How To Evaluate Allergy Filters
There as been a rising interest in allergyfilters for the home over the last several years.
Once something only purchasedby people with chronic health conditions, more and more people are aware of theneed for cleaner indoor air.
There are several different types of filters thatare marketed by their manufacturers as allergy filters.
Some of these are ofbenefit to those with allergies and some do not.
In this article, we willexploreallergy filters that are installed in the air conditioning or heating system, units that actually attach to the air conditioner or furnace,stand alone allergy filters, ionizers and ozone machines that are marketed asallergy filters, and allergy filters used to filter the fresh air coming intoyour home.
There are several different types of allergyfilters to use in place of your regular filter on your air conditioning orheating unit (HVAC).
This is in place of the current filter you are using on thereturn side of your system.
Most homes use a filter made from a blue, spunpolyester media.
Unfortunately, these trap very few particles and actually haveto be loaded up with dust to start trapping large particles.
A step up from thislevel of filtration is the dry-tack polyester pad.
These disposable allergyfilter pads fit into a permanent frame.
Each change, you remove the old allergyfilter pad and insert a new one.
The pads are usually treated with anantimicrobial to keep mold from growing on them.
The next step up in ability to trap particles isa pleated filter material.
These allergy filters are also disposable and thebetter made ones will last for up to three months at a time.
The idea behind thepleated material to make the allergy filter is that by pleating the fabric youcreate more surface area.
More surface area means more media to trap allergens.
When looking at these filters, you want a MERV rating of 8 or better.
The MERVscale ranges from 1 (least efficient) to 16 (most efficient), and measures afilter's ability to remove particles in the 3 to 10 micron size range.
Thehigher the rating, the more particles removed.
Also, higher rated filters trapmore of the smaller particles.
Last but not least in the HVAC filter category isthe permanent filter.
These allergy filters create an electrostatic charge bythe friction created as air moves across the filtering media.
These filters areusually very high in efficiency (that means they trap many particles) but mayrestrict air flow.
This is true especially for older HVAC equipment.
Once amonth the permanent allergy filter is cleaned with water and reinstalled in theunit.
The next category of allergy filter for the HVACsystem is a whole house HEPA filtration unit thatattaches directly to the HVAC system.
These units can be either HEPA (highefficiency particulate air) or TFP (turbulent flow precipitators).
They work bydrawing a portion of the air (usually about 30%) from the return side andpassing it through the allergy filter and then returning it back into the systemto be either heated or cooled.
These machines allow you to use one allergyfilter to clean all the air in a home.
However, the HVAC system must be on atall times for the air to be filtered.
This may not be an option in parts of thearea where the heating or air conditioning system is not used year-around.
The allergy filter that most people are familiarwith is the stand alone HEPA filter.
HEPA is a measurement.
It means that 99.
97%of particles as small as 0.
3 microns are trapped by the filter.
There are manymakes and models on the market today.
The most important consideration isgetting the proper size allergy filter for the area to be cleaned.
Most allergyfilter manufacturers rate their machines in square footage.
This is not ahelpful measurement, as we live in 3 dimensions and not 2! The first calculation to make is the volume ofair you need to clean.
This is expressed as the cubic feet of air in the room.
Multiply length of the room in feet times the width of the room in feet timesthe height of the ceiling in feet to get the volume of air in cubic feet.
(Length x width x ceiling height = volume).
When you review the differentmakes and models of allergy filters, the most important number is the number ofcubic feet of air moved per minute by the machines motor.
The allergy filter cannever clean any more air than the motor can move.
You use this number todetermine how quickly that machine can clean your volume of air.
For example, ifyou have a larger bedroom that is 12 x 14 with 10 foot ceilings, you have avolume of air of 1,680 cubic feet (12 x 14 x 10 = 1,680).
If you buy a machinethat moves 100 cubic feet of air per minute, than it will take 16.
8 minutes toturn over the air in that room one time.
(1,680 / 100 = 16.
8) That means thatthe air will pass through the filter less than 4 times an hour.
You want aminimum of 6 and ideally at least 8 air exchanges an hour.
In this instance, themachine is sorely undersized and would not be a good buy, no matter what theprice.
