Increasing CO2 concentration in the atmosphere has led to a "global greening" effect. When stuffy: stuffy room and hypercapnia Lethal concentration of co2 in ppm

As you know, the cause of many health problems and chronic fatigue syndrome can be an excess of carbon dioxide (CO2) in the room air (). Saves from this airing and ventilation. In order to understand how well my apartment is ventilated, I bought a device that measures the level of carbon dioxide in the air - a CO2 monitor. I took a model with a data logger, it is very convenient to watch how the CO2 level changes during the day.

Over the past 50 years, the concentration of carbon dioxide in the earth's atmosphere has increased from 0.0315% or 315 ppm to 400 ppm and is growing by 2.2 ppm per year. The concentration of CO2 almost does not depend on the place on earth - the air mixes well. Surprisingly, the CO2 content in urban air and in the forest differs by only 10 ppm. It is believed that a concentration of up to 700 ppm is not noticeable to a person and does not affect his health and well-being in any way.

A person releases a lot of carbon dioxide when breathing, so in a closed room the concentration of CO2 rises very quickly to 2000 ppm and above.

There are two methods for determining the concentration of carbon dioxide in the air - electrochemical (solid electrolyte) and the method of non-dispersive infrared spectrometry (Non-dispersive infrared (NDIR) technology). The electrochemical method is less accurate and the sensors based on it are short-lived.

There seem to be only two manufacturers of NDIR sensors. Better known is the Swedish SenseAir http://senseair.com. SenseAir is now releasing the K30 sensors. The previous generation SensAir K22 sensors have been discontinued, but many have been made and are now sold relatively cheaply, allowing CO2 meters to be made for as low as $100.

It is with such a sensor, SensAir K22, that the AZ Instruments 7798 CO2 datalogger is equipped. For unknown reasons, when this device is sold under the original name, it costs as much as $390, however, the cunning GainExpress seller on Aliexpress and Ebay sells the same device under the name "CO98 3-in1 CO2 Carbon Dioxide Desktop Datalogger Monitor Indoor Air Quality Temperature Relative Humidity RH 0~9999ppm Clock" for $139. That's where I bought it.

A similar device without a datalogger and with a less accurate humidity sensor from the same seller costs $119.

Included - device, power supply, USB cable, CD with the program, instructions, calibration certificate.

The device shows the level of CO2 in ppm, temperature and humidity with high accuracy, time and date. In addition, the estimated status of the carbon dioxide level is shown - Good, Normal or Poor. If desired, upon reaching the Poor level, the device may start beeping and show the fan icon - it's time to ventilate.

This instrument uses an accurate capacitive humidity sensor (±3%RH at 25°C, 10~90% RH, ±5%RH at 25°C,<10% & >90%RH). Cheaper CO2 meters have simpler sensors that give more error at low humidity levels.

The device can show the minimum and maximum values ​​of all three measured parameters. In the data logging mode, the frequency of measurements is set (from 1 second to 5 hours). A long press on the Log button starts recording the values ​​in memory. During recording, the LED and the main display flash (ppm value constantly changes to rec). Because of this blinking, it is inconvenient to constantly leave the device in logging mode. the recording ends by long pressing Esc. Each new entry erases the previous one.

After recording is completed, the data can be transferred to a computer. To do this, the device has a small round connector on the back, and a USB cable is included.

The program reads data from the device and draws graphs like this.

You can turn on the display of temperature and humidity, but then the screen will be such a mess.

The NDIR sensor requires periodic calibration, so the instrument is automatically calibrated once every 7 days. The minimum value of CO2 is taken as 400 ppm (at the same time, the calibration can shift the readings by no more than 50 ppm at a time). For proper operation of the device, it is necessary to ventilate the room at least once a week (3-4 hours with an open window without people in the room). This is enough for the CO2 level in the room to become the same as outside and the device to calibrate correctly.

The device is powered only from the mains. This is due to the fact that the NDIR sensor consumes quite a lot. The device constantly consumes 30 mA, once per second there is a consumption pulse of 200 mA. The supply voltage is 5 volts. I used the power bank to temporarily use the device as a portable device, measuring CO2 levels in different rooms.

