When we talk about cleaning we cannot avoid mentioning vacuum cleaners, and therefore their filters. There are different types available to meet the most specific needs. This is why it is a very important element to evaluate before buying a vacuum cleaner. We want to be of help and we have chosen to focus on the HEPA filter to understand what it is and why you may need it.
- Filtration
- What is a HEPA filter?
- How a HEPA filter is made and how it works
- Why you may need a HEPA filter for your vacuum cleaner
Filtration
We prefer to start from the basics. So, after seeing what a vacuum cleaner is and how it works, let’s deepen the knowledge of the filtration stage. We can divide the filtration into two phases: the inlet and the outlet phase. Consequently, vacuums have two types of filters:
- Primary filters, also called main filters, which have the task of retaining most of the particles and material present in the vacuumed air.
- Secondary filters, also called outlet filters. They have the task of stopping even smaller particles that have not been stopped by the primary filter in order to return pollutant-free air to the environment.
HEPA filters are often positioned at the air outlet of the vacuum cleaner, therefore they are considered secondary filters. But it is important to remember that in some vacuum cleaners they can also be positioned as primary filters.
What is a HEPA filter?
HEPA is the acronym for High Efficiency Particulate Air, which is a mechanical filtration system. This type of filter was developed by nuclear scientists to help remove radioactive particles. Subsequently, HEPA filters were used for many applications including for vacuum cleaners, both domestic and professional. They are chosen for their extraordinary filtration efficiency, which is why they are also called absolute filters. In fact, they have the ability to capture very small particles – up to 0.3 µm (micrometers). To better understand what we are talking about, here are some examples:
- Human hair: 50 – 70 µm
- Fine sand: 90 µm
- PM10: particulate consisting of particles with dimensions smaller than 10 µm
- Red blood cell: 7 µm
- PM2,5: fine particulate with diameter of less than 2,5 µm
- Bacteria: 0,2 -5 µm
- Viruses: 0,01 -0,3 µm
HEPA Filter Classification
There are specific rules for the classification of HEPA filters. At the European level, the EN1822 standard requires HEPA filters to remove 99.995% of particles. While in the United States the MIL-STD-282 standard requires that they remove 99.997%.
Still on the classification of filters, and following the European legislation, we remember that if they capture less than 85% of the particles they are called EPA filters (Efficient Particulate Air Filter). While filters that capture more than 99.999% of particles are called ULPA (Ultra Low Penetration Air Filter).
It is important to remember that HEPA filters are divided into other categories based on their filtration capacity. The HEPA filters available for Comac professional vacuum cleaners are H14 class and therefore have a filtration percentage that reaches 99.995%.
How a HEPA filter is made and how it works
A modern HEPA filter consists of a sequence of glass microfiber layers. These interlaced filaments are assembled in order to twist them in different directions and create a kind of fibrous tissue.
The operation of a HEPA filter is different than that of a standard filter, which normally holds particles as if it is a sieve. In fact, when the particles pass through the HEPA filter they are retained in different ways, also based on the speed of the air that carries them. We can identify these ways in four effects, which work together and synergistically to make filtration effective:
- Sieve effect: when the particles are larger than the distance between the fibers and therefore remain stuck in the first filaments.
- Inertial mass effect: when the inertia of the particles does not allow them to follow the air flow around the filter fibers. So, particles move along their path until they collide with one of the fibers, remaining attached to it.
- Interception effect: when particles, which are smaller than those retained by sieve or inertial effect, continue to follow the air flow until they touch the surface of the fibers and remain retained by the fabric.
- Diffusion effect: when the smallest particles do not follow the air flow but spread with a random fluctuations called Brownian motion. During this movement they can be held by the fibrous tissue of the filter. The slower the flow, the more likely it is for particles to hit a fiber and be held back.
Why you may need a HEPA filter for your vacuum cleaner
The HEPA filter installed on a vacuum cleaner is used to capture even particles invisible to the human eye such as mites, molds, pollen, spores, allergens and bacteria. So, in addition to dust, a vacuum cleaner with a HEPA filter is able to retain allergens, which are the most frequent triggers for asthma and allergy sufferers.
We often think that air pollution is something that only affects outdoor environments. Instead, even the air inside indoor spaces such as offices, homes and companies can be polluted. The extraordinary filtration efficiency of HEPA filters helps to retain most of the particles present in the environments where we live making the air we breathe better. This is the main reason why you may need a HEPA filter for your vacuum cleaner.
We hope we have answered most of the questions about HEPA filters. As always, if you have any doubts or want to know which Comac filters are available for vacuum cleaners, we are happy to help you. You only have to contact us!
This post is also available in: Italian