So, we have put together this guide to show you what to look for and to help you make a fair comparison.
As allergy and asthma sufferers ourselves, we believe what you should care about is having the cleanest air in your room or home so you don't breathe in harmful pollutants. Whether pollutants are “destroyed” or held in a filter, is irrelevant. The goal is to have the best indoor air quality.
Therefore, when we talk about performance, we mean how clean your air is in a living area.
But before we can answer the question of how our products compare in cleaning your air, we need to first consider what you are looking for the air purifier to remove.
AllergensMost people we talk with are looking for allergy relief from airborne particulates. This includes things like dust, pollen, mold spores, pet dander, etc.
For the removal of these airborne particles a true HEPA filter works best in providing the cleanest air. While this technology has been around for decades, we have not come across anything that can beat it for particle removal.
HEPA filters have the highest efficiency in removing airborne particles and this improves as the filter becomes dirty. For best performance the key is to have a highly efficient filter and good air flow. To learn more, see what is a HEPA filter.
In some marketing for electronic filtering technologies you are shown its ability to destroy allergens versus HEPA filters. There are two problems with this. One is that the air is moving quickly through the air purifier and to kill a virus you need much more contact time. If the air moves through in a fraction of a second why are you showing the disinfection rate based on hours of contact time? And two, to it does not show how clean the air in your room is.
Isn’t that the purpose of an air purifier?
How to Compare PerformanceThe industry standard for comparing air purifier performance in the removal of airborne particulates is called the CADR (Clean Air Delivery Rate). It utilizes a combination of the filter efficiency and air flow to show the volume of clean air produced.
The challenge for shoppers is only about half of the air purifier brands publish their CADR numbers so it is more difficult than it should be to compare.
The CADR number is something you should ask about before buying an air purifier. If the CADR is not shown in the specs, we have noticed it is often because the brand doesn’t want it known. Having good results is difficult because high efficiency filters, strong air flow and a low noise level are opposing forces.
Here are the certified CADR numbers for the EJ120 air purifier:
- Tobacco Smoke CADR: 323
- Dust CADR: 332
- Pollen CADR: 360
How to Compare when a Product Doesn’t Show the CADRSome brands will show something related such as the size of a room it will clean and maybe the associated air changes per hour.
While these are not independently tested and certified results, it’s something. Often, you will see this presented as 1 or 2 air changes per hour.
For example, you may see a 1,000 sq ft room coverage with one air change per hour.
Here’s how you can roughly equate this to a CADR.
The CADR is in CFM (cubic feet per minute). So, assuming the ceiling height is 8 ft, the 1,000 sq ft room has 8000 cubic feet (8 x 1,000). To convert to minutes divide by 60 to get to 133 cfm.
Assuming the filter removes 100% of the particles (which can be a big if), then the 133 cfm x 100% = 133 CADR.
Finally, compare this 133 CADR to the 323-360 CADR for the EJ120.
What Else to ConsiderWe believe the CADR is a starting point for comparison. It considers the efficiency and air flow through the filter however it does not show how efficient the filter is, how it will perform over time or the quality of the fan.
This is important since the most efficient filters will remove the smallest particulates and the more filter media it has the better it will do over time.
Filter QualityTo get to this, it’s good to know the quality and quantity of the HEPA filter media.
In the EJ120 the HEPA filter has been independently tested to remove 99.99% of particles at 0.3 microns. The testing was done with 3 units with these results.
The filter size is 16”x16”x2.5” with 36 square feet of HEPA filter paper. A filter with these specs can be expected to give you a high filtering ability for a year in most environments.
Fan QualityFurther, the EJ120 delivers this cleaning ability while only drawing 52 watts since we use a super-efficient German motor. It costs more to use a better motor/fan but we feel it makes for a better air cleaner.
The EJ120 fan has a high life expectancy run time of 118,738 hours (almost 13 years continuous use).
Gases/VOC’sIf you are interested in volatile organic compound (VOC) or gas removal, it’s important to know that gases are so small they require a different solution since they will pass through the HEPA filter fibers.