It is simply too small for the size of room.
If you have such a largeroom, you would need to either purchase multiple units or look for an allergymachine with more power.
One of the most powerful units on the market is made by AustinAir.
They make several models that move 400 cubic feet of air perminute.
In our previous example, the higher powered machine would result in anair exchange every 4.
2 minutes and over 14 air exchanges an hour.
There are also machines that are marketed asallergy filters that are not truly filters and most certainly are not for peoplewith allergies.
These "allergy filters" are ozone machines and ionizers.
Ozoneunits clean the air by utilizing a third molecule of oxygen as a free radical todestroy odors at their source.
Ozone is not effective in removing particles fromthe air, but it is effective in controlling odors.
Ozone is also a lung irritantand should not be used by people with allergies or asthma.
Many of themanufacturers of ozone producing machines do not disclose this bit ofinformation.
Ionizers are also frequently marketed as allergy filters.
They donot in fact contain a filter.
Ionizers work off the basic principle thatopposite charged particles attract.
Some units work by the use of positive andnegative charged rods.
The particle enters the back of the unit, passes one rodand picks up a charge and then is drawn to the second rod with the oppositecharge.
The problem is once the second rod is covered in particles it no longeremits a strong enough charge to attract any more particles.
The rods must thenbe cleaned, releasing particles back into the air where they are inhaled by theallergic person.
The other type of ionizer uses radio frequency to send bothpositive and negative ions out into the room.
The neutral particles pick upthese charges, then stick to each other, and then fall to the first surface theyhit in clumps.
These machines work great to keep the particles knocked down, butas soon as there is any movement in the room, the particles are disturbed andbecome airborne again.
Many ionizers also produce trace amounts of ozone.
The last type of allergy filter is not atraditional filter, but is a special screen used on your windows.
These screensare called micro air screens and they can trapparticles as small as 8 microns.
These allergy filters fit into your windows andallow you to keep your windows open and bring in fresh outside air withoutbringing in mold, pollen, or other pollution.
So as you can see, there are many types ofallergy filters made today.
Which type of filter you use determines how cleanyour air will be.
Once something only purchasedby people with chronic health conditions, more and more people are aware of theneed for cleaner indoor air.
There are several different types of filters thatare marketed by their manufacturers as allergy filters.
Some of these are ofbenefit to those with allergies and some do not.
In this article, we willexploreallergy filters that are installed in the air conditioning or heating system, units that actually attach to the air conditioner or furnace,stand alone allergy filters, ionizers and ozone machines that are marketed asallergy filters, and allergy filters used to filter the fresh air coming intoyour home.
There are several different types of allergyfilters to use in place of your regular filter on your air conditioning orheating unit (HVAC).
This is in place of the current filter you are using on thereturn side of your system.
Most homes use a filter made from a blue, spunpolyester media.
Unfortunately, these trap very few particles and actually haveto be loaded up with dust to start trapping large particles.
A step up from thislevel of filtration is the dry-tack polyester pad.
These disposable allergyfilter pads fit into a permanent frame.
Each change, you remove the old allergyfilter pad and insert a new one.
The pads are usually treated with anantimicrobial to keep mold from growing on them.
The next step up in ability to trap particles isa pleated filter material.
These allergy filters are also disposable and thebetter made ones will last for up to three months at a time.
The idea behind thepleated material to make the allergy filter is that by pleating the fabric youcreate more surface area.
More surface area means more media to trap allergens.
When looking at these filters, you want a MERV rating of 8 or better.
The MERVscale ranges from 1 (least efficient) to 16 (most efficient), and measures afilter's ability to remove particles in the 3 to 10 micron size range.
Thehigher the rating, the more particles removed.
Also, higher rated filters trapmore of the smaller particles.
Last but not least in the HVAC filter category isthe permanent filter.
These allergy filters create an electrostatic charge bythe friction created as air moves across the filtering media.
These filters areusually very high in efficiency (that means they trap many particles) but mayrestrict air flow.
This is true especially for older HVAC equipment.
Once amonth the permanent allergy filter is cleaned with water and reinstalled in theunit.
