When the topic of electronic air cleaners comes up it usually doesn’t take long for questions to arise about ozone and whether it is safe or not. So due to several comments on this blog and questions I have received by email I thought I would share a link to a report I found, published by the US Environmental Protection Agency. The report should provide answers to most questions concerning ozone and any health risks associated with it.

The title of the document is "Ozone Generators that are Sold as Air Cleaners: An Assessment of Effectiveness and Health Consequences"

The topics covered are:

• What is ozone?
• How is ozone harmful?
• Is there such a thing as good ozone and bad ozone?
• Are ozone generators effective in controlling indoor air pollution?
• If I follow manufacturers directions can I be harmed?
• Why is it difficult to control ozone exposure with an ozone generator?
• Can ozone be used in unoccupied spaces?
• What other methods can be used to control indoor air pollution?

http://www.epa.gov/iaq/pdfs/ozone_generator.pdf

The table below is copied from the report for those who do not want to read the document.

Ozone Health Effects and Standards

Question: I am considering replacing my Aprilaire media whole house filter with an electronic filter.  I will be replacing my heat pump within the next few months and would probably buy a Carrier electronic filter.  I am currently using the new upgraded 15 MERV April Air filter. My service technician recently told me that based on his experience, the media high efficiency media filters do a better job of keeping the inside of the air handler cleaner than the electronic filters and the media filters require far less maintenance. He recommended that I continue using the media filter and not replace it with an electronic filter. Your comments are very much appreciated.

I would agree with your service technician 100%. In my experience, electronic air cleaners are over rated. They may be  efficient at stopping smaller dust particles but are not as good at stopping
larger dust particles. For best results use media type filters such as Aprilaire and Nordic Pure.

Dust, pollen, pet dander, mold spores, and dust mite feces are some of the most common things that trigger allergies and set - off allergic reactions in hypersensitive people. Selecting an appropriate replacement air filter for the furnace or air conditioner may help you cope with most of these problematic allergens. In this article we take a look at some of the commonly used filters available.

Fibreglass panel filters are not only the least expensive replacement furnace filters made, they are also the least effective when it comes to removing things that trigger allergies from the air. Fibreglass air filters are constructed simply to catch the largest of airborne dirt and dust particles and they do almost nothing to remove smaller particles like a lot of the most common household allergens. These kinds of air conditioning filters have very low MERV ratings in the 1 to 4 range on the MERV rating chart.

Pleated air filters are an improved variety of panel filter that utilizes pleats or folds in the filter material to increase it’s surface area. This design change makes it much more efficient at trapping dust particles because a much more efficient filtering material can be utilized. Pleated filters are an improvement from disposable fibreglass furnace filters and many are highly recommended for allergy sufferers. The majority of pleated furnace filters will last more than 90 days.

Electrostatic furnace filters are also relatively efficient and affordable. Electrostatic furnace filters are permanent instead of disposable, meaning that you save you money because the best ones last for many years. Electrostatic air conditioner filters eliminate a large percentage of air contaminants.

Electronic filters are permanent, washable filters which rely on electricity to operate. The main benefit is that these filters are long lasting. Several designs claim to remove up to 97 percent of contaminants from the air.

HEPA air filters are probably the most efficient replacement air conditioner filter and can eliminate over Ninety nine percent of your total indoors air-borne pollutants. HEPA filters are frequently utilized in hospitals and also anyplace else that demands the cleanest air possible.

Utilizing top quality replacement furnace filters will safely and effectively enhance the quality of your air. Indoor air is in many cases more than five times more polluted than outdoor air.

MERV stands for Minimum Efficiency Reporting Value and is a measure of how effective the filter is in stopping airborne debris and pollutants. Air filters range from 1 to about 16 MERV.

Airborne allergens are measured in microns. A micron is one 1/25,000 of an inch and a human hair is about 150 microns. The tiniest contaminants which we are able to see are about 10 microns.

Question: I have pleated air filters for my furnace that have a wire meshing on one side. Which way does the filter go in the furnace with regards to airflow direction. With the wire side opposite of airflow or on the same side as the direction of airflow?

Also, for replacement, what Merv value should I use, is it best to find the highest value or is some lower value actually better?

Many pleated air filters have wire mesh on one side of the filter. This wire mesh is used to improve the filters ability to stand up to the forces exerted on it as air passes through it. The longer the filter is in use the dirtier it becomes and more force is exerted on it. If there were no wire mesh the filter may collapse and be sucked out of the filter rack.

Wire mesh is usually found on filters that are made of cotton or some other filter material that is not sturdy enough to withstand the stresses they can encounter in a heating or air conditioning system.

The filter should be installed so that the wire mesh side is toward the fan allowing it to hold the filter material securely in place so that it does not collapse. For more information on this topic read which way do furnace filters go.

Pleated air filters with wire mesh on one side of the filter usually have lower Merv ratings than pleated filters that are sturdy enough to hold their shape without the extra support.

One of the benefits of these filters is that they have less impact on air flow than more efficient pleated filters but you also don’t get the filtering capabilities that the more efficient filters such as Nordic Pure will provide. It’s really a matter of preference. If you want cleaner air use filters with higher Merv ratings. If clean air is not a concern for you then you can use one of the less efficient pleated air filters.

Question: I presently have a Honeywell f100 media filter. Would it be possible to replace it with a HEPA Pure and put a carbon filter with it and use the same housing that the Honeywell f100 currently has?  Will the HEPA pure cause an air flow restriction problem for my home unit?  How often to they need to change in an average home?

Really you have to decide which is more important, using the carbon filter as a secondary filter or using an efficient filter. You can use media filter pads which are decent filters and install carbon pads with them. With media pad filters you will be sacrificing some efficiency but carbon pads are available to use with them.

The Honeywell F100 has a MERV rating of 10 which is quite efficient.
Upgrading to a HEPA filter would increase filtering efficiency. HEPA filters have a MERV rating in the 14 - 15 range which is very high on the MERV scale.

HEPA filters are very efficient and they do restrict air flow. Any system that uses a HEPA filter must have a properly sized duct system and the filter must be maintained properly. If you have not had problems with poor air flow in your air conditioner you could certainly try one. Monitor the system closely for changes in operation. The best thing to do would be to have an HVAC technician check your system to determine if a HEPA filter is advisable. Many contractors don’t recommend using them because of the negative impact on air flow and operating efficiency but for a person dealing with allergies they are often necessary.

Another option is to upgrade to a Nordic Pure pleated filter which has a MERV rating of 12. This is between the one you are currently using and the HEPA filter. More about pleated air filters.

I would not recommend using a secondary filter with the Nordic Pure, the Honeywell F100 or a HEPA filter.