In the EJ120, we use coconut shell based activated carbon that has been specially treated so it can adsorb a wide range of gases, VOC’s and chemicals. See this page to see the test results
- Formaldehyde Removal: 99.78% (48 hr test)
- Sulfur Dioxide Removal: 99.39% (48 hr test)
- Nitrogen Dioxide Removal: 99.97% (48 hr test)
Electronic filtering technologies like PCO and PECO utilize more of an oxidation process as opposed to adsorbing the gases.
To date we have not seen side by side comparisons for the removal of VOC’s, chemicals, and gases to be able to comment on how the various air purifiers clean the air in a room like the allergens.
Keep reading below to see what VOC, chemical and gas test standards are coming for the future.
SmokeSmoke is made up of a host of airborne particulates and gases. So, it requires a combination of the allergen removal and gas removal that are described above.
For the EJ120, this is the carbon and HEPA filters working together to deliver a comprehensive smoke removal solution. In the customer reviews on the EJ120 product page you can search for "smoke" in the reviews to see the experience of other customers.
How to Compare VOC RemovalUnfortunately, there is not yet a CADR type industry standard for measuring and comparing VOC or gas removal. These standards are under development in the US and should be in use within the next two years.
Until then, you are at the mercy of any testing that the manufacturer provides.
We use activated carbon in our machines. This is a good natural absorber of a wide range of gases and does not produce ozone, an indoor air pollutant.
The most important attributes are quality of the carbon and the carbon surface area.
We see frequent comparisons of carbon based on the weight. While there is some validity to this, the amount of surface area matters more in gas removal performance.
If you are looking for massive amounts of carbon, you can use our ERIK650A and purchase the main carbon filter. This is a 12” deep v-bank filter with 14 pounds of carbon. In addition, the ERIK pre-filter has another 3.5 pounds of carbon.
GermsIf germs are your primary concern, then a low efficiency filter or carbon filter will not be effective.
What Size are Viruses and Bacteria?Virus particles range in size from 0.02 to 0.4 microns. Most bacterial cells range in size from 0.2 to 10 microns. Common E.coli and rod-shaped bacteria are generally 1 micron by 2 microns.
How well does the EJ HEPA filter work for 0.02 to 0.4 microns?Testing standards are set at the 0.3 micron size so testing data is not readily available for the smaller sizes. To address we sent our EJ120 HEPA filters to one of the few test labs that will test the performance against virus sized particles.
The lab report showed the performance for nano-sized particles for our filter. 99.99% of airborne particulates at 0.3 microns, 99.8% at 0.10 microns and 99.8% at 0.02 microns (20 nanometers).
There are two forces at work in a HEPA filter. Interception is the effect of the fibers catching particles that are larger than the opening in the filter fibers. Diffusion is the effect of the smallest sized particles that collide with one another and therefore are able to be collected in the HEPA filter fibers. The efficiency related to diffusion increases significantly as the particle size approaches zero.
According to Science Direct, “High Efficiency Particulate Air (HEPA) filters are available that have efficiency greater than or equal to 99.97% even at the MPPS (most penetrating particle size). For particles with diameters between 20 nm (0.02 microns) and the MPPS, HEPA filter users should be confident that the efficiency will be at least 99.97% when the filter is new.”
In short, for nano-sized particle removal the higher the HEPA filter efficiency, the better.
Electronic filtering such as a UV-C lamp, PCO or PECO show some positive results although as mentioned above, this is based on contact time that is significantly longer than the time it takes the air to pass through an air purifier. From what we have seen, any disinfection takes place on what is held in the filter. Since viruses will die naturally on a surface, to us it seems irrelevant whether you kill it on the filter or let it naturally die.
SummaryIn this article we have provided tips on how to compare air purifiers in their ability to provide clean air in a room.
To find the best product it’s important to understand what you want removed from the air and then select the product with the best performance to address that issue.
In our experience, HEPA filtration is the best technology to provide the cleanest air for the removal of airborne particulates. High quality carbon can also be effective for the removal of a wide spectrum of gases, chemicals and VOC’s.