Forewarned is forearmed. Part 2

• Part 1: photosynthesis, all living things breathe, shock measurements .
• Part 2: room ventilation, damage to the assembly, the advantage of two instruments for conducting experiments.
• Part 3: graphics, calibration, analysis of the device, the principle of operation, fermentation .

The more people, the less oxygen

Air is a delicate matter, in which carbon dioxide is only fourth in quantity, but is essential for all living things. By the concentration of carbon dioxide, which is determined relatively easily, one can indirectly judge the content of other substances and use it for air quality analysis.

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The concentration of carbon dioxide is measured in prop - mills - parts per million ppm (ppmv), milligrams per cubic meter or percent.



To “swim” in terms of the concentration of carbon dioxide, you can read any article on the provision of air exchange, an example of “How much air does a person need for comfort?”



With increased carbon dioxide content, a person experiences breathing problems (stuffiness, asphyxiation, oxygen deficiency, lack of air), rapid pulse, fatigue, fatigue, headache, dizziness, drowsiness, inability to concentrate, loss of attention, decreased performance, irritability, fainting ( although he no longer feels it), etc. - fortunately, not all the symptoms are immediately, and not by every person.



The saying about the number of people / oxygen is relevant when people are in a closed room - they absorb oxygen, and emit carbon dioxide and other substances. Therefore, it is necessary to control the carbon dioxide content in each room where people are located.

Old age begins when more money is spent on maintaining health than on destroying it.

Interesting people who often complain about their health, give a lot of money to doctors and pharmacists, but do not try to create living conditions such that the ailment retreats automatically, without developing serious consequences.

To do this, quite a bit - in addition to genes (there is nothing to change), to obtain high-quality and in sufficient quantities of light, air, water, food, to lead a healthy lifestyle.



A person spends much of his life in confined spaces, where what he breathes is relevant.

Measuring the concentration of carbon dioxide is the easiest and most affordable way to control air quality, and therefore, if necessary, desire and small efforts to make it better, which will affect human health. The earlier in age to start doing this, the later the destruction of the body will begin.



Breathe good air in the room energy-efficiently. But it is better to give money to energy companies than to doctors, after all, only treatment is more expensive than health.



To replenish the room with air with a high oxygen content, it is necessary to draw out the exhaust air with a high content of carbon dioxide and other substances. From here there are simple requirements:

1. The room must have sufficient volume so that a person always has enough than to breathe. Therefore, when buying a home, it is desirable to consider not only square meters, but also cubic.

2. It is necessary to ensure both the air flow and its outflow. In the absence of one or the other, the process of air replacement takes a long time and does not keep pace with the increase in carbon dioxide concentration.

Example. In the old houses everything was done very well - fresh air was evenly supplied through the gaps in the windows and doors, and the removal of the exhaust air through the exhaust ventilation in the toilet. After installing modern sealed windows and doors, the person sharply limited not only the supply of fresh air, but also the outflow of waste. The inlet valves help, but they deliver air locally, compared to even distribution from the slots of the old window.

Natural or active ventilation should provide such an air exchange that at any time in the presence of a different number of people the content of oxygen, carbon dioxide and many other components of the air is always within comfortable limits.

3. In winter, it is possible to provide heated air. The simplest option is to install a supply valve between the window sill and the heating radiator (a modern analogue of the slot). In order not to throw out the heat with the air leaving the room, recovery systems can be used when the outgoing stream heats the incoming air.

4. The carbon dioxide sensor allows you to turn on the ventilation and adjust its performance in automatic mode so that energy is spent only in the presence of a person when the concentration of carbon dioxide increases.

5. About the dangers of air conditioning. In addition to the cold air flow, often falling on people's heads, the temperature difference when going outside, bacteria that live comfortably in the cool, there is a danger that is rarely mentioned. In order to save electricity, when the air conditioner is closed, all windows are closed. At the same time, the concentration of carbon dioxide quickly reaches a considerable value and produces cool, but oxygen-poor air. Therefore, the window must be kept open - health is more expensive.

Since we introduced a tax on the air, you breathe less, outrageous!

In our country, the tax has not yet been introduced? But everything is possible. Therefore, it is necessary to fight for it to be fair, and we would pay money not “for the air” but “for the clean air”. One of the instruments for monitoring the state of the air is a measuring instrument for the concentration of carbon dioxide.



