Dec
A common question that people ask when purchasing air purifiers from AirFanta is its filter grade – why are H11 filters used instead of H13 filters?
The short answer is, despite lower filtration efficacy, H11 filters are more effective at cleaning the air than H13 filters with its superior Clean Air Delivery Rate (CADR).
Let’s find out why.
What are the different types of filters?
There are many types of filter grades for air purifiers and HVAC systems, such as:
MERV-13: 75% filtration efficiency
H11: 95% filtration efficiency
H12: 99.5% filtration efficiency
H13: 99.95% filtration efficiency
U17: 99.999995% filtration efficiency
The filtration efficacy for a filter tells us the percentage of 0.3 micron size particles captured by the filter when they pass through it. However, it’s just one part of the equation.
The trade-off with higher efficiency filters
Filters that have higher filtration efficiency have higher pressure drop (resistance). This means that the volume of air that passes through a H13 filter in a single pass is less than that of a H11 filter. In order for a H13 filter to achieve the same air cleaning performance or CADR as a H11 filter, the fan needs to operate at a higher speed, resulting in higher electricity consumption, noise level, and heat generated.
Hence, even though a H11 filter filters 4.95% less particles than a H13 filter, it provides better air cleaning performance as more air can pass through the filter in a single pass, allowing the air in the room to be cleaned at a faster rate.
What about filters with lower efficiency?
While a MERV-13 filter has lower pressure drop than a H11 filter, it only filters 75% of particles that pass through it, resulting in lower air cleaning performance or CADR than a H11 filter.
How do we know this?
We know this because AirFanta tested filters of various standards, such as MERV-13, H11, and H12, to find out which type of filter would deliver the best CADR
According to internal test results provided by AirFanta, MERV-13 and H12 filters produced a CADR that is 10 to 20% less than a H11 filter.
Here’s the data. Take note that this is assuming the type of fan and its power consumption are the same:
- MERV-13 (75% filtration efficiency, 7.2 Pa): 968.44 m³/h x 75% = 726.33 m³/h
- H11 (95% filtration efficiency, 12 Pa): 883.49 m³/h x 95% = 839.32 m³/h
- H12 (99.5% filtration efficiency, 16.8 Pa): 713.58 m³/h x 99.5% = 710.01 m³/h
As we can see from the calculations above, a MERV-13 filter has the lowest resistance, allowing the most air to pass through the filter in a single pass. However, it captures far less particles than the other two, resulting in a CADR that is slightly higher than H12, and far lower than H11.
Whereas for H12, the biggest problem is its high resistance, resulting in less air passing through the filter in a single pass. That is why even though it has slightly higher filtration efficiency than a H11 filter, its CADR ends up performing worse than both H11 and MERV-13.
We also have to keep in mind that going with either MERV-13 and H12 would have resulted in noisier fans and higher power consumption if AirFanta wanted to use either of them to match the same CADR as H11.
If two different types of filters deliver the same CADR, does the one with higher filtration efficiency perform better?
No. If the CADR is the same, the air cleaning performance is the same, regardless of filtration efficiency.
However, other factors, such as power consumption and noise levels, will be higher with the filter that has higher efficiency. That is because the pressure drop for the filter with higher efficiency will require the fan to work faster to process the same volume of air as the filter with lower filtration efficiency.
Imagine you have two different cars, Car A and Car B – both have the same top speed, but Car A is half the price of Car B, and Car B is larger than Car A. While both cars may have different specifications such as size, engine, and tires, they have the same performance as both cars have the same top speed. Both cars will get you to your destination in the same amount of the time.
Scenarios in which higher filtration efficiency is useful
While filtration efficiency isn’t important for most premises, scenarios, and settings, there are a few niche scenarios where it would come in handy.
Biosafety cabinets (BSC), which are designed to protect workers from exposure to biological hazards and infectious agents, will benefit from filters with higher filtration efficiency. Such filters include ULPA (Ultra Low Particulate Air) filters that have 99.999995% filtration efficiency.
ULPA filters, of course, would require much more powerful fans than fans found in room air purifiers, and they will also incur significantly higher maintenance costs. That is the reason why you do not see room air purifiers using ULPA filters even though they have a ridiculously high filtration efficiency, as their pressure drop will significantly reduce a room air purifier’s CADR and they are not practical for most settings outside of a BSL laboratory.
Conclusion
Based on these test results, it was determined that H11 filters are the best option with its superior CADR, as well as its good balance with air flow, energy consumption, and noise levels.
Looking for an air purifier with superior performance, affordable price, good noise levels, and low power consumption? Check out the AirFanta 3Pro:
Room Air Purifier
