All You Ever
Wanted to know about AC Filters.
WHY FILTER THE AIR? :
The average human
breathes about 16,000 quarts of air each day. each quart of air we breathe has about 70,000 visible and invisible particles.
The U.S. Environmental Protection Agency (EPA) notes that indoor air is often more polluted (five to ten-times more and occasionally
100-times more) than outdoor air. Today, more than 50 million Americans suffer from allergy and asthma problems caused by
pollen, dust, mold spores, pet dander, mildew and gases that circulate in the home. Most of the pollen, mold, dust and particles
people breathe into their lungs is approximately three microns or smaller - much less than the size of a human hair.
Good
indoor air quality (IAQ) depends on a number of factors, including effective filtration, which provides the primary defense
for homeowners and HVAC equipment against particular pollutants.
Your heating and air conditioning system is most efficient
when the airflow is at its peak. Simply put, if your A/C coil or ductwork is clogged, the airflow is diminished. That means
the system must run longer to heat (or cool) the same amount of space. If you filter the air as it enters the system, your
equipment won't get clogged up. If you neglect the filter long enough, the A/C coil will get so clogged that the air conditioning
evaporator coil will freeze into a solid block of ice. To repair this will require a service technician to take the system
apart and clean it and a fat wallet.
You take pride in your home. You vacuum, you dust the furniture, you clean the walls.
Now look up at the ceiling! Where did that ugly black film around the supply air registers come from? In an older home it
can be a sign of dirty air ducts caused by using an inefficient air filter. No matter what the cause, it is dirt, smoke, pollen,
and dust that was not caught by the filter. You can wash it off but it will come back.
AIR POLLUTANTS:
Air pollutants
are; dust, pollen, dust mite remains, mold spores, animal dander (mold food), smoke, bacteria, and viruses. Of all the above,
Pollen and Mold Spores are constantly being brought in the home on your clothes and hair. Dust Mite remains, Smoke and Animal
Dander (skin flakes and hair) serve as food for mold and are also allergens. In general, any airborne organic matter is mold
food.
A LITTLE BIT ON THE SUBJECT OF MOLD:
Mold requires three things
to survive: appropriate temperatures, food, and moisture. Mold is a plant that lacks chlorophyll and therefore cannot produce
it's own food. It must trap airborne organic matter and ingest it. One of the most important components of control is the
limitation of moisture in the environment and in the HVAC system. Indoor spaces must have a controlled humidity level of less
than 60% for mold free environments.
Once mold gets in your HVAC system it will reproduce at a rate of up to 33 million
plants in a 24-hour period. It reproduces by releasing spores into the air. Mold spores are within the 1 to 10 micron size.
That's about one-fiftieth the width of human hair.
These spores are somewhat like seeds of a plant and will grab a foothold
in the system or the ductwork if allowed to. These spores must be trapped as they pass by in the air in order to control the
mold. A good quality filter will do just that. And, the more spores captured, the less probability that mold will grow.
TYPES OF FILTERS:
1. Disposable air filters:
The most
common is the standard fiberglass media filter with a cardboard frame.It looks like blue cotton candy in a box. If you hold
it up to a light you can see right through it. This type of filter will cost you about $1.00 US if you get it from your local
grocery or hardware store. You just install it in your furnace or filter grill and throw the old filter away. They are not
very efficient but they do offer some protection to keep your air conditioning coil from getting clogged up. They only remove
the large particles of dust. While better than nothing, they are not a lot better.
The most simple way to demonstrate
this is to pour a handful of fine dirt or pepper on to the filter and watch how much falls through it.
These type of filters
will only remove approximately 10 - 15% of the dust in the air. That means that about 85 - 90% of the dirt, dust, pollen,
and other air born pollutants will pass through the filter and either become lodged in the evaporator coil (which over time
can and will cause the air conditioner and furnace to run inefficiently, increasing electrical and gas consumption ), or put
the contaminants back into the air stream for us to breath. Breathing airborne pollutants often triggers allergy, asthma,
and hayfever symptoms.
2. Hog Hair
Hog hair filters falls under the category of washable
air filters. They somewhat resemble a flattened bundle of plastic coated thread. The main ( and only) advantage to them is
that they can be washed.
* No more trips to the store to get a new disposable filter.
* They have a life span of two
to three years.
* Hog hair filters are pretty inexpensive too. They cost about $5.00 - $10.00.
But,
* They are
not very efficient.
* Hog hair filters only capture 10 - 15% of the particles in the air. As above, better than nothing.
3. Wire mesh
If you have an exhaust hood over your cooking range you have probably seen
a wire mesh filter. You probably call it a grease screen. The heating and air conditioning version is just bigger. It
is more efficient than the hog hair filter (not much though) and they tend to last a little longer. The wire mesh filter can
capture about 15 - 25% of the particles in the air.
One problem with them is that the frame is easy to bend and the media
can get snagged on things when removing it to clean. Once the media has bunched to one area it is very hard to return it to
it's original shape.
