When it’s stuffy: stuffy room and hypercapnia. I continue experiments with CO2 in the apartment. Dangerous concentrations of CO2.

This information is intended for healthcare and pharmaceutical professionals. Patients should not use this information as medical advice or recommendations.

Basics of CO 2 monitoring

Practical guide(based on materials from Datex)
Novosibirsk 1995

1.Introduction 2

2.What is a capnogram. 3

3. How CO 2 is formed in exhaled air 4

4.Why is PetCO measured 2 6

5.Diagnostics of hyper- and hypoventilation 7

6. Interpretation of capnogram and trend of CO 2 9

7. Practical guide to CO2 monitoring 15

8.CO2 monitoring in the post-anesthesia period 16

Appendix 18

The practical guide was compiled based on materials from the Datex company by the research and production company LASPEC JSC

Translation and computer layout - D.E. Groshev
Editor Ph.D. - O.V. Grishin.

1. Introduction.

These guidelines are designed for anesthesiologists and resuscitators who are not familiar with CO 2 monitoring, and aim to answer in a simple form the question: “why and how is CO 2 monitoring performed?” Mastering several basic principles of CO 2 monitoring provides the doctor with rich information about the condition patient and the functioning of anesthesia equipment. A list of literature recommended for more detailed study is given in the “Reference Literature” section.

Carrying out CO 2 monitoring in anesthesiology and resuscitation is considered very important and even a necessary condition effective monitoring of patients with controlled or impaired breathing, as well as with normal breathing if there is a threat of its disruption. The rapid growth in popularity of CO 2 monitoring reflects its importance in ensuring patient safety. With its help, many potentially dangerous situations are detected at the earliest stages of development, providing the doctor with sufficient time to analyze and correct the developing critical condition. In addition, monitoring the end-tidal CO 2 concentration (PetCO 2) and analyzing its trend provide the most objective diagnostic information about the patient’s condition during anesthesia.

The table provides an assessment of the relative importance of a number of techniques for identifying critical situations. (Whitzer C. et al. Anasthetic mishaps and the cost of monitoring: a proposed standard for monitoring equipment. J. Clin Monit 1988; 4:5-15p.).

2.What is a capnogram.

The curve of changes in CO 2 concentration over time is called a capnogram. It reflects the different stages of exhalation. The capnogram is an important diagnostic tool, since its shape is almost the same in healthy people. Therefore, any change in the shape of the capnogram should be analyzed.

*Dead space called the part of the airways where gas exchange does not occur. In the case of hardware monitoring of CO 2, they take part in the formation of the exhalation capnogram: following types dead space. Mechanical or hardware dead space - consists of an endotracheal tube and connecting hoses. Anatomical dead space - consists of the trachea and bronchi. Alveolar dead space - makes up the part of the respiratory tract in which gas exchange does not occur, although it is ventilated.

What is PetCO 2?

The maximum concentration of CO 2 at the end of tidal expiration PetCO 2 (end-tidal CO 2) is very closely related to the alveolar concentration of CO 2, since it is recorded during the flow of air from the alveoli.

3. How CO 2 is formed in exhaled air.

A comparative analysis of arterial blood and alveolar air shows that the PetCO 2 value quite closely tracks the level of CO 2 tension in the blood (PaCO 2), but they are still not equal. Normally PetCO 2 is 1-3 mmHg. lower than PaCO 2. However, in patients with pulmonary pathology, the differences can be significantly greater. The reasons for this are complex, and identifying an increase in this difference gives us an additional diagnostic parameter: the arterial-alveolar difference (aADCO 2). In fact, aADCO 2 can be considered as a quantitative indicator of alveolar dead space, so significant changes in it should be further investigated.

Small arterial-alveolar difference.

The arterial-alveolar difference is the result of the characteristics of the processes of ventilation and perfusion of the pulmonary alveoli. Even in a healthy patient, ventilation-perfusion ratios differ in different parts of the lungs. During anesthesia, the ventilation-perfusion mismatch usually increases slightly, but this is usually not clinically significant.