The presence of this device not only allows you to assess the level of CO2, but also greatly stimulates the correct and frequent ventilation - you look at the "terrible" readings of the device and immediately run to open the window.

Despite the fact that the device is not cheap, I ordered a second different model so that there would be a CO2 meter in each room. When it arrives, I'll tell you about it.

Most of us spend a lot of time at work in offices, soldering iron workshops, and other enclosed spaces where there is often no natural ventilation. Especially the situation with the supply of fresh air from the outside has worsened in recent years with the widespread arrival of plastic windows, which practically "do not breathe". In rooms where people are located, there is always some part of the carbon dioxide (CO 2) that a person exhales. And if the room is not periodically ventilated, then its concentration gradually increases.

The concentration of CO 2 (carbon dioxide) is measured in ppm (ppm). Outside the city and in rural areas, the concentration of carbon dioxide is usually 350 ppm, in the city 400 ppm, in the city center 450 ppm. The figures vary greatly and depend on traffic density, wind strength and other factors. For example, in Moscow, on busy highways, the level of CO 2 can reach 800-900 ppm.

With a high concentration of carbon dioxide, a person develops discomfort, headaches, sleepiness, nausea, and other symptoms. The danger is that the threshold of deterioration is sometimes very difficult to notice and this value is individual for each person. Therefore, in order to maintain normal health in the room, it is important not to exceed the CO 2 concentration threshold, which is approximately 800-900 ppm. On average, one person for 3 hours in a closed room of 20 sq.m raises the level of carbon dioxide concentration to 1500 ppm. And if there are three people, then in just 1 hour.

There are several methods for measuring carbon dioxide concentration. In portable devices, the NDIR method of non-dispersive infrared spectrometry has become widespread. An NDIR sensor is a spectrometer that measures the absorption of light of a single wavelength as a function of the concentration of the gas being measured. For carbon dioxide, an IR LED with a wavelength of 4 µm is used.

Until recently, CO 2 meters were too expensive for home use. Worldwide manufacturers of household CO meters 2 can be counted on fingers. But nevertheless, they are and are already being sold with might and main on AliExpress and eBay: CO2 Monitor . True, the cost of even the simplest models starts at $100, and more or less worthy devices start at $200. Many of them use the NDIR method for measuring carbon dioxide.

Not so long ago, an inexpensive solution "Carbon dioxide detector" from the MasterKit company, widely known in amateur radio circles, appeared on the domestic market. This material is devoted to a small review of this meter. Like all products from MasterKit, this meter has its own unique code - MT8057.

Device characteristics:

The detector is packed in the following box:

The reverse side provides information on carbon dioxide and its levels in the premises.

The country of manufacture of the device is China. Looking ahead, I’ll let you know that I googled two devices outwardly almost completely identical to the monitored one:
- ZGm053U
- CO2mini RAD-0301

The cost of the first device is not indicated on the site, and the second device costs $ 100, excluding shipping costs. For the device from MasterKit, I gave 3400 rubles. together with delivery (data as of the end of January 2015). Today, I think you can hardly find a similar device anywhere at a lower or similar price.

The box contains the meter itself, a USB cable and instructions in Russian.

Retrieve the meter:

On the front of the meter, we see a screen for displaying CO 2 levels and temperature, as well as three LED indicators: green, orange and red for threshold indication. In my opinion, this is a very good solution - a simple glance (especially in the evening or at night) is enough for a quick assessment of the level of CO 2 concentration. After a week of operation of the device, I noted for myself that, first of all, I pay attention to these indicators, and not to the numbers on the device screen. In the device settings for each LED, you can set CO 2 levels.

It is also a good option for constructing DIY devices, for example, for controlling supply ventilation, domestic ventilators and other climate equipment. You can solder to the LEDs or use photoresistors (or photodiodes) by placing them opposite the meter's LEDs. By setting the LED turn-on levels, you can turn the supply ventilation on or off when a certain threshold is reached. This can be substantially cheaper than a separate CO 2 measurement module.

