What is air filtration?
An air filter has the primary task to filter particulate matter from sucked-in air. That will create a comfortable indoor climate and decrease the risk of spreading virus particles.
4 ways to trap solid dust particles
There are two types of dust particles, which are solid and gaseous. However, how to trap solid or gaseous dust particles is different. In this blog, the focus is on solid dust particles.
There is a large diversity of air filters with different features and quality. However, the principle of air filtration is the same. The sucked-in air enters the air filter from one side and comes out clean from the other side. Nevertheless, what exactly happens within the air filter is not always clear.
Solid dust particles can be captured in four different ways. We explain these four methods separately from each other below. There is the sieve effect, the inertia mass effect (collision principle), the diffusion effect, and the interception effect.
The sieve and inertia-mass effect
The sieve effect
One of the most applied and easy filter techniques is the so-called sieve effect. A dust particle is taken through an air duct by the airflow. Then, the particle reaches the filter media and is too large to pass through the media fibres. The dust particle is therefore held back and remains behind in the air filter. That is the same principle as if you are going to sieve a flower. The delicate flower goes through the sieve, and the residual peelings remain behind in the sieve.
The inertia-mass effect (collision principle)
For bigger dust particles, the inertia-mass effect works the best. The dust particle is blown into the filter by the airflow. The air then reaches the fibres and bends nicely around them. When the bigger dust particle has reached the fibres, this one, on the other hand, follows a straight path and collides, as it were, with the fibres. Thus, the dust particle remains behind in the filter, and the air passes through the filter.
The sieve effect
One of the most applied and easy filter techniques is the so-called sieve effect. A dust particle is taken through an air duct by the airflow. Then, the particle reaches the filter media and is too large to pass through the media fibres. The dust particle is therefore held back and remains behind in the air filter. That is the same principle as if you are going to sieve a flower. The delicate flower goes through the sieve, and the residual peelings remain behind in the sieve.
The inertia-mass effect (collision principle)
For bigger dust particles, the inertia-mass effect works the best. The dust particle is blown into the filter by the airflow. The air then reaches the fibres and bends nicely around them. When the bigger dust particle has reached the fibres, this one, on the other hand, follows a straight path and collides, as it were, with the fibres. Thus, the dust particle remains behind in the filter, and the air passes through the filter.
The diffusion and interception effect
The diffusion effect
The smaller dust particles are possible to capture with the means of the diffusion effect. Because the dust particles are so small, slight changes can interrupt the path of the dust particle. Hence, the dust particles do not follow an airflow but instead move between the airflows (Brownian motion) and can be compared with a gaseous particle. Due to the irregular movements of the dust particles, there is a very high probability that they will collide with the fibre and thus be trapped.
The interception effect
The last way to trap dust particles is by the means of the interception effect. This method is used only with synthetic media because of the electrostatic force. The dust particles follow the airflow in the usual way. When the dust particle approaches a fibre, it is pulled towards it by electrostatic force. Then, the dust particles remain stuck to the fibre and are therefore trapped.
The diffusion effect
The smaller dust particles are possible to capture with the means of the diffusion effect. Because the dust particles are so small, slight changes can interrupt the path of the dust particle. Hence, the dust particles do not follow an airflow but instead move between the airflows (Brownian motion) and can be compared with a gaseous particle. Due to the irregular movements of the dust particles, there is a very high probability that they will collide with the fibre and thus be trapped.
The interception effect
The last way to trap dust particles is by the means of the interception effect. This method is used only with synthetic media because of the electrostatic force. The dust particles follow the airflow in the usual way. When the dust particle approaches a fibre, it is pulled towards it by electrostatic force. Then, the dust particles remain stuck to the fibre and are therefore trapped.
Efficiency
An air filter consists, of course, of thousands of these fibres. That allows it to capture a large number of dust particles. The actual efficiency of the filter can fluctuate during its lifetime. Thus, some filters work better if some dust has already been captured. The different methods can be applied in one air filter as well. This combined effect ensures overall efficiency.
Written by Elmo
Marketing Manager at Tops Luftfilter