What You Need to Know about HEPA and Active Carbon Filters

If you’re shopping for any air filtration product — whether it’s a mask, A/C filter, or a filter for your vacuum — you’ve probably run across acronyms and words that you’ve seen before or have no idea what they mean.

HEPA. Microns. Active carbon. These usually aren’t everyday topics of conversation. But they’re important when you’re trying to find the best air filter for your needs.

A close up of a HEPA filter

What does HEPA mean?

This is one of the most common acronyms in the air purification market. Consumers and businesses rely on the HEPA certification when choosing what products to buy for their homes or offices.

HEPA stands for High Efficiency Particulate Air. That’s a mouthful to say that HEPA filters trap small, harmful particles in the air and keep you from breathing them in. To be HEPA-certified, a filter must remove AT LEAST 99.97% of dust, pollen, mold, pet dander, smoke, and dust mites.

HEPA filters are made with a fine mesh of glass fibers that create sort of a maze for air. The particles we don’t want to breathe – like dust, pollen, and dander – get trapped in the maze and stuck to the fibers, while clean air can escape. The result is a room of dust-free, allergen-free, and overall clean air for us to breathe.

True HEPA filters (such as the ones made by RZ) trap 99.97 percent of particles that are 0.3 microns in diameter. That’s less than one-millionth of a meter! To put it in perspective, it’s several hundred times smaller than an average human hair (100 microns) and smaller than the average dust particles in the air:

  • Spores: 3 – 40 microns
  • Mold: 3 – 12 microns
  • Bacteria: 0.3 – 60 microns
  • Car emissions: 1 – 150 microns
  • Pure oxygen: 0.0005 microns

The RZ AIRflow uses a center HEPA filter to trap airborne particles and purify the air coming from PTAC units. On average, the RZ AIRflow provides maximum room purification within 45 minutes for rooms up to 315 square feet

What about Active Carbon?

A close up of an Active Carbon filter

Like HEPA filters, active carbon filters are crucial to removing odors and particles we don’t want in our bodies. You likely already use active carbon and may not know it. It’s used to clean municipal water, manufacture soap and toothpaste, and even remove caffeine from decaf coffee.

Active carbon filters are pieces of black mesh with little bits of charcoal scattered throughout. This creates a high surface area of carbon that allows it to attract and trap particles. One small gram of activate carbon has a total surface area of more than 32,000 square feet. That’s nearly 350 acres of surface (or more than 1/3 of Central Park) in a pound of activated charcoal.

This surface area is important because of how carbon removes impurities from whatever flows around it. Activated carbon removes pollutants in air through a process called adsorption, not to be confused with absorption.

In absorption, with a “b,” particles are drawn into something. Think of a sponge soaking up water. In adsorption, with a “d,” particles stick to something, similar to a magnet and metal shavings. That’s why surface area is important: the more surface area a piece of carbon has, the more particles can stick to it.

Think of something that smells bad, like a wet dog. When Fido gets wet, the bacteria and other organisms living in his fur release smelly chemicals that enter the air as the water evaporates. The chemical molecules are attracted to the active carbon. So when the air enters the filter, the odors stick to the carbon, and you’re left with clean and better-smelling air.  

An RZ AIRflow connected to a PTAC unit

Why both?

The RZ Airflow uses both HEPA filters and active carbon filters to purify your air because both do things that the other can’t. HEPA filters are better at removing physical particles like dust, pollen, mold, and other allergens. Carbon filters are better at eliminating odors, smoke, and other gaseous particles.

Working together, these filters give you clean, breathable air and top-quality purification.