Filtration design was maximized by using the following filtration principles
1. Interception – Occurs when a dust particle follows the air streamlines, but still comes in contact with the yarn (fabric) as it passes around it. If the forces of attraction between the yarn and the dust particle are stronger than the tendency of the airflow to dislodge it, the particle will be removed from the air stream.
2. Diffusional Effect- As the dust-laden air passes through the filter media, minute particles do not precisely follow the streamlines. Instead, they are bombarded by air molecules which cause them to take an erratic path. This erratic path increases the probability that the particles will come in contact with the yarn and stay attached. This can reduce the spread of viruses and other micro-organisms.
3. Straining – Occurs when the smallest dimension of dust particles is greater than the distance between the woven yarns. This can reduce the spread of viruses and other micro-organisms.
4. Impingement- As the dust-laden air passes through the filter media, the air tends to pass around the filter fabric. However, due to inertia, the dust particles do not follow the air stream and collide with the filter media. This causes the particle to fall out of the airstream or attach to the media allowing for less spreading of the most common airborne viruses and micro-organisms.
5. Collision Probability – This factor relates to the design of the filter media. It allows for the maximum number of opportunities for impingement to occur in the filter. The layering of our filter was done to maximize this effect while we still looked at the effect on pressure drop.