There is a battle among pleated HVAC filter manufacturers - MERV-8, MERV-9, and MERV-10 Which is "best" for your facility and how different are these prodcuts really, seeing as not too long ago they were all MERV-6 or 7? Frustratingly with ASHRAE 52.2 and the MERV system you would think that a filter with a value of "10" is significanty better than "8" and although there is more particle capture there it isn't as much as you would think given the big jump in numerical value.
Why ASHRAE 52.2 doesn't tell the whole truth: One of the most deciteful things I think anyone can do is tell a partial truth, becasue while the "fact" may be accurate without the proper context (the whole truth) it can be misleading. Although it is true that 10 is a larger number than 8, and MERV-10 does capture more particles than MERV-8 captures the question that remains is HOW MUCH more does it capture.
Looking at ASHRAE 52.2 on it's face, there are 16 values so it would be logical to think that each time you increase you are getting a proportional amount more air cleaning. The problem with this logical conclusion is that 52.2 tests the particle removal efficiency of an air filter with no basis of what the filter will encounter while it sits in your HVAC system. It only knows that "X" filter removes "Y" size particles at a rate of "Z%" it does nothing to tell you how that correlates to the cleanlienss of air in your building. Sure, the 10 will take out 50-65% of particles 1µ-3µ while an 8 only takes out 20%+ of that same particle size range - but what is the impact of that on the air quality of your facility???
How Much More Does 10 Really Capture: With 99% of all particles in the air being sub-micron in size the answer is - Not much (both MERV 8 and 10 are not even mesaured at that particle size) In reality it is a statistically insignificant amount that is dependant on many variables, in some in-situ testing we've found 10 to take fewer particles out of the air. The above chart shows the distribution of particles in the air by count, and then highlights the removal rate of both 8 and 10. You may need to hit the magnify button on your device to see the removal portion.
Filter salespeople want to be different (all us salespeople are taught early on that differentiaion is a key to sales success) so when one has a pleat with a different value than the other and that can be spun as a benefit they are naturally, almost instinctively, inclined to do so. As a rep for over a dozen different lines with both products available to our customers we take a different road - EDUCATION. We would rather show you what the difference means for your facility and the occupants within it instead of trying to "upsell" anyone, and the occupants of your building and your HVAC equipment will not notice a difference in IAQ between these two values.
Also, we took a 52.2 report at random from one of our products that test as a 10 and one that's an 8 and put them on the same fractional efficiency chart so you could see those curves side-by-side instead of a side-by-side coming form the same company. What we've found is the MERV-10 manufacturers tend to use curves for MERV-8 that are on the lower bound of the standard instead of what is commonly found in the marketplace. By comparing the data from two different manufacturers we are able to give you a clearer picture here:
Is MERV-10 worth more? Probably not. If you can get it for the same price is it a decision maker? Probably not - build quality and dust holding/longevity of the filter is likely more impactful than simply being 10 instead of 8. If all other factors are truely equal, then is it worth it? Of course. Will there ever be a filter test standard that is straight-forward and honest with facility managers and other "non filter" people? Yes, it already exists and is called ISO 16890, the rest of the world uses it and it is currently under review by ASHRAE for adoption as a US standard as well. If you'd like to learn more about ISO 16890 click here.