The main reasons for the increase in aADSO 2.

A decrease in the level of gas exchange occurs in that part of the respiratory parts of the lungs that do not have sufficient perfusion, but are nevertheless well ventilated. When you exhale, air from these areas of the lungs will mix with CO 2 -rich alveolar air from the rest of the lungs, reducing PetCO 2 . In this case, aADCO 2 will be increased. This type of ventilation is called alveolar dead space ventilation.

Possible reasons causing an increase in aASO 2 are:

patient position (side position)

pulmonary hypoperfusion

pulmonary thromboembolism.

Drawing A illustrates the effect of alveolar dead space ventilation. Half of the lungs have no perfusion and therefore no gas exchange. When you exhale, the alveolar gas mixes and the resulting concentration of PetCO 2 will be half that of PaCO 2 in the blood. For comparison, figure IN illustrates the ideal situation when perfusion occurs throughout the entire volume of the lungs and PetCO 2 =PACO 2 =PaCO 2 .

4. Why is PetCO 2 measured?

CO 2 monitoring provides information both on the patient’s condition and on the ventilation system. Since CO 2 concentration depends on many factors, it is rarely sufficient to make a specific diagnosis. However, CO 2 monitoring with a quick indication and display of the CO 2 concentration in each exhalation provides sufficient time to take the necessary corrective measures.

Clinical benefits of CO 2 monitoring.

Under conditions of a stable patient condition (ventilation combined with normal hemodynamics), the CO 2 concentration is closely related to the change in CO 2 tension in the blood and, therefore, is a non-invasive method for monitoring PaCO 2. The release of CO 2 is a fairly stable value, so sudden changes in PetCO 2 usually reflect either changes in blood circulation in the pulmonary circulation (for example, pulmonary embolism) or pulmonary ventilation (for example, tube disconnection or excessive ventilation - hyperventilation).

• Quickly determine the correctness of tracheal intubation.

Quickly identify abnormalities in the air tract (endotracheal tube connector, endotracheal tube, airway) or in the air supply system (ventilator).

Objectively, continuously, non-invasively monitor the adequacy of ventilation.

Recognize disorders in gas exchange, pulmonary circulation and metabolism.

Provides control safe use low-flow anesthesia techniques with their inherent economical consumption of inhalational anesthetics.

Reduces the need for frequent routine blood gas testing because the PetCO 2 trend mirrors the PaCO 2 trend. Blood gas analysis becomes necessary in cases of significant deviation of the PetCO 2 trend.

Common terms for CO 2 monitoring

“kapno” means the level of CO 2 when exhaling (from the Greek “kapnos” to smoke); “hyper” means too much; “hypo” means too little.

Using PetCO 2 to control ventilation.

Normally, during quiet natural breathing, the gas exchange function of the lungs provides a partial pressure of CO 2 in the blood (PaCO 2) of about 40 mm Hg. This happens by regulating the frequency and depth of breathing. With an increase in CO 2 release (for example, during physical activity), the frequency and depth of breathing increases proportionally. During anesthesia with muscle relaxants, the anesthesiologist must ensure adequate levels of ventilation. Typically this level is estimated by calculating the required ventilation using nomograms. Much more effective method control of adequate ventilation is based on CO 2 monitoring.

Physiological factors controlling CO 2 removal.

Removal of CO 2 depends on 3 factors: metabolic rate, the state of the pulmonary circulatory system and the state of the alveolar ventilation system.

It must be remembered that these 3 factors are interconnected. Changes in the acid-base balance (or state of the CBS), caused by various reasons, can also affect the removal of CO 2.

Experience in diagnosing various critical situations during mechanical ventilation comes quite quickly. Thus, if the steady-state value of CO 2 increases with constant ventilation, changes in PetCO 2 usually arise from changes in the pulmonary circulation. In this case, you should pay attention to changes in metabolism or CBS.