On the back of the device there is a sticker with the name, brief characteristics and serial number, as well as 2 buttons for settings.

When I ordered the meter, to be honest, I expected a larger device. But p The device turned out to be quite compact.

Weight was 64 g.

Dimensions: 116*38*23.8mm

The data on the display is read quite clearly. CO 2 and temperature readings:

The device is powered by a 5V USB bus. Cable - microUSB. There is a recess on the body of the device for the USB connector, which is why not every micro-USB cable can be connected. In any case, out of the 3 cables I have, none of them went in completely. Therefore, you need to be careful with your native cable and not lose it, otherwise you will then have to think about how to connect it to a regular normal cable.

Battery power is not provided, which upset me a little. For offline use, you will have to use a Power Bank with a USB output.

Opening the back cover gives access to the insides of the device.

A long element with a sticker "ZGm053UK" is the heart of the device - an NDIR carbon dioxide concentration sensor. In the video below, you can see how the measurement lamp flashes. The flash rate is approximately 1 flash every 5 seconds.

As can be seen from the oscillogram above, the voltage to the lamp is 5 volts.

The pulse shape for the lamp is increasing, apparently to extend the life of the lamp. The pulse duration is approximately 300 ms.

Build quality and soldering are quite good.

A legitimate question may arise about the duration of the sensor. The manufacturer ZyAura can find the answer on this page:

How long is the NDIR life?
We use dual channel(beam) NDIR (Non-Dispersive Infrared), thermopile from PerkinElmer, whichimproves the long-term stability of the measurement; it has longer durability than single channel design so the device has a durable life more than 5~10 years.

Those. The lifetime of the sensor is 5-10 years. The sensor needs to be calibrated approximately every three years.

For meters, there is a special software for displaying graphs, as well as for calibration. You can download the software on this page. Don't forget to rename the ZG.eye file to ZG.exe after downloading. Why they did this is incomprehensible, especially considering that everything is in the archive.

The yellow line in the graph above is the temperature (scale on the right). Bottom line - CO 2 level.
Room approximately 12 sq.m. 1 person. Plastic windows. At about 2:35 p.m., the window was opened. As can be seen from the graph, the temperature began to fall, and after it, the CO2 level immediately began to drop to an acceptable value, after 10 minutes completely moving into a safe (green on the graph) zone. At about 2:50 pm the window was closed and the temperature and CO 2 began to rise gradually.

For Linux operating systems, there is also OpenSource software available on GitHub. Unfortunately, under the Debian OS, I could not compile the application, because constantly cursed at the lack of a package, although it was installed. But theoretically, this makes it possible to connect the meter via USB to various Linux microcomputers (Raspberry Pi, CubeBoard, BeagleBone) and control devices (via GPIO) or upload data to some server, use it for the Smart Home system, etc. .P. There are already a lot of possibilities here.

Whether you need a CO 2 meter or not - everyone will decide for himself, personally I don’t regret the money spent on it and I’m even thinking of buying a second one, one for home, one for the office where I work.

Pros of the MT8057 Carbon Dioxide Meter:

• Low price compared to similar devices
• The presence of a "traffic light" - three multi-colored indicators
• Using a modern NDIR sensor, not a chemical one
• Large time interval for calibration
• Connecting to a computer via USB for plotting
• Availability OpenSource software for Linux systems

Cons MT8057:

• No built-in power supply
• Non-standard recess in the case for the Micro-USB connector
• Low accuracy of 100ppm, but quite sufficient for home use
• I would also like to have a humidity sensor

Air is a mixture of gases, in which carbon dioxide (CO2) occupies only the fourth place in terms of quantity, but it is of the utmost importance for all living things. Measuring the concentration of carbon dioxide is quite easy, and data on the amount of CO2 allows you to indirectly judge the content of other substances and use this data for air quality analysis. The basic unit of measure for carbon dioxide concentration is ppm.

With a slight increase in CO2 levels, a person feels stuffiness, fatigue, drowsiness, inability to concentrate, loss of attention, irritability, decreased performance, etc.

