Why is it Important to Change Your Vacuum Filters?

Whether it’s your household furnace or central air, your vacuum cleaner, or your humidifier or air purifier, taking care of your filters is important. This is especially true if you suffer from allergies or any other sort of breathing malady. To understand why it’s so important to change your filters, you need to understand how filters work. It’s also important to understand how filters are rated; after all, not all filters are created equally.

In general, filters in your vacuum cleaner and other household fall into the realm of mechanical filters. This means that the filter physically traps particles in the filter materials. This trapping makes them very good at removing larger allergens from the air. This includes things like animal dander, dust, mold, and pollen. As long as the air is blowing them around, mechanical filters can remove them from the air. Better filters remove smaller particles from the air, with the best filters able to remove particles that are as small as 0.3 picometers in diameter.

HEPA What?

Most of us know about HEPA filters, whether from ads or from the little sticker on your vacuum cleaner. HEPA is an acronym for High Efficiency Particulate Arrestance. The HEPA standard is regulated by the United States Department of Energy. To qualify for a HEPA rating, the filter has to remove 99.7% or more of particles that are 0.3 microns in diameter. This is because 0.3 microns is where a HEPA filter is most inefficient, so if it’s least efficient there, it will be much better at trapping larger and some smaller particles.

A HEPA filter relies on three mechanisms to trap particles to filter fibers: interception, impaction, and diffusion. Interception is the mechanism of direct contact between the filter and the particle. This is where the filter does act like a sieve or colander. Impaction relies on the weave and thickness of the filter. Air is forced to follow a meandering path through the filter because of this weave. As the particles flow through the filter, they impact the fibers and are trapped. The last mechanism is diffusion. Diffusion is a more technical way for particles to be trapped. Particles that are smaller than 0.1 microns are slowed and delayed by impact with gas molecules. This slows these tiny particles until they can be trapped by interception or impaction.

To put it simply, a HEPA filter doesn’t just remove pollutants by acting like a single sieve and trapping particles in a tight mesh. That’s part of it, but the overall weave of the filter is made up of multiple layers with each layer oriented in a different direction. Think of it as hundreds of sieves, all stacked on top of one another. If you dump dirty water through this stack of sieves, the water won’t just pour right through, it’s going to slowly trickle through and be cleaned as it passes through. As it trickles, more stuff gets trapped. But it’s this trickling that highlights one of a HEPA filter’s biggest drawbacks. HEPA filters can drastically slow down the air passing through them. So vacuum cleaner motors have to be more powerful to compensate. It also makes a true HEPA filter unsuitable for use in a forced air central heat or air conditioning system. So filters for these systems have to be designed differently and thus, use a different rating.