During anesthesia, the metabolic rate usually changes little (the main exception is the rare case of malignant hyperthermia, which causes a sharp increase PetCO 2.)

What is alveolar ventilation.

When the ventilation level is established, maintaining a stable and within the normal PetCO 2 limits, then there is no need to carry out any calculations. However, in order to be prepared for any situation, it is useful to know the features of pulmonary ventilation. As already mentioned, part of the air during breathing does not reach the alveoli and remains in the mechanical (connector, valve box, endotracheal tube) and anatomical (trachea, bronchial tree) dead space, where gas exchange does not occur. To calculate the volume of alveolar ventilation in l/min, which actually provides gas exchange in the lungs, it is necessary to subtract the volume of total dead space from the tidal volume. By multiplying the volume of air entering the alveolar spaces by the respiratory rate, one can obtain alveolar minute ventilation - an indicator of effective ventilation.

5. Diagnosis of hyper- and hypoventilation.

After the initiation of anesthesia and tracheal intubation, anesthesia is usually maintained by an artificial ventilation system in a steady state of CO 2 release. Note that during a long operation (more than 1.5 hours), due to the inhibitory effect of anesthetics and developing hypothermia, the patient’s metabolism slightly decreases and a gradual decrease in PetCO 2 is observed

Normocapnia and normoventilation.

Alveolar ventilation is usually set to ensure normocapnia - that is, PetCO 2 should be in the range of 4.8 - 5.7% (36 -43 mmHg). This type of ventilation is called normal ventilation, since it is typical for healthy people. Sometimes alveolar ventilation during mechanical ventilation is established with mild hyperventilation (PetCO 2 4-5%, 30-38 mm Hg).

Advantages of normoventilation.

When maintaining normal ventilation, the development of critical situations is much easier to recognize: disturbances of alveolar ventilation, blood circulation or metabolism. Spontaneous breathing is restored more easily. In addition, recovery in the post-anesthesia period is much faster.

Hypocapnia and hyperventilation.

A PetCO 2 level below 4.5% (34 mmHg) is called hypocapnia. Under anesthesia most a frequent occurrence hypocapnia is too high alveolar ventilation (hyperventilation).

In the post-anesthesia period, hypocapnia during spontaneous breathing of the patient may be the result of hyperventilation caused by fear, pain or developing shock.

Disadvantages of prolonged hyperventilation.

Unfortunately, hyperventilation of the patient is still a common practice during mechanical ventilation, which, according to generally accepted opinion, is necessary to ensure adequate oxygenation and even to deepen anesthesia. However, modern medicines and monitoring techniques can provide better oxygenation and anesthesia without hyperventilation “just in case.”

Hyperventilation has quite serious disadvantages:

vasoconstriction, leading to decreased coronary and cerebral blood flow;

excessive respiratory alkalosis;

depression of the respiratory centers;

All these factors lead to a more difficult and prolonged recovery in the post-anesthesia period.

Hypercapnia and hypoventilation.

Exceeding the PetCO 2 level of 6.0% (45 mm Hg at Ratm = 760) is called hypercapnia. The most common cause of hypercapnia during anesthesia is insufficiency of alveolar ventilation (hypoventilation), caused by a low level of tidal volume and (or) respiratory rate. In addition, in a closed ventilator circuit, prolonged hypercapnia can be caused by insufficiently complete absorption of CO 2. On the capnogram, this is manifested in the fact that the CO 2 concentration in the inhalation phase does not fall to zero.

In the post-anesthesia period, prolonged hypercapnia during spontaneous breathing of the patient can be caused by:

residual neuromuscular block;

drug suppression of respiratory centers;

painful restriction of breathing (especially after surgery on the abdominal organs).

