There are several good choices for consumers existing in today’s marketplace. Your choices of air purifier may be completely different based according to what you are trying to achieve in your particular indoor air quality situation. For instance, if your main goal is to clear your air of allergens, you should choose an air purifier which would remove the large particulate matter such as pollen or dust with a pre-filter, but also the smaller allergens, ie: particulates from 0.3 to 5 microns in size. These smaller allergens include mold, bacteria, various animal danders, fumes (volatile organinc compounds: VOC’s) and house dust mite allergens among other things. The Best Air Purifiers would trap this size of particulate matter and remove that contamination from your room’s air. However, it is important to know that more than 90% of all particulate matter are 0.3 microns or less in size. These particulates are known as “lung penetrating particles” and are thus most dangerous to your health. Particulate matter of this smaller size, include viruses, some bacteria and germs, some house dust mite allergens, animal allergens, cigar and cigarette smoke, soot, fumes, and smog.
Since most standard Hepa filters would not be able to trap most of these smaller particles, there are also some machines that utilize ultraviolet light in combination or as a standard alone machine, where the rays will breakdown the DNA and RNA of the microorganism, and while not “killing”, they will sterilize those microorganisms, thus preventing them from being able to reproduce and grow.An Excellent example of the this would be the Clarifier Air Defense System air purifiers. A word of caution; all ultra violet machines are not equal and their quality and effectiveness varies enormously. The most important factor determining the effectiveness of ultra violet light is whether the rays are strong enough in the first place, which is referred to as its dosage. Also, the rays need to expose the microorganism to the light for a long enough time in order for the DNA and the RNA to be altered. Even if the ultra violet light is not completely effective, having one is better than nothing, because some of the micro organisms will be sterilized by the rays when they collide with the light or “bump around” with a side to side movement, so as not to move through the UV chamber too fast. [Note: There a Hepa filter products exists that features advanced filtration capabilities that can trap the smallest of particulate matter. These are IQAir air purifiers]
If you need an air purifier primarily for odor and/or gas control, you most likely want to look for an air purifier that will remove the majority of the particulates first by using a pre-filter, then have the gases and odors removed in the gas filter section. Gas molecules are quite small and usually cannot be removed by even the finest Hepa filter. These molecules are 0.001 microns and smaller. Therefore, they need to be removed physically by a substance or media that will trap these particles in what we call micro-pores. A good commonly used substance is: Activated Carbon. This Activated Carbon is treated by super heating and steaming which results in millions of tiny pores. Each one of these pores will be able to adsorb the gas molecules. Once these micro-pores are unable to absorb any more of the gas molecules, they are said to be saturated. This means they will not be able to adsorb gases and odors with any degree of efficiency any longer . Another method of gas and/or odor removal is through the process of chemical absorption. This is when a gas molecule is exposed to a chemical agent in combination with water molecule causing a chemical reaction to occur whereby the resulting gas molecule is broken down into a harmless by-product such as carbon dioxide and/or water. Commonly substances such as alumina silicate, alumina oxide, and potassium permanganate are used in this process. These are particularly effective at removing the gases of lighter molecular weight such as formaldehyde.
Regarding the Size and Quality of the Hepa filters in current day Air Purifiers.
The more square feet of Hepa filter media there is in an air purifier, the more particulate matter will be removed from the air before it becomes clogged. Also the air purifier will be able to remove more particulates with each pass. The quality of the Hepa filter is very important both in the material used and the design. The pleats of a Hepa filter need to be uniform so each one has the same efficiency of filtration. If the pleats are too close together they can restrict the air movement thus resulting in a loss of airflow. Some Hepa filters out there use synthetic materials rather than the traditional paper. Thin paper is usually the best material because it’s both effective at removing the highest percentage of the microscopic particulates yet it does not adversely restrict the airflow. The better quality grades of Hepa filters are extremely delicate and are easily damaged. This is why the air purifier companies that are of better quality will house the filter in such a way as to protect the actual Hepa filter material.
Particlate Matter that causes Lung Damage:
Particulate matter that causes Lung damage is of most concern because these particulates are small enough to get through sinus cavities and into respiratory systems while at the same time they are large to the point of not being able to be exhaled. It is most important when considering the purchase of an air cleaner to make sure that the product will be able to filter all of the dangerous offending particulate matter from the treated air. The size of these particulates range will from 9 microns to 0.3 of a micron in size. This is why Hepa filtration products have become such an important aspect of the air cleaning industry.
Particulates which cause lung damage fall into the same size range as do some bacteria, most molds, fumes, smoke, smog, diesel exhaust, cat allergens, pollen fragments, house dust mite allergens, settling dust, and suspended atmospheric dust. All of these particulates can cause an allergic reaction. Bear in mind that it is still necessary to filter out particulate matter which is smaller than this, however, particulates smaller than 0.3 microns have a better chance of being exhaled from within your respiratory system. Some damage causing particulate matter will still remain in your lungs. The American Lung Association believes that particulates that have been treated with a high level of ionization have a higher likelihood of sticking to certain parts of your respiratory system if inhaled so their likelihood of being exhausted from the respiratory system is low. The air cleaner’s ability to filter out particulates in the 0.01 to 0.3 of a micron range in size is considered important since this would also include certain bacteria, viruses, pet dander, house dust mite allergens, as well as smoke and smog.
