If any bacteria, viruses or other pathogens are already "hanging out" in the atmosphere of a room, then the task of removing them with the help of a filter is almost impossible. We can only pass a small portion of the air through the filter at a time. The rest of the air is constantly mixed with each other and therefore, when filtered, the concentration of micro-pollutants decreases very slowly on an inverted logarithmic scale. In the presence of a source of pollution, such as a person coughing or sneezing, the situation with difficulty of air filtration worsens to a catastrophic level. Therefore, it is proposed to transform the room itself into a certain analogue of the electrostatic filter. In a way, by placing electrodes indoors and creating a sufficient potential difference, of course, within a safe power limit, we electrify all the microparticles in the air and they will quickly settle on one of the electrodes. Importantly! It should be the process of electrostatic charging and not ionization.
Therefore, it will be almost absolutely safe for people in the middle of such a room. In order for the micro-pollution deposition process to occur as quickly as possible, it is suggested to periodically spray fine mist of water vapor. For example, place one of the electrodes under the ceiling in the same place to spray micro droplets of water. Then the charged droplets will quickly fall to the floor on the room, taking down with them literally everything in the air. People who are in this area at this time, such as the station lobby, will not feel any discomfort. For them, staying in such a location will resemble the situation "in the park immediately after a thunderstorm". If among the people will be carriers of pathogenic viruses, then all these viruses will instantly settle contained on the floor without the threat of getting into someone's lungs. The electrostatic field generator can be the Van de Graaf generator, or further modifications thereof. It will be very inexpensive in mass production (several plastic stamped parts), energy efficient (small electric motor) and extremely easy to install and operate. One of the electrodes will be the floor of the room itself, and the second electrode is suspended sheet of plastic with a wire "hedgehog" in the middle of the sheet, suspended on the ceiling of the room. Air humidifiers, which, if necessary (!), Will raise the intensity of the filter - virtually any standard humidifier. Due to the simplicity of the construction and the ease of installation, such a micropollutant precipitatior can be mounted by any qualified worker or electrician. In the case of sanitary treatment of the device, all its parts can be treated with almost any detergent. If necessary, you can add an electronic control unit that will monitor the operation of the proposed device. And once again the most important thing is that the process of electrostatic charging and not of ionization should take place.
Let's consider the waiting room of a train station for 100 people. According to sanitary standards, the station's internal ventilation should provide them with an air exchange rate of 30 cubic meters of fresh air per person per hour. In our case, this would mean a total flow of 3,000 cubic meters per hour, equivalent to 50 cubic meters per minute or 0.833 cubic meters per second.
According to sanitary standards, the relative humidity should be in the range of 30-60%. Suppose natural humidity is 40% and we raise it to 50%. That is, our humidification of the air will work under comfortable conditions. For a warm season, a relative humidity of 100% means that there are more than 22 grams of water per cubic meter of air. That is, our 10% increase in humidity means that we only spray little over 2 grams of water every second.
Practical use of sprayers shows that spraying water into fine mist of droplets at a diameter of 1 micron (ie 1.0 E-6 m) is technically simple and energy-efficient. So, if you take a drop with a diameter of 1.0E-6m. then its volume will be approximately equal
V = ¾ * 3.14 * (0.5E-6)^3 = ~ 0.3E-18 cubic meters.
and the weight, respectively,
M = ~ 3.0E-14 kg
We have, as already said, sprayed 2 grams of water per second. This means that when spraying water into drops of 1 micron, we will be getting large amount of them every second, specifically:
N = ~ 6.7E12 microdroplets.
From the experience of operating the Chizhevsky chandelier, air ionizers, electrostatic filters, the current at the electrodes of the device is limited to the level of milli or microamperes. Let us have a current equal to 1 microampere (1E-6 A). Then a charge of 1 microcoulomb will flow into the electrode in 1 second.
The electron charge is = ~ = −1.6E-19 C,
Which in turn means that 1 coulomb is essentially 6.25E18 electrons.
That is, in 1 second, at a current of 1 microampere, 6.25E12 electrons per electrode.
At the same time, we sprayed about 6.7E12 drops of water. Which charged an average of 1 electron per drop. Which is a very realistic indicator - the mass of the droplet = ~ = 3.0E-14 kilograms, and the mass of the water molecule = ~ = 3.0E-26 kilograms, respectively, charge 1 additional electron at = ~ = 1.000.000.000.000 atoms - nothing extraordinary.
Now another aspect. The 100-passenger hall will have an area of 200 square meters. Let's imagine that our micro droplets are distributed throughout the hall area. We have 6.7E12 drops per 200 square meters, or 3.35E6 drops per square millimetre, or 3.35 drops per square micrometer. The droplet itself has a diameter of a micrometer. This means that within a few seconds, the entire volume of the waiting room is "combed" with micro-droplets between which no other droplet or dust can slip.