Note that hypercapnia can be accompanied by hypoxia, but this is not necessary. The hypoxic state occurs later than hypercapnia with more low values alveolar ventilation.

Additional clinical manifestations of hypercapnia are: tachycardia, the appearance of perspiration, increased tension, headache, anxiety. With prolonged hypercapnia, undesirable side effects occur, such as a tendency to cardiac arrhythmias (with exposure to volatile anesthetics), increased cardiac output, increased intracranial pressure, pulmonary vasoconstriction and peripheral vasodilation.

6. Interpretation of capnogram and CO 2 trend.

CO 2 monitors typically display a real-time CO 2 trace of each exhalation (capnogram) and a 30-minute PetCO 2 trend. Abrupt changes in CO 2 emissions are clearly visible on an exhalation capnogram, while gradual changes are better visible on the CO 2 trend.

Normal capnogram.

Capnogram healthy person with artificial ventilation it has a normal shape. Any significant deviation from the normal capnogram shape reflects a disturbance in the respiratory system, complex or mechanical disturbances in the ventilator circuit.

CO 2 suddenly ceased to be detected.

If the capnogram had a normal appearance, and then abruptly stopped to zero, during one exhalation, the most likely cause is a violation of the tightness of the ventilation circuit.

Another possible reason is complete obstruction of the respiratory tract, for example caused by kinking (kinking) of the endotracheal tube.

Exponential Decline PetCO 2.

A rapid drop in PetCO 2 over several breaths may indicate:

• severe pulmonary embolism
• cardiac arrest
• significant drop in blood pressure (severe blood loss)
• severe hyperventilation (due to mechanical ventilation).

Stepwise drop in PetCO 2 level

Moving the endotracheal tube into one of the main bronchi (for example, when the patient's position changes).

• Sudden partial airway obstruction.

Gradual reduction of PetCO 2.

Gradual increase PetCO 2

A gradual increase in PetCO 2 over several minutes can be caused by the onset of hypoventilation, an increase in metabolic rate as a result of the patient’s reaction to stress (pain, fear, injury, etc.).

Esophageal intubation.

Malignant hyperthermia.

The CO 2 monitor is a fast-acting indicator of malignant hyperthermia. A rapid increase in metabolic rate is easily detected by the increase in PetCO 2 (inspiratory CO 2 remains zero).

Incomplete muscle relaxation.

With incomplete muscle relaxation and insufficient depth of anesthesia, the patient retains his own breathing, “working” against mechanical ventilation. This shallow spontaneous breathing causes dips in the capnogram.

Partial airway obstruction.

A distorted capnogram (slow rise rate) may indicate partial airway obstruction. Possible causes of obstruction may be:

generalized bronchospasm,

mucus in the respiratory tract,

kinking of the endotracheal tube.

Rebreathing effect.

An increase in the inhalation CO 2 concentration reflects the effect of recurrent breathing, which consists in the fact that the patient inhales CO 2 exhaled by him into a closed ventilator circuit (incomplete absorption of CO 2 in the ventilator circuit).

Capnogram oscillations during cardiac contractions.

With weak breathing (especially in the second half of exhalation with extreme low speeds flow) heart contractions may appear in the falling portion of the capnogram. Capnogram oscillations occur due to the movement of the heart against the diaphragm, causing an intermittent flow of air towards the endotracheal tube.

Restoring natural breathing.

In a critical situation, the patient is usually manually ventilated with 100% oxygen. At the same time, PetCO 2 is deliberately allowed to grow in order to trigger spontaneous respiration. After which the patient with unimpaired ventilation quickly achieves satisfactory alveolar ventilation.

Children's capnogram.

The figure shows a typical capnogram obtained using the Jakson-Rees breathing system in pediatric anesthesia. The initial rebreathing was caused by insufficient purification of the gas flow, which was subsequently corrected. A distinct alveolar plateau confirms that the “real” PetCO2 value is being recorded.

Heart failure.

