The creation of the atomic bomb was at least good for something.

In the 1940s, when the super-secret push to build the world’s first atom bomb began in earnest, Manhattan Project engineers needed a way to capture radioactive particles suspended in the air during experiments. They devised a filter composed of a series of arranged fibers, with the aim of trapping particulate in the air through a vacuum or ventilation system.  And so, the High Efficiency Particulate Arrestance Filter—or HEPA filter—was born. And it’s what makes a commercial grade air purifier truly tick.

So what makes a HEPA filter so special?

It’s all in the mat and the weave of fibers in the filter itself. HEPA filters use hundreds of thousands of fiberglass fibers—incredibly small and sticky for particles that try to pass through them.

This tight weave of fibers then captures particles larger than 0.3 microns in size. For a frame of reference, a human hair is anywhere from 50 to 100 microns in diameter, so we’re taking about unbelievably small particles being trapped in the fiberglass fibers. The weave of a HEPA filter then allows air to pass through, with germs, volatile organic compounds and allergens like dust and pollen, trapped inside.

HEPA filters capture all that crud three different ways: through Interception, Impaction and Diffusion. With Interception, the path of particles is interrupted by the weave of the filter and the fibers intercept the particles, making them stick to the fiber.

With Impaction, the particles crash into the fibers, sticking to them. And with Diffusion, small particles slam into each other, causing them to veer off course in airflow and stick to the fibers of the HEPA filter. That’s why HEPA filters have a waffle-like appearance—the irregular shapes cause all sorts of havoc with airborne tiny particles, making them collide.

One thing to note, however: there are HEPA pretenders out there. In order to be a real HEPA filter though, a filter needs to be able to capture the particles larger than 0.3 microns in size. Then, the HEPA filter captures 99.97 percent of all airborne contaminants. Like the complete line of AeraMax Professional commercial grade air purifiers.