What’s the Difference Between Air Purification, Filtration, and Ventilation?

By Dan Dearden, CAFS

If you’ve ever shopped for air-cleaning products, you’ve probably seen the words purification, filtration, and ventilation used interchangeably. Unfortunately, that’s often misleading—and it drives me crazy. These terms describe very different processes, and knowing the difference can save you money and help you make smarter choices for your home’s air quality.

Let’s break it down.

1. Air Purification

Air purification means removing impurities from the air—so that what’s left is pure, clean air made up mostly of nitrogen, oxygen, and a few inert gases.

But here’s the problem: many devices marketed as “air purifiers” don’t actually remove anything from the air. They just change it.

Photocatalytic Oxidizers (PCOs)

PCO devices are often advertised with eye-catching claims like “99.99% reduction of contaminants.” What they don’t tell you is that these results come from very small sealed lab chambers, not real homes.

In reality, PCOs add chemicals to the air, such as hydroxyl radicals and super-oxygen ions. The only proven effect they have is to slightly increase the death rate of bacteria, viruses, and other pathogens—by about 10%—in a sealed lab setting. No study has ever shown measurable improvement in an actual home.

One manufacturer even tested a whole-home PCO unit in a sealed lab chamber just 21” x 21” x 21”—about the size of a small cooler. That’s over 53,000 times smaller than an average home! It’s about as scientific as using a stick of dynamite to kill a mosquito.

Ionizers

Ionizers make similar claims, boasting about “96–99% reduction of contaminants.” While they can help particles clump together (a process called agglomeration), those clumps just fall out of the air—onto your tables, counters, furniture, and floors.

When ionizers first appeared in the 1980s, homeowners quickly noticed the black ring of grime forming around the device. Sure, the air was cleaner—but the pollution was still in the room, just relocated.

Ions have been proven to slightly increase the death rate of bacteria, viruses, and other pathogens—by about 10%—in small sealed laboratories. However, just like PCOs, no study has ever shown measurable improvement in an actual home.

Bottom line: If a “purifier” doesn’t physically remove contaminants from the air, it’s not truly an air purifier.

2. Air Filtration

Air filtration is the process of purifying air using an air filter. It’s the most reliable and proven method of improving indoor air quality in labs and homes.

Since 1986, air filters have been rated by the ASHRAE 52.2 standard, which assigns a MERV (Minimum Efficiency Reporting Value) rating from 1 to 16:

• MERV 1–4: Basic protection (large dust, lint)

• MERV 8–11: Fine particles (pollen, pet dander, mold spores)

• MERV 13–16: Very fine and ultrafine particles (smoke, bacteria)

Watch Out for Misleading Claims

Some manufacturers still advertise outdated or meaningless efficiency numbers. For example:

• A company might claim “97% arrestance,” but that test was replaced by the MERV standard decades ago. In reality, that filter might be only MERV 6, which captures just 35% of large particles and none of the smallest ones.

• Another company advertises “97% efficient at 0.3 microns” for a “polarized media” filter. But in real-world testing, it performed like a MERV 10—catching no nanoparticles on the first pass. Their fine print admits that particles are captured “on subsequent passes,” which only happens in a sealed test chamber by continuously recirculating the air through the filter over and over and over again. This is an invalid test procedure that does not correlate with a home environment.

The truth: Only filters with verified MERV ratings have been tested and proven to remove contaminants effectively.

3. Ventilation

Ventilation means bringing in clean outdoor air to dilute indoor pollutants.

Some contaminants, like formaldehyde, mix with air at a molecular level and can’t be easily filtered out. The best approach is twofold:

1. Remove the source of the pollutant (for example, certain pressed-wood products or harsh cleaners).

2. Dilute what remains by introducing fresh air from outside.

The most energy-efficient way to ventilate is with an Energy Recovery Ventilator (ERV).An ERV replaces polluted indoor air with fresh outdoor air while transferring heat and humidity between the two airstreams—so you keep your comfort and efficiency. This process keeps your air fresh without wasting the energy you’ve spent heating or cooling your home.

Quick Summary

Term	What It Means	How It Works
Purification	Removing impurities from the air	Should remove contaminants—not just kill or displace them
Filtration	Purifying air using a physical filter	Uses MERV-rated filters to trap particles of all sizes
Ventilation	Diluting indoor pollutants with outdoor air	Adds clean air and exhausts polluted air, often through an ERV

Final Thoughts

If your goal is truly clean, healthy indoor air, focus on verified filtration and controlled ventilation—not marketing buzzwords.

At Essential Air Products, we believe that air quality should be measured by real science, not exaggerated claims. Every NovusAer system we build is backed by proven data and decades of hands-on experience.

Because when it comes to your home’s air, clean should really mean clean.