Air does not meet the norm, respectively, and the tax should be less.



If you equip all kindergartens, schools and workplaces with such devices, you see, and something will change. After all, with high-quality air and excellent health, a person breathes less often (tax reduction), and thinks better.

There is a lie, a blatant lie and statistics

At work, about as well - there is a comfortable working day, a difficult and meeting.







Day 1. On a comfortable day, the window is always ajar and labor productivity is high even for two people. The Cabinet has a volume of 6.07 x 2.9 x 2.88 = 50.7 m3. 50.7 m3 / 2 = 25.35 m3 per person.

Day 2. On a difficult day, for the sake of science, as an experiment, the window was closed for the whole day - a typical situation for many employees who also glue all the gaps in the windows. This time, a work colleague, under various pretexts, ran from the experiment to the neighboring rooms, and for the most part of the time it took a puff (literally) alone, so one employee had 25.35 m3 and 50.7 m3. At the time of the arrival of two more colleagues (50.7 / 4 = 12.7 m3 / person), it was possible to achieve a carbon dioxide concentration of 1742 ppm - on the graph, the peak “Give air”. What is interesting, people who came from the street for a short time did not make any complaints about the lack of air, and it was hard in the past. Each opening of the door upon leaving the room or returning filled the room with life-giving oxygen (removed carbon dioxide) and became a little easier. On a more detailed graph, it was clear that with each return to the office there was a surge in concentration. Apparently, the air in the lower part of the room with a tightly closed door has a higher concentration of carbon dioxide, and when a person moves from the door, he rises to the top and covers the device on the table. Then, gradually it descends, occupying its usual place - the wave of increased concentration subsides.



The graph also clearly shows the time of the start / end of the working day and lunch break.







In general, the performance on a difficult day was low, after dinner I wanted to sleep, I was looking forward to the end of the working day.



The absolute majority of people live and work in an environment that was on the second day, justifying it by the absence of drafts, protection from the penetration of cold air (in winter) and the fear of catching cold. Perhaps they are getting used to and working productively, but this atmosphere is not for me. It is especially difficult when the high content of carbon dioxide lasts for a long time.



Day 3. The window is again ajar, there is one person in the room and the concentration level is lower than it was on the first comfortable day.



Now about the meeting .



With a room size of 12 x 6 x 2.8 = 201.6 m3 and 28 people, 7.2 m3 of air per employee (imagine yourself in a cube with a side of 1.93 m). In this regard, it is interesting to see the requirements for the systems of cleaning and ventilation of air in submarines and space ships.



The meeting was well ventilated before the meeting. People arrived in advance and the concentration with a comfortable 435 ppm began to grow. As always, someone was cool, the window was closed ...



After 6 minutes after the start of the meeting, the level of 1200 ppm was exceeded, after 29 minutes - 2000 ppm, and after 68 minutes, the ceiling of the instrument's working range of 3000 ppm was “pierced”. The letters “Hi” lit up on the indicator, the device did not react to anything. The meeting lasted 1 hour and 43 minutes, after which the people parted, the window and door were reopened, but the indicator was still in the beyond state for another 3 minutes. Only 60 minutes later the level dropped to 500 ppm.

Saved by the fact that the meeting did not last a whole working day.



Therefore, who wants to breathe less carbon dioxide and appreciates his time just as David Grady - listen to the call of Vladimir Mayakovsky from the poem "Prosat."

As soon as you find your soul mate, other halves begin to roam around and make you doubt, therefore - you must hesitate confidently

So that there is no doubt that all the halves have similar characteristics, two gauges took part in the testing,







who were asked questions about carbon dioxide







And about the temperature. The answers were close to ideal, where the readings of an already shabby, home-made device based on the SHT75 sensor were used as the ideal temperature (the one who floated knows that).







In the video “Starting the CO2 meter”, you can observe the process of “setting up” the values, and it is quite possible - the rarest footage of the automatic calibration work. This is not a comparison with similar devices, but a struggle with one’s own kind.







For the final verification of the similarity of indications, an experiment was carried out with the package when two devices were placed in one closed space. For the purity of the experiment, in order to eliminate the influence of the possibly activated automatic calibration of the “8bC” mode sensor, especially after photosynthesis with artificial lighting, when the concentration decreased to 293 ppm, a preliminary reset to the factory settings was performed.