Are Ultra-Violet Light Air Purifier Systems Effective?
Ultraviolet [UV] light has been a proven method known to the medical community as a highly effective way to sterilize air. By killing germs, bacteria, mold, viruses, and other microorganisms, UV has been shown to be a reliable method of sterilization. However, these results are usually achieved in a controlled environment. For example, if a surface containing germs is directly exposed to UV light of sufficient intensity (dosage) and of the proper frequency for a predetermined period of time (exposure), the surface will be sterilized. The difficultly is attaining the required level of control needed to sterilize microorganisms in an air purifier. The biggest difficulty with regard to exposure to UV light in an air purifier is when the micro organisms are moving through the air purifier at a fairly high rate of speed because of a fan. The question is: are the contaminants exposed to the rays of the UV light long enough to alter the DNA and the RNA of the micro organisms which is necessary to sterilize the air? The lower the fan speed the higher the efficiency of sterilization of micro organisms. Some products feature a hybrid approach, that is they have a UV light that bathes the Hepa filter with continuous light which in theory will kill the micro organisms that have been trapped by the Hepa filter. This means that the Hepa filter becomes part of the sterilization media and the customer no longer needs to worry about bacterial, viral contamination sitting and growing on the Hepa filter for long periods of time. There is also concern, however, as to what the UV light rays will do, over time, to the material of the Hepa filter. The Hepa material can become brittle and break up over time after long exposure to UV light causing Hepa filter life to become shortened. Air purifiers reviews and comparisons are best found on ChristineFriar.com.
Carbon and Other Types of Media for Specialized Gas Control in Air Purifiers.
There are numerous types of carbon available for use in gas filter technology ranging from coal based media to coconut shells. The main purpose of carbon filters is to physically adsorb the gas molecules into their pores. Activated carbon filters are considered best at removing VOCs (Volatile Organic Compounds) and SVOC’s (Semi-Volatile Organinc Compounds). These contaminants are of a higher molecular weight. However, carbon filters will not be very effective in humid conditions where the air contains a large amount of water molecules. Carbon is also not effective in removing the lower molecular weight gases from the air such as formaldehyde and sulfur and nitrogen dioxide. These require specialized gas control ingredients made up of chemical absorbers which chemically remove these gases from the air passing over the respective filter. What chemical absorbers do is react with a water molecules in the air as well as the gas molecules to chemically break the contaminant down into a harmless form such as carbon dioxide. Common chemical absorbers are alumina oxide, alumina silicate, and potassium permanganate. The amount of gas filter media utilized is important in measuring the effectiveness of a gas filter but is not everything. Having more micro-pores of carbon will give the filter more gas and odor removal capability. Having more micro-pores means that the gas filter will perform longer before its pores are saturated and need to be changed.
The particulate filters included with the gas filter are just as important in the air purifier. If there is an inefficient pre-filter in front of the gas filter then a great deal of the micro pores in the carbon will be used to collect the particulates not removed by the pre-filter. Therefore, a gas filter containing many pounds of activated carbon could prematurely become saturated. The design of the gas filter is also important with respect to airflow. A gas filter containing fine activated carbon will cause a lot of resistance to airflow, however, if the gas filter consists of larger pellets, the air will flow through the filter much easier. Also, a pleated design can result in a larger surface area of carbon thereby increasing the efficiency in the rate of gas removed since gas molecules have a better chance of being adsorbed with a larger surface area.
Other Air Purifier Technologies Worth Consideration.
An example of mechanical filtration are Hepa filters. The advantage to this filtration method is that there is no reduction in its efficiency at removing particulate matter from the air over time. Actually a Hepa filter will become more efficient as it collects more particulates, because it is so fine. The only reason you need to eventually change it is because it will start to effect the airflow through the air purifier, which will result in a loss of air cleaning capability and also there is the possiblity of damage to the motor due to heat buildup. Another disadvantage to this type of filtration is that they tend to be noisy, especially when the air purifier is operated on the higher speeds. Their filters are replaceable and can be rather expensive, especially on the more efficient high quality air purifiers which remove more from the air over a shorter period of time.
Another type of air purifier technology is the electronic air purifier. They frequently utilize a combination of technologies to clean the room air. An electronic air purifier works by creating an ionic charge which attaches to the particulate matter. These are frequently termed an ‘Ionizer’. In theory, by creating an electrical charge with the outcome being that the particulate matter becomes negatively charged, one can cause the particulates to precipitate out of the indoor air onto the floor to be vacuumed or the particulates will stick to a plate inside the ionizer.