4. Electronic
Before the advent of
Electrostatic Air filters the Electronic air filters were the best type of filter available to the general public. They require
household current to operate. In general they work as follows:
* 110 Volts AC is stepped up to about 5,000 Volts DC.
*
This high voltage is transmitted to electrodes inside the filter grid as air is forced across it.
* Particles of dust
will "short" across the electrodes causing an arc of electricity that gives the particles a static or positive charge.
*
Electrodes further inside the filter are charged with an opposite or negative static charge.
* In electricity as well
as magnetism opposites attract and the positively charged dust particles are attracted to and stick on the negatively charged
electrodes.
* The filter is periodically cleaned with soap and water to remove what it has collected.
Electronic air
cleaners can be quite efficient (70 - 90%) but they do have a downside.
* First, they are noisy. They sound like a bug
zapper and this goes on as long as the system is running. Many people find this to be quite annoying. However if the air handler
is in the garage it will not be annoying.
* Second, they tend to loose efficiency as they get older.
* Third, they
are a bit expensive to buy and if they break (for example during cleaning) you must pay to have them repaired (if it is fixable).
* And finally, you need a qualified professional to install or service them.
5. Electrostatic
Air filter
An electrostatic Air Filter is very efficient. It removes up to 95.3% of airborne particles.An electrostatic
filter uses electrostatically charged polypropylene and polyurethane filtration medias to attract particles as small as .3
micron. (1 micron = 1/25,000 in.). A safe static charge is produced by forcing air across the filter. This static charge attracts
and traps airborne particles into the filter just like a magnet. Simply clean the electrostatic filter every 3 - 4 weeks with
mild soap and water.
WHAT FILTERS DO:
A
"good" filter can remove dust, pollen, dust mite remains (mold food and an allergen), mold spores, animal dander (mold food),
smoke, bacteria, and some filters even viruses and smells. A "good" filter is one that has the ability to trap 80% or more
of the above particles. All of these particles are "microns" in size. A micron is one millionth of a meter or about 1/30,000
of an inch. As an example, human hair is 70 microns thick. The following table gives you the size ranges of the above particles:
PARTICLE
TYPE SIZE RANGE (microns)
Pollen
10 - 100
Mold Spores 1
- 50
Bacteria
.5 - 5
Pet Dander (mold food) .1 - 10
Dust
.01 - 100
Smoke
.01 - 1
Virus
.003 - .5
Most filters are rated in MERV. MERV stands for Minimum Efficiency Reporting Value. A higher MERV indicated
better performance. A MERV 13 filter with six air changes per hour would have an approximate 100% efficiency in capturing
molds. The higher end of most "off the shelf" filters is MERV 11. An electrostatic MERV 11 filter will be more than ample
to remove 90 - 95% of the pollutants with the exception of Smoke, Viruses, and some bacteria (98% of all bacteria known to
man are over 1 micron in size and thus trapped by a MERV 11 filter). As an Example, 3M Corporation sells the "Filtrete" electrostatic
MERV 11 filter in various sizes within a range of $5 to $9 dollars each (try Home Depot, ACE hardware, or Loews and your local
Supermarket). It is a white accordian-pleated filter.. These are 3-month filters so it is well worth the money to insure a
clean indoor environment.
The following table lists the sizes for various mold spores and the filter MERV rating
needed
to trap it:
Mold/Fungi
Diameter Filter Selection
(microns) (MERV)
Phialophora spp.
1.5 13
Exophiala jeanselmei
2.0 13
Anthrax
2 - 5 11
Geomyces pannorum
3 7
Histoplasma capsulatum
3 7
Paecilomyces variotii
3 7
Wallemia sebi 3
7
Emericella nidulans
3.3 7
Penicillium spp.
3.3 7
Phoma
spp.
3.3 7
Aspergillus
spp.
3.5 6
Absidia corymbifera
3.8 6
Coccidioides immitis
4 6
Trichoderma spp.
4.1 6
Aureobasidium pullulans
5 6
Chaetomium globosum
5.5 6
Cryptococcus neoformans
5.5 6
Stachybotrys
spp.
5.7 6
Eurotium spp.
5.8 6
Scopulariopsis spp.
6 6
Sporothrix schenckii
6.5 6
Botrytis cinera
7 6
Mucor
plumbeus
7.5 6
Rhizopus stolonifer
8 6
Cladosporium
spp.
9 6
Hetminthosporium
12.5 6
Blastomyces
dermatiitidis 14 6
Rhodoturula spp.
14 6
Alternaria alternata
14.4 6
Ulociadium spp.
15 6
Epicoccum nigrum
20 6
Paracoccidioides
brasilensis 23 6
The molds in bold represent the notorious "Black or Toxic
Molds". A MERV 13 filter will trap all mold spores. With the exception of the first three types of mold, a MERV 11 filter
will trap 92% of all other types of mold including Anthrax and the Black Molds.
