With any air purifier, performance is crucial.

But there are myriads of air purifiers on the market, and long-term performance can vary drastically. Some last two to three weeks before losing efficiency. Some are good for a couple of months before losing half their efficiency. Others last for five months or more – and in IQAir’s case, as long as 2 to 4 years without ever losing efficiency.

Why the huge difference? The devil’s in the details – or in this case, the efficiency testing methods and results.

So before you go to the store and fall into the sea of acronyms (like the infamous CADR rating) and shaky efficiency claims, read on for our bite-size crash course on the motherlode of all air purification ratings: cumulate clean mass, or CCM.

Forget CADR: it’s all about CCM

In the GB/T18801-2015 national standards, implemented in China during March of 2016, four key indicators are noted for measuring an air purifier’s long-term performance:¹

• Clean Air Delivery Rate (CADR)
• Cumulate clean mass (CCM)
• Cleaning energy efficiency
• Noise

You may hear a litany of CADR rating claims when you shop around for air purifiers, but CADR rating is basically just a speed test: all it measures is how quickly a purifier cleans the air, not even really how clean the air is that comes out. Even an air purifier CADR above 350 is essentially meaningless without some context.

When it comes to long-term performance, CCM is the most relevant metric.

You don’t need to get into the weeds to know why, but just in case you’re curious, CCM is tested for particle pollution as follows (per the GB/T18801-2015 standard):

1. Measure the CADR of the purifier in normal settings to get an initial value.
2. Light up a cigarette in a three square-meter chamber and blow the smoke around briefly with a fan.
3. Turn off the fan and measure particle pollution in the chamber.
4. Put the air purifier in the chamber and turn it on to the setting you want to test.
5. Turn on the fan that’s in the room, too, and seal off the chamber.
6. Light 50(!) cigarettes one after another (not at the same time!) in the chamber and wait for the purifier to get the particulate concentration below 0.035 milligrams per cubic meter (mg/m3).
7. Turn off the purifier and let it sit in the chamber for another 30 minutes before taking it out.
8. Repeat these steps for 100 cigarettes, 150, 200, and beyond until the CADR is less than half of that initial value you got in step 1.

Sounds kind of fun, huh? And then you get to do it again for other gases, such as formaldehyde, following similar steps for filtration media for gases, such as activated carbon filters.

The final CCM measurement you get indicates the continuing air-cleaning power of a purifier. It’s assessed by measuring the sheer volume of particulate matter and formaldehyde that can be efficiently filtered by the purifier before it starts to lose its overall efficiency over time.

The results are categorized as follows:

What’s the takeaway here? The higher the P and F value, the greater your purifier’s long-term performance. And it doesn’t get any better than P4 and F4.

Just how important is CCM?

In a nutshell, the higher the CCM is, the better the overall long-term performance and stability of the product.

And CCM is a good indicator of how much your purifier will protect you from dangerous indoor air pollutants. The Household Indoor Eco-Environment Health Report released by Tsinghua University shows that the most hazardous indoor pollutants are:

• Formaldehyde
• PM2.5
• Benzene

Let’s focus on formaldehyde, an IARC Group 1 carcinogen. It’s widely emitted from adhesives, plates, wall coverings, polyester carpets, paints, and coating.² If it’s not properly disposed of, formaldehyde takes three to 15 years to release fully. As a result, the volume of formaldehyde may still be higher than normal even if you ventilate a newly renovated place with the windows open for six months or even as long as two years.

During those years while pollutants like formaldehyde stay volatile, you may really need just to close your windows and turn on your air purifier, especially when outdoor air quality is worse than that indoors. In cities like Beijing, where indoor gases released during renovation season combines with pollen and the particulate matter and gases associated with heavy smog, the role of an air purifier becomes even more crucial – and the CCM rating will tell you much of the story about how much of that pollution will be effectively absorbed in the long term.

How big a difference can an air purifier make?

The bottom line is this: CCM is shorthand for excellent long-term performance. And we at IQAir are all over it.

But don’t take our word for it.

In the List of Outstanding Air Purifiers Regarding Particulate CCM issued by China Household Electrical Appliances Association, IQAir’s HealthPro^® Series room air purifiers ranked among the best as well as being named the only product whose particulate CCM rating is tested above 1 million mg, 8,233 percent higher than the P4 level.

And try the GCX™ Series air purifiers for even more extreme protection. These robust purifiers filter not only particulate matter but also harmful indoor chemicals, odors, and gases like formaldehyde in indoor spaces of any size with up to 32 pounds of sorptive material. It’s one of the most powerful purifiers in relation to CCM: it reaches over 2.27 million mg (22,000 percent higher than the standard P4 level!), and 27,000 mg for formaldehyde alone (1700 percent more than the F4 level dictated in the New National Standards).

These incredible CCM numbers explain why HealthPro and GCX Series purifiers are consistently rated as the best purifiers for long-term purification performance: they filter out almost particulate matter and formaldehyde from your indoor air even after years of use. The efficiency of many purifiers drops by as much as 75 percent in the first few months of use, but using CCM and EN 1822 as a benchmark, IQAir systems are tested and certified to retain their efficiency for years after you first buy them.

Now you know what to look for in an air purifier and why many air purifiers don’t last long against even normal levels of indoor pollution.

Keep an eye on CCM when you buy an air purifier. This way, you know just how powerful your purifier will be at removing particles and gases and how much your air purifier will truly help clean your home in the long run.