In closed rooms with insufficient ventilation, a person actively absorbs oxygen (O2), while exhaling a large amount of carbon dioxide, and if a person is not very susceptible to changes in the oxygen content in the air, then changes in the CO2 content are felt by every cell (and this is not a metaphor) due to the fact that the process of gas exchange of O2 and CO2 in the lungs occurs due to passive diffusion through the cell membrane, and the diffusion capacity of CO2 is 25-30 times higher than that of O2, which is why a person is very sensitive to changes in the concentration of CO2 in the air.

It is also significant that gas exchange in cells proceeds normally only at the correct value of the partial pressure of CO2 in the blood (PA CO2). At the same time, both an increase and a decrease in PA CO2 leads to the fact that the transport of O2 to cells worsens, as well as to many other changes. A simple example: if you hold your breath, then the transport of O2 to the cells in the lungs worsens, but the transport of CO2 does not stop, while initially the desire to take a deep breath causes the increase in PA CO2. This is a protective function of the body - a command aimed at returning the level of PA CO2 to normal, a warning that something is not right. Similarly, the body behaves in stuffy rooms with high levels of CO2 - there is a desire to take a deep breath, open a window, go out to breathe on a balcony or street.

As you can see, the most harmful is a long-term stay in rooms with a high content of CO2, which is why special attention should be paid to home ventilation and ventilation of workplaces. At the same time, the most correct and energy-efficient method of air exchange regulation is regulation by a CO2 sensor.

The use of this method of regulation is also the most convenient for the user, since it is not necessary to click switches, turn the regulator, constantly adjusting the air exchange, and even more so switch speeds on the control panel. The user does not interfere with the operation of the ventilation system at all, the unit regulates everything automatically and as accurately as possible, creating an ideal atmosphere in the premises, regardless of constantly changing conditions.

CO2 sensor control options

Please note that there are two types of air exchange control based on the CO2 sensor.

Ventilation by one unit of several rooms

Ventilation of several isolated air volumes, such as apartments, houses, several offices. It is mainly used on the household equipment line CAPSULE and I-VENT, as well as on the supply and exhaust units ZENIT, ZENIT HECO. For each room we need:

• Proportional valve on the supply channel
• Proportional valve on the exhaust duct (If the hood is in each room)
• CO2 sensor for each room or exhaust duct for each room.
• VAV system on the unit (installed by the manufacturer).

When a person enters the room, the CO2 sensor will register an increase in CO2 levels. The motorized proportional valve will regulate the air exchange based on the readings of its own CO2 sensor. This control option will allow you to maintain the air quality in the room as accurately as possible, preventing a feeling of lack of air and without creating excessive air exchange.

An example of the operation of ventilation by CO2 sensors installed in the premises:

There is one person in room 2, and to compensate for the increase in CO2 concentration, it is enough to supply 25 m³/h to the room. In room 1, there are two people, and 75 m³/h must be supplied to compensate. If one person leaves the premises, then in room No. 2 CO2 emission will stop completely, the valve will close, and the ventilation of the room will stop. In room 1, CO2 emissions will decrease and the unit will gradually reduce the air exchange in room 1 to 25 m³/h.

ATTENTION!!!

The use of one CO2 sensor in the exhaust duct is undesirable if there are several rooms. The CO2 sensor will register the total concentration of carbon dioxide and increase the air exchange equally in both rooms. As a result, there is not enough air exchange in the upper room to compensate for the increase in CO2 levels, and an excess amount of air is supplied to the lower room.

Ventilation by one unit of one room

Ventilation of one isolated volume of air, e.g. office, gym, production room, studio apartment. In this case, we only need a CO2 sensor installed in the exhaust duct (installed by the manufacturer). The air exchange will be automatically adjusted to maintain the required level of CO2, regardless of the change in the number of people in the room, as well as their type of activity.

This control option is mainly used on the industrial line of equipment of the Zenit, Zenit HECO, CAPSULE series and even in i-Vent installations. The use of this system will allow organizing the most energy-efficient ventilation system, with minimal operating costs and fully automatic control.