The next category of allergy filter for the HVACsystem is a whole house HEPA filtration unit thatattaches directly to the HVAC system.
These units can be either HEPA (highefficiency particulate air) or TFP (turbulent flow precipitators).
They work bydrawing a portion of the air (usually about 30%) from the return side andpassing it through the allergy filter and then returning it back into the systemto be either heated or cooled.
These machines allow you to use one allergyfilter to clean all the air in a home.
However, the HVAC system must be on atall times for the air to be filtered.
This may not be an option in parts of thearea where the heating or air conditioning system is not used year-around.
The allergy filter that most people are familiarwith is the stand alone HEPA filter.
HEPA is a measurement.
It means that 99.
97%of particles as small as 0.
3 microns are trapped by the filter.
There are manymakes and models on the market today.
The most important consideration isgetting the proper size allergy filter for the area to be cleaned.
Most allergyfilter manufacturers rate their machines in square footage.
This is not ahelpful measurement, as we live in 3 dimensions and not 2! The first calculation to make is the volume ofair you need to clean.
This is expressed as the cubic feet of air in the room.
Multiply length of the room in feet times the width of the room in feet timesthe height of the ceiling in feet to get the volume of air in cubic feet.
(Length x width x ceiling height = volume).
When you review the differentmakes and models of allergy filters, the most important number is the number ofcubic feet of air moved per minute by the machines motor.
The allergy filter cannever clean any more air than the motor can move.
You use this number todetermine how quickly that machine can clean your volume of air.
For example, ifyou have a larger bedroom that is 12 x 14 with 10 foot ceilings, you have avolume of air of 1,680 cubic feet (12 x 14 x 10 = 1,680).
If you buy a machinethat moves 100 cubic feet of air per minute, than it will take 16.
8 minutes toturn over the air in that room one time.
(1,680 / 100 = 16.
8) That means thatthe air will pass through the filter less than 4 times an hour.
You want aminimum of 6 and ideally at least 8 air exchanges an hour.
In this instance, themachine is sorely undersized and would not be a good buy, no matter what theprice.
It is simply too small for the size of room.
If you have such a largeroom, you would need to either purchase multiple units or look for an allergymachine with more power.
One of the most powerful units on the market is made by AustinAir.
They make several models that move 400 cubic feet of air perminute.
In our previous example, the higher powered machine would result in anair exchange every 4.
2 minutes and over 14 air exchanges an hour.
There are also machines that are marketed asallergy filters that are not truly filters and most certainly are not for peoplewith allergies.
These "allergy filters" are ozone machines and ionizers.
Ozoneunits clean the air by utilizing a third molecule of oxygen as a free radical todestroy odors at their source.
Ozone is not effective in removing particles fromthe air, but it is effective in controlling odors.
Ozone is also a lung irritantand should not be used by people with allergies or asthma.
Many of themanufacturers of ozone producing machines do not disclose this bit ofinformation.
Ionizers are also frequently marketed as allergy filters.
They donot in fact contain a filter.
Ionizers work off the basic principle thatopposite charged particles attract.
Some units work by the use of positive andnegative charged rods.
The particle enters the back of the unit, passes one rodand picks up a charge and then is drawn to the second rod with the oppositecharge.
The problem is once the second rod is covered in particles it no longeremits a strong enough charge to attract any more particles.
The rods must thenbe cleaned, releasing particles back into the air where they are inhaled by theallergic person.
The other type of ionizer uses radio frequency to send bothpositive and negative ions out into the room.
The neutral particles pick upthese charges, then stick to each other, and then fall to the first surface theyhit in clumps.
These machines work great to keep the particles knocked down, butas soon as there is any movement in the room, the particles are disturbed andbecome airborne again.
Many ionizers also produce trace amounts of ozone.
The last type of allergy filter is not atraditional filter, but is a special screen used on your windows.
These screensare called micro air screens and they can trapparticles as small as 8 microns.
These allergy filters fit into your windows andallow you to keep your windows open and bring in fresh outside air withoutbringing in mold, pollen, or other pollution.
So as you can see, there are many types ofallergy filters made today.
Which type of filter you use determines how cleanyour air will be.
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