February 22nd, 2010 — Filter QA
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
| Health Effects |
Risk Factors |
Health Standards |
Potential risk of
experiencing:
|
Factors expected to
increase risk and
severity of health
effects are: |
The Food and Drug Administration (FDA)
requires ozone output of indoor medical devices to
be no more than 0.05 ppm. |
Decreases in lung
function
|
Increase in ozone air
concentration |
The Occupational Safety and Health Administration (OSHA) requires that workers not be exposed to an average concentration of more than 0.10 ppm for 8 hours. |
| Aggravation of asthma |
Greater duration of
exposure for some health effects |
The National Institute of Occupational Safety and Health (NIOSH) recommends an upper limit of 0.10 ppm, not to be exceeded at any time. |
Throat irritation and
cough |
Activities that raise the
breathing rate (e.g.,exercise)
|
The Environmental Protection Agency (EPA)’s National Ambient Air Quality Standard for ozone is a maximum 8 hour average outdoor concentration
of 0.08 ppm. |
Chest pain and shortness
of breath |
Certain pre-existing lung
diseases (e.g., asthma) |
|
Inflammation of lung
tissue |
|
|
Higher susceptibility to
respiratory infection |
|
ppm = parts per million |
April 5th, 2009 — Air Filters
Ozone (O3) is a 3-atom form of oxygen and is a normal trace element in our atmosphere. Ozone is a different chemical than common oxygen (O2) which supports life. Like many substances, ozone is beneficial to life but can also be harmful in excessive concentrations.
Like many household appliances, electronic air cleaners produce ozone when they operate. The amount of ozone produced varies among models.
Ozone is formed when an electric discharge passes through the air and there are many natural sources of ozone. For example, ozone is formed naturally by lightning and is also formed as a by-product of some electric motors and appliances. Ozone is created by air passing through an electrically charged field.
How electronic air cleaners work
Small particles of dust pass through the charging section of the air cleaner and receive a positive electrical charge from a series of tungsten wires. These charged particles then pass by the negatively charged collector plates, which attracts them like a magnet. The particles remain on the collector plates until they are washed away during periodic cleaning of the collector cells.
Can you smell the ozone produced by the electronic air cleaner?
Sensitivity to the smell of ozone varies quite a bit among people. Some people can smell levels at .02 ppm but most people notice the smell of ozone at .03 ppm which is well below the FDA standard. The smell of ozone is not an indicator that the level is above normal, or even near the recommended limit set by the FDA.
Do electronic air cleaners work?
Electronic air cleaners do work. But like all air cleaners and air filters they have their positive and negative characteristics. Many people are very satisfied with their performance and would recommend them to anyone.
February 22nd, 2009 — Filter QA
Question: I have a Honeywell electronic furnace filter on my furnace. The power panel failed and the unit is very expensive to replace. However, I can install pleated air filters in place of the original electronic cells. The filter size is 20 X 25 X 4 inches thick. As a temporary measure, I have installed 3-1 inch thick MERV 8 air filters in parallel into the filter opening. How does the MERV rating change when the filters are placed in parallel? Is what I have done a good solution? If not, what would you recommend that I do?
I would remove two of those 1 inch pleated air filters ASAP. Installing filters in this way has a very negative effect on air flow and reduces equipment efficiency greatly. Take a look at your air handler to see if there is a place to install a 1″ filter. Most air handlers come equipped with this filter rack.
Take a look at the pictures on this page “where is my furnace filter” if you are not sure where to look. If you can’t find a place to install a 1″ filter, you can get a 20 X25 X4 MERV 12 filter at NordicPure for a very reasonable price.
November 26th, 2008 — Filter QA
Question: I have a whole house electric AC with gas heat in my home, which is approximately 1800 sq ft. There are 2 return air grills with filter in the house and a filter tray at the bottom of my furnace in the return air system.
The sizes are as follows:
Grill #1 is 20×20x1
Grill #2 is 20×24x1
The under furnace tray is 24×24x1
What filter combination should I run? Filter in all 3? And what type. I’m looking for the best airflow (low pressure drop) with the most filtration.
If you are looking for the best combination of air flow and filtration I would recommend a pleated filter with a relatively high MERV rating 10 - 12 and change it monthly. Although filters with higher MERV ratings have more pressure drop than air filters with lower MERV ratings, they will provide the best filtration. Change the filter monthly to prevent the air flow from being effected greatly.
Stacking filters is not a good idea because combined they may cause excessive pressure drop and can be far worse than having one pleated air filter with a high MERV rating. I would remove the filters from the return air grills.
If you are interested in upgrading your system, you can install an electronic air cleaner and install a pleated air filter as a pre-filter. Electronic air cleaners have almost no effect on air flow. Remove the foam pre-filter that comes with the electronic air cleaner and use a pleated filter instead. This combination will provide the best filtration and the least pressure drop.