Example of ventilation operation by CO2 sensors installed in the exhaust duct:

There is one person in the room, and to compensate for the increase in CO2 concentration, it is enough to supply 50 m³/h to the room, as the number of people in the room increases, the recorded level of CO2 increases, and the unit automatically increases the amount of air that needs to be supplied to the room to compensate for the increase in level CO2.

Calculation of the ventilation system for CO2

This is one of the options for calculating the ventilation system, but, unfortunately, it is used quite rarely, since there are not too many systems that can regulate air exchange using a CO2 sensor. To calculate nm, you need to know the following data:

1. Outdoor CO2 concentration.
2. Schedule of stay of people in serviced premises.
3. The type of physical activity in the serviced premises.
4. Required maintained CO2 level.

The formula for calculating the air exchange to compensate for the emission of CO2 by one person: L=(G×550)/(X2-X1)

• L - air exchange, m3/h;
• X1 - CO2 concentration in the outside (supply) air, ppm;
• X2 - allowable CO2 concentration in the room air, ppm;
• G is the amount of CO2 emitted by one person, l/h;
• 550 - conversion of X1 and X2 values ​​from ppm to g/m3.

Data for G and outdoor CO2 concentration are selected from tables.

An example of calculating an apartment with a number of residents of 3 people.

For these conditions, the Zenit-350 Heco unit will be most suitable.

If you make a schedule for the day, you will be able to see a picture of the change in air exchange during the day, depending on the release of CO2 in the apartment.

As we can see, even according to the average schedule, the schedule of changes in air exchange is very significant, in reality, the system constantly regulates air exchange, having practically no "shelves" on the schedule. At the same time, if the unit is chosen correctly, in this case it is Zenit-350 Heco, then the CO2 value in the apartment will always be unchanged.

*It does not matter for the calculation which type of CO2 unit control is used. This can be either a sensor in the exhaust duct, if it is the ventilation of a studio apartment, or room CO2 sensors together with

There are common truths that are familiar to any person almost from birth. It is cold in winter and warm in summer. Respiration consumes oxygen and releases carbon dioxide. When a lot of carbon dioxide accumulates in a room, it becomes stuffy, and in order to be more comfortable in the room, it needs to be ventilated. But at the same time, most people tend to underestimate the impact of increased CO2 concentration on health and quality of life. This is what I want to talk about in this article, and also show how the air conditioner affects the air purification process. And at the same time provide an overview of the CO2 level detector, which helps keep indoor air quality under control.

1 Things to know about CO2
2 Technical information
3 Appearance and principle of operation
4 measurements
5 Home automation
6 Conclusions

1. What you need to know about CO2

CO2 or carbon dioxide is an integral part of any air mixture, the content of which is measured in parts per million (ppm - parts per million). A conditionally normal level of CO2 in fresh outdoor air is considered to be 400ppm. This figure is not constant and depends on the specific location - for example, in an ecologically clean area with a lack of industry and a low population density, the carbon dioxide content in the atmosphere can be below the average value, and in a densely populated metropolis, and even with industrial enterprises, it will almost certainly be above average.

Indoor air is considered to be of good quality if its CO2 content fluctuates within 800ppm. When the concentration of carbon dioxide reaches 1000ppm, many people already have a feeling of stuffiness and lethargy, and 1400ppm is the normal limit according to the recommendations of San Pina.

A dangerous level is 30000ppm - when such a concentration of CO2 is reached, a person's pulse quickens, there is a feeling of nausea and other symptoms of oxygen starvation. The good news is that it is almost impossible to “breathe” such a concentration of carbon dioxide in office and residential premises, even of very poor quality. However, even small excesses of the permissible concentration of CO2 can significantly affect the quality of life. Already at 1000ppm, concentration of attention decreases, a feeling of lethargy appears, the brain begins to process information worse. With CO2 levels above 1400ppm in the office, it becomes difficult to concentrate at work, and at home there will be problems with sleep. The content of CO2 depends, to a greater extent, on the number of people in the enclosed space.

“You can only manage what you can measure,” wrote the founder of modern management theory, Peter Drucker. And the first step to managing the indoor microclimate is to start tracking its objective indicators.

