorption and absorption (also called chemisorption). Adsorption results from the electrostatic interaction between a molecule of gas or vapor and a surface. Solid adsorbents include activated charcoal, silica gel, activated alumina, zeolites, porous clay minerals, and molecular sieves. Activated carbon captures sulfur dioxide. Chemisorption occurs when a sorbent attracts gas molecules onto the surface of a “sorbent”. Chemisorption involves electron transfer and is essentially a bond-forming chemical reaction between the adsorbing surface and the adsorbed gas molecule. Chemisorbants include potassium permanganate as an active oxidating reagent impregnated into alumina or silica substrates. This chemisorbant will convert a gas like sulfur dioxide, for example, into benign water and carbon dioxide which is desorbed back into the air stream. New technology uses smaller, more active sorbent particles of carbon, permanganate/alumina, or zeolite. These sorbents are manufactured in pellet form, making it possible to create high tech “matrix” gas phase filters which are sorbent mixtures of two or more materials, which more effectively remove specific gases than charcoal or other single sorbents alone. The filters I recommend use this technology.

Electronic Filters – employ an electrical field to charge and collect airborne particles. There are single and double stage electronic filters. The simplest types of single stage filers use permanent static charges in a material to remove particles from the air, where the permanently charged medium acts to both charge and collect airborne particles. A two-stage design uses a high-voltage electrode wire which places a charge on the incoming airborne particles. In the second stage, the charged airborne particles are drawn between a series of oppositely charged metal plates which attract the charged particles from the air, causing them to precipitate onto the metal plates. Another type is the negative ion generator, which use static charges to remove air particles. Unfortunately, negative ion generators operate by charging the particles in a room, which then become attracted to and deposit on people, plants, walls, floors, table tops and curtains where they cause soiling problems. Some units claim to have somewhat reduced the soiling problem by drawing the particles back in to the unit with a fan and on to an electostatically charged sheet. Negative ion generators also have the huge disadvantage of creating ozone.

Hybrid Filters – use two or more of the filter types listed above. There are many combinations available.

Note: Ozone filters are not considered here due to environmental and health risks. According to the American Lung Association: The Federal Trade Commission (FTC) took action against manufacturers of ozone generating devices. The FTC charged that they made unsubstantiated claims about the ability of their products to clean air of various indoor air pollutants and to prevent or relieve allergies, asthma, and other conditions. Under the FTC’s settlements, manufacturers are prohibited from making unsubstantiated marketing claims that ozone is effective in cleaning indoor air, that their products do not create harmful by-products, and that they prevent or provide relief from allergies, asthma, and other specified conditions. Ozone is a potent lung irritant and exposure to elevated levels is a contributor to the exacerbation of lung disease; it is especially dangerous for persons with asthma and other chronic lung diseases, children, and the elderly. Residential indoor ozone is produced directly by ozone generators and indirectly by ion generators and some other electronic air cleaners. There is no difference, despite some manufacturers’ claims, between outdoor ozone and ozone produced by these devices. The American Lung Association does not suggest the use of ozone generators, negative ion generators and some other electronic air cleaners.

In general, a good full spectrum air filter will typically be a hybrid filter using gas and particle filters to suit the environmental conditions.

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3. What are good choices of Vog filters for Maui and Oahu?

For vog, I recommend the following filters for the Hawaiian Islands:

IQAir GC Multigas $1,189.00

For areas up to 900 square feet

Pre Filter: HEPA Class H11

Gas Media Filter: Four 10″ cylinders of Activate Carbon, Impregnated Alumina

Post Filter: Electrostatic Post Filter

IQAir HealthPro Plus $939.00

For areas up to 900 square feet

Pre Filter: Pre-Max

Gas Media Filter: V-F Cell w/ Activate Carbon, Impregnated Alumina

Hepa Filter: HEPA Class H12/13 Hyper -HEPA

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4. What are good choices of Vog filters for the Big Island?

For areas up to 900 square feet

Pre Filter: HEPA Class H11

Gas Media Filter: Four 10″ cylinders of Granulated Impregnated Alumina, Potassium Permanganate

Post Filter: Electrostatic Post Filter

We also have:

Larger filters for larger areas.

Exterior mounted filter systems to save space and eliminate noise.

Whole building filter systems and air conditioning /HVAC integrated systems to filter an entire building.

Safe Room Design including filters, clean air replacement & room design for emergency vog situations.

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5. How do I get my air filter tested?

Air filters have a surprisingly wide range of effectiveness. Some of the brand name filters are largely ineffective as air filters, almost useless as vog filters and poorly constructed where it matters, causing significant air leakage.

Some well known brands add additional harmful pollutants to the building environment due to toxic material choices that out-gas and pollute the air, and dangerous filter technologies that harm the lungs and deposit toxins in the building.

We are beginning a testing program where we will be testing and comparing each filter that we can to determine filter effectiveness. Our test equipment measures air filter input and output air quality to .3 microns using laser particle scanning technology. We will publish the results online.

If you have filters that you would like tested please contact me at (808) 870-2222 or

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6. Where can I find more resources?

Links to air quality and Vog levels:

Environmental monitoring:

Scientists from the U.S. Geological Survey’s (USGS) Hawaiian Volcano Observatory (HVO) at the summit of Kilauea closely monitor the amount and composition of gas emissions from the volcano’s ongoing eruption. Maui has one air monitoring station in Kihei, but no real-time vog monitoring. The Big Island has 7 monitoring stations, and Oahu has 6. A long term goal being discussed with the Dept of Health is to create vog / air monitoring stations on all islands and to create a state wide vog and air quality monitoring network.

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