After 30 minutes of being in the package, only a slight difference was recorded, which is a good indicator for a household appliance.







Two test instruments made it possible to conduct experiments to measure concentration simultaneously in different parts of the room.



Comparison window and table.

The window is an old window with good slots, through which fresh, uncharged air enters the room and “washes” the device mounted on the window sill. The graph does not rise above 500 ppm and responds poorly to indoor processes.







People are drawn to the window not only to gawk - they want to breathe fresh air from the cracks. Now most of the windows are plastic and wind-proof, and the habit of approaching the window still remains.



On the table, located a couple of meters from the window, the graph is too nervous - it responds to everything, although the sensor is located so that it does not get breath exhaust.







Comparison top - bottom.

Sensors are located in one place of the room. Bottom - on the floor, top - at a height of 2.2 meters (cable length no longer allows).

Since the window has a gap, the fresh cold air that enters the room creeps to the bottom. As a result, the graph of the lower sensor is more direct,







than the top.







The protrusion on the upper graph is caused by the fact that at this moment a photographing of the method for installing the sensor using a cable duct was made.







Instrument readings at different heights depend not only on the accuracy of the sensor, the presence of people and their activity.

In many rooms, particularly here, the windows are not hermetic and have good slots. The door is also not perfect. If the door is very tightly closed, there is no draft. But costing to leave the slightest gap, then begins the movement of air from the window to the door. The door leaf has a size of 2000 x 800 mm. We believe that from the hinge side with a small opening of the door the air does not pass. With a gap of 1 mm, the opening for the movement of air has an area of ​​2800 mm2 - this is a square with a side of 53 mm. For a gap of 2 mm - a square with a side of 75 mm, for 3 mm - 92 mm, for 5 - 118 mm.



The wind direction is also important. If he blows through the window, the air exchange rate increases.



Thus, when drafted in winter conditions, when fresh cold air enters the room, it spreads low and the concentration of carbon dioxide is lower there.



If the room is sealed, then the concentration in the lower part of the room in the presence of people increased. Carbon dioxide is highly soluble in air, but it is heavier than air .

Close the window, blowing!

There is almost always a person in the team who “blows” to. This may be due to the nature of the character, health, improper location of the workplace, unsuccessful room layout, errors in the design or installation of ventilation and air conditioning systems.

We do not have such, so you can safely work with the window ajar and apply extreme airing.

At a height of 2, 2 meters, the ventilation chart looks like this







On the floor, he is:







Ideas for use.

1. The MT8057 device can be used in automation systems even without opening it. To connect just one / two / three photocells, which are installed opposite the “traffic light” of the device. This opportunity is a big advantage of the model in comparison with those that are equipped only with LCD indicator. Thresholds for turning on / off the signal LEDs are configured in the device, so you can implement various ventilation or window control algorithms. In this direction, you can use any of the electronic platforms that have mastered the radio amateur. Beginners can easily implement the simplest set-top box for the device to control the ventilation system or a signaling device.

You can transmit a signal to the control device by wire or by radio.

2. Savings on ventilation costs.

In addition to automating the activation of ventilation and performance adjustment with a carbon dioxide sensor, energy consumption can be further reduced. To ensure a healthy sleep and not to ventilate the whole apartment, it is enough to reduce the ventilated volume to one room and even less when using a canopy over the bed.

3. Breathe like birds in the forest.

Not every city dweller can breathe pure forest air. Even a gardener does not always work among trees.

Not at all, but there may be situations when the intake of clean and fresh air for fresh air can be organized directly from the crown of the tree, if it is located at an accessible distance from the house. Now we know why we need to build a house, raise a son and plant a tree. If the ancestors of a man got down from a tree, then modern people again aspire to sources .

4. Carbon dioxide concentration indicator can be used in security systems. It is easy to determine the presence of a person, the number of people and physical activity. If there is a person, the opening of a door or windows is fixed.



A lot of photos - instructions for working with the device and its main technical characteristics, measurement results, printed circuit board and work schedules are given in the album “ Carbon Dioxide Meter ”.



Reference to the acquisition, software for connecting to a computer, description and technical characteristics of the carbon dioxide detector MT8057.



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