Carbon dioxide sensors are an integral part of the building automation system and usually control forced ventilation and air conditioning. The adjustment of the supply and exhaust ventilation power previously had to be carried out in accordance with the established standards, which focused on the maximum design indicators, for example, on the required air exchange rate depending on the type and volume of the building.
An adaptive ventilation system controlled by CO2 sensors consumes 30 - 50% less energy compared to a constantly running forced ventilation system. After all, for the required volume of supplied and removed air, it can be much less than the calculated values. At the same time, the adaptive ventilation system, equipped with CO2 sensors, timely performs air exchange in the room when it is required, creating comfortable and safe conditions for life and work.

Why is carbon dioxide dangerous to humans?

The maximum allowable CO2 content in the air is only 700 ppm. If this threshold is exceeded by 2.5 times, people who breathe carbon dioxide-polluted air experience headaches and fatigue. Already after 6 hours of work in such conditions, concentration and efficiency are greatly reduced. At the same time, the CO2 content in a poorly ventilated room, where there are a large number of people, increases in arithmetic progression in a matter of minutes. For example, when about 20 people gather in a small meeting room (about 20 square meters), the concentration of carbon dioxide will rise to 10,000 ppm within an hour if fresh air is not supplied.

An increased concentration of CO2 negatively affects human health not only during the day, but also at night, even though all processes in the body slow down. Scientists from the Netherlands have found that air quality is more important than sleep duration for healthy sleep. Prolonged inhalation of air with a high content of carbon dioxide leads to a deterioration in immunity, the development of acute and chronic diseases of the upper respiratory tract, cardiovascular system, blood, etc.

When are carbon dioxide sensors needed?

CO2 sensors allow you to start ventilation, including emergency ventilation, and other utility systems.

Scope of application:

• adaptation of the operation of forced supply and exhaust ventilation in accordance with the concentration of carbon dioxide in the air in public, industrial and residential buildings, especially in isolated rooms (tunnels, underground garages, motor and test benches, etc.);
• triggering alarms in public and industrial buildings;
• reduction of power consumption by ventilation and air conditioning systems;
• exhaust air quality control at industrial enterprises for timely troubleshooting.

Introducing the range of CO2 sensors from FuehlerSysteme:

The CO2 diagnostic accuracy is 100 ppm (ppm). Three different threshold ranges can be set: 0 - 2000/5000/10000 ppm.

Devices are capable of operating at temperatures from -20 to +50 degrees Celsius. The operating range of relative humidity is from 0 to 98%, provided that the air is not condensed and does not contain a large percentage of chemicals.

Both two-wire and three-wire connections are available. The output signal is 0 - 10 volts or 4 - 20 milliamps. Manual zero point adjustment is provided. An automatic calibration is performed every seven days. Exit to the operating mode occurs only after self-diagnosis and start of the thermostat.

The type of sensor device is a non-diffuse infrared (NDIR) measuring element.

Types of carbon dioxide sensors FuehlerSysteme:

outdoor

ducted

Indoor

CO2 and temperature sensors

A line of carbon dioxide sensors has also been developed, an additional option of which is the ability to measure temperature in the range from 0 to +50°C. CO2 and temperature sensors are available in three configurations - duct, room, outdoor.

They allow you to start an alarm, ventilation, heating or thermostat in automatic mode in all types of rooms. The final signal can be given according to two criteria, which is relevant for industries where it is necessary not only to monitor the concentration of carbon dioxide, but also strictly observe the temperature regime.

The presented equipment complies with European standards: CE, EAC, RoHS.

Carbon dioxide sensors can improve people's quality of life and create comfortable working conditions by preventing harmful carbon dioxide concentrations from affecting the body. They are also indispensable in production, when exhaust air control is carried out. CO2 sensors can be integrated into the air conditioning system or connected to another type of thermostat if equipped with the optional temperature measurement option. This will allow more stringent control over production processes. In addition, carbon dioxide sensors can significantly reduce the cost of maintaining a forced ventilation system by reducing the amount of electricity it consumes. This makes this device an indispensable component in modern automated engineering communications systems.