WHAT FILTERS DON'T DO:
Filters
will do nothing if there is no airflow through the system. Air must be moved through the filter in order for it to remove
mold spores and other contaminants. It is recommended that the HVAC system should be able to recycle the house air volume
six times in an hour in order to have peak air cleansing performance.
No matter what kind of filter you get it will be
worthless if there are leaks in the system at any point past the filter (we'll talk about the resolution in another flyer).
THE WORST FILTER TO HAVE IS PROBABLY
THE ONE YOU HAVE:
Most HVAC systems are installed with a manufacturer's or Low-efficiency filters. They are typically
used to keep lint and large particles from clogging the heating and cooling coils of an HVAC system. If you take it out it
will have a blue color and be pretty much see-thru when put up to the Sun. They do nothing for your indoor air quality (try
pouring pepper or salt on them and watch it drop right through).
PROPER HVAC AIR FLOW:
Your
HVAC system should be able to recycle the house air volume six times in an hour. If your AC Company is reputable, it installed
the proper size system and you don't have to worry. They usually try to sell you 1/2 to 1 ton more than you need so it should
be OK. A rough rule of thumb is to take your home's area in square feet and divide it by 500. That number should be the number
of tons your HVAC system is rated for plus or minus 1/2 ton. As an example, a 1,000 square foot home has a volume of approximately
7,000 cubic feet (7 foot ceilings). Therefore the system must recycle 42,000 cubic feet per hour (7,000 times 6). A typical
HVAC system is designed to move 400 Cubic Feet per Minute (CFM) per ton. Each ton of an HVAC system will efficiently cool/heat
400 - 600 feet of your home. So a 1,000 square foot home would have a minimum of a 2-ton system installed. That's 800
cubic feet per minute times 60 minutes or 48,000 cubic feet per hour (more than 6 times the volume needed shown above).
WHAT FILTERS TO USE:
You should think of a filter as preventative maintenance
equipment. If you do not have a mold problem initially, the right filter will prevent any future growth. Good filters will
clean the indoor air and remove a very high percentage of spores but remember that a filter is not the magic cure all. Other
things must be done if infestation is high (we'll discuss this later). The good news is even a MERV 6 pleated filter will
remove 80% of the mold spores passing thru it
PROPER REPLACEMENT
TIMES:
Most manufactures will tell you when to replace the filter (i.e. every month, 3 months, etc.). It
is absolutely necessary that you do so. You must remember that all manufacturers recommended replacement times are based on
perfect indoor conditions. If you have pets, smoke, or burn candles a lot the replacement time should be approximately half
the manufacturer recommended. Dirty air filters themselves can provide a breeding ground for mold and mildew. A clogged filter
will slow down the airflow to the system and can create expensive problems in your HVAC system if left dirty. On the contrary,
the efficiency of filters generally increases as they trap particles (a three month filter is most efficient at approximately
2 months then when first installed).
HELPFUL HINTS TO REDUCE
POLLEN AND MOLD IN YOUR HOME:
Keep the HVAC fan on 24 hrs. in the spring and fall to keep air moving to remove mold
spores. These seasons are the periods noted for high pollen and spore counts.
SHOULD YOU CLEAN YOUR
SYSTEM? :
Unfortunately, an HVAC system can present optimum temperatures for growth of most molds. "For some,
80 to 95 degrees is excellent. Others can proliferate at the same temperature ranges that we find comfortable. When we have
dark areas and crevices, system contaminants that supply nutrients, and moisture, we have an excellent breeding ground for
mold. Therefore, besides keeping humidity under control, a good rule of HVAC operation is: Keep it clean." Look up at your
AC vents. Do they have black round spots on them? Are there any dark lines on the ceiling coming from the vents? Is there
a musty smell in your home? If so, you need to call a professional and have your ducts and inside your Air Handler Cleaned.
HVAC is a closed loop system so you need both to be cleaned. Otherwise one will recirculate back into the other and you've
thrown your money away. Also ask if the price includes a mold remediation treatment and a microbiocide treatment.
IF I FOLLOW THESE
HINTS WHAT WILL I SAVE? :
My other business (The Environmental Air Force) is prosperous because I clean ducts
and remediate mold. It has been my experience that the majority of homeowners needing duct cleaning needed it because they
either had manufacturer's filters or didn't change the filters. In addition, I work with AC Contractors daily and the number
one reason systems fail to operate properly is due to excessively dirty filters. By maintaining clean, efficient filters you
won't need two or more service calls a year and you won't need a duct cleaning, Mold remediation, and Air Handler cleaning.
The average "no air" service call runs between $125 and $200. The average Duct Cleaning Service costs $400-$700. The average
mold remediation and microboicide treatments cost $175. The average Air Handler Cleaning (blower pull and clean, evaporator
coil clean, and condensate pan and drain clean will cost $400. So you will probably save between $1,225 and $1,675 just by
keeping the system clean. Plus the added feature of clean, mold, pollen, dust mite free air. We hope that makes you breathe
easy!