There are four different forms of electronic air cleaning:
1. The first is called an electrostatic precipitator, which consists of a series of metal collection plates that are oppositely charged to the ionized particles. The particles will be attracted to these metal plates similar to a magnet with the result being to collect particles as small as 0.1 of a micron. The drawback to this type of air purifier is as the collection plates collect the particles and their surface areas become covered by the particulates, their ability to attract more particlulate will continue to decrease until the plates are taken out and cleaned. In the best products available today one may start out at an efficiency of 80% and degrade down to as little as 20%. Thus, it is absolutely imperative you clean the metal collection plates on a regular basis as frequently as weekly or in some cases; daily. These types of air purifiers will generate a small amount of ozone, enough to smell and some may not like that scent. Most of these machines generate safe levels of ozone which is quite good at eliminating foul odors.
One of the best examples of this technology is the Friedrich C90 air cleaner, a unit rated number one by a respected consumer testing magazine.
2. Another type of electronic air purifier uses a media charged filter. These products utilize oppositely charged particles inside the electrostatic filter to collect the ionized particles in the air. They are able to collect these particles, some as small 0.1 microns in this filter. Like Hepa filters the electronic filter will start out at a high efficiency, as much as 80 to 90 percent, decreasing as the surface area of the filter becomes clogged with particulate matter. The biggest decrease will be suffered in the smaller particle range. Because this is not a Hepa filter, it is not able to mechanically remove the microscopic particulates due to the fact that it’s filter is not as fine nor as thick as the Hepa filter. It will, however, maintain its ability to filter out the larger particulates better than the electrostatic precipitator because it’s filter media is small enough to collect the larger particles without having to rely on the opposite charging attraction needed for the smaller particulates. Once the older filter needs replacing, you can have a decrease in the efficiency to as low as 50% if it is not replaced with a new filter.
3. The third type of electronic air purifier is the negative ionizer. This machine attempts to clean the room by basically eliminating the particulates from the air. The particles are not removed from the room just from the air. The way it works is the particles are drawn into the machine where they are ionized and negatively charged. From there they are sent back into the room where they are attracted to the positively charged walls, furniture, positive and neutrally charged particulates where they collide with them until they are heavy enough to fall to the floor. The result is that the air becomes free of particulates and the particle count is reduced. The drawback to this type of air purifier is that all of your particles land up on the floor, walls, and furniture. As the particles lose their charge they will release themselves from the walls falling back into the air. Also, unless you are regularly vacuuming and dusting, the particles will be kicked back into the air when any air movement occurs by a door being opened or someone walking in the room. A major concern is that if an ionized particle is inhaled, it is more likely to stick to the walls of your respiratory system thus increasing the chance of an allergic reaction. The advantage of these kinds of air purifiers is that they will be quiet because there is no resistance to air flow and there are no filters. Also there is a tendency to use them for treating a large amounts of air, because if a smaller, quieter fan is used, it will still result in a large amount of air being circulated through the machine. There are no expensive filters to replace such as with Hepa filters and no pre-filters that need to be cleaned. Still, we tend not to recommend negative ionizers except if they are used in conjunction with other air cleaner technology.
4. The fourth and more controversial air purifier is an ozone machine. Its whole premise is based on the use of ozone to clean the air. The manufacturers of ozone generating machines claim that the air is cleaned by oxidizing gases, chemicals, and odors thereby removing them from the air. Since there are no filters to trap the particle matter, nor an ionizer to precipitate or capture the particulates, we wonder just how effective ozone generators are as air purifiers. You may be familiar with their use in the hotels where they are sometimes used to prepare rooms for their customers. The machine is put in place and turned on high while windows and doors are closed and the room is unoccupied. While the machine is in operation it will remove the smell of smoke and odors and leave the room smelling fresh. Once the room cleaning is completed, the hotel staff will turn off the machine, and open the windows to air the room out and to rid the room of the smell of the ozone.
There are also air purifiers that use a combination of a pre-filter to collect the large particulates, and a UV light. These air purifiers will emit ozone into the room, which reacts with the gases and odors in the room and chemically breaks them down.
The main advantage of electrostatic precipitators are there are no expensive filters to replace and they are quieter than Hepa filters. The disadvantages are the steady reduction in efficiency as the metal plates become dirty if regular cleaning is not conducted.
The main advantage of media charged filter electronic air purifiers are that they are quiet and clean a large amount of air. The disadvantages are the cost of the replacement filters and the gradual drop in efficiency as the filter becomes dirty.
The main advantage to negative ionizers are that there are no filters to clean or change and they are quiet. The disadvantage is that the particles are not actually removed from the room, and can work themselves back up into the indoor atmostphere re-polluting the room. Usually caused by movement such as doors opening and closing or by people moving around inside the home.
The advantage of the fourth type of electronic air purifier, the ozone machine, is the ability to eliminate bad odors. For smoke odor removal after smoking or a house or room fire they are the air purifier of choice because of the effectiveness and low cost. The disadvantage is the possible discomfort to some caused by excessive ozone.