A rapid decline in the height of the capnogram, while maintaining the correct shape, shows a sharp drop in pulmonary perfusion due to weak cardiac output (1). During cardiac asystole, CO 2 is not transported to the alveoli by the pulmonary bloodstream (2). Effective cardiopulmonary resuscitation begins (3). The restoration of blood flow is confirmed by an increase in the capnogram.

CO 2 trend and real-time capnogram will help you evaluate the entire procedure and its effectiveness.

7. Practical guide to CO 2 monitoring.

CO 2 monitors use small amounts of gas to measure, which are continuously withdrawn from the patient's air tract (150 - 200 ml/min). The side gas monitor can be used with all types of anesthesia circuits. A nasal adapter is used to monitor CO2 during natural breathing.

The basic rule for placing a gas sampler.

Place the gas sampling adapter as close to the patient's mouth or nose as possible. This way, you eliminate unwanted “dead space” between the gas sampling site and the patient, and the measured PetCO 2 concentration will more accurately correspond to the alveolar CO 2 level.

When a heater and moisture exchanger are used to heat and humidify inspired air, the gas sampling adapter should be located between the endotracheal tube and the heater and moisture exchanger.

In particular, when closed circuit ventilation is used, the gas sampling adapter should be located near the endotracheal tube to prevent mixing of purified and expired gases.

Connecting tubes should not be cleaned after use. Cleaning with chemicals can damage the inside of the tubes and increase resistance to gas flow.

Steel gas sampling adapters are reusable and can be sterilized, but plastic adapters are intended for single patient use only.

Use only original tubes and adapters. Using other samples may result in incorrect measurements.

Air tubes and adapters must be visually inspected prior to use.

Removing gas from the monitor output.

Gas comes out of the outlet fitting of the device with sufficient pressure. To prevent contamination of the room air with anesthetic gases, the monitor outlet tube must be connected to an exhaust ventilation hose.

Monitoring at low air flows.

Small volumes of gas that are sampled for monitoring are usually removed. However, if in closed system ultra-low flows are used, the gas after analysis must be returned to the exhalation branch of the breathing circuit.

8. CO 2 monitoring in the post-anesthesia period.

Using a nasal CO 2 gas sampling adapter, the monitor allows continuous measurement of PetCO 2 in a spontaneously breathing patient. At the same time, CO 2 monitoring is an excellent method for identifying apnea or depression of the respiratory centers.

If the patient remains under artificial ventilation The CO 2 monitor allows you to assess the patient's required level of ventilation continuously and non-invasively.

Often, a violation of the ventilation-perfusion relationship caused by pulmonary pathology manifests itself in the arterial-alveolar difference (aADSO 2). Measuring the concentration of CO 2 in arterial blood and comparing it with PetCO 2 provides an assessment of lung health. The reasons for changes in aADSO 2 must be clarified.

Nunn JF. Applied Respiratory Physiology, 2nd edition London: Butterworth, 1977.

Smalhout B, Kalenda Z. An Atlas of Capnography, 2nd edition. The Netherlands: Kerckedosh-Zeist,1981

Kalenda Z. Mastering Ifrared Capnography. The Netherlands: Kerckebosh-Zeist,1989

Paloheimo M, Valli M, Ahjopalo H. A Guide to CO2 Monitoring. Helsinki,Finland: Datex Instrumentarium Corp,1983

Lindoff B, Brauer K. Klinick Gasanalys. Lund, Sweden: KF-Sigma, 1988

Lillie PE, Roberts JG. Garbon Dioxide Monitoring. Anaesth Intens Care 1988;16:41-44

Salem MR. Hypercapnia, Hypocapnia and Hypoxemia. Seminars in Anesthesia 1987;3:202-15

Swedlow DB. Capnometry and Capnograpny: The Anesthesia Disaster Early Warning System. Seminars in Anesthesia 1986;3:194-205

Ward S.A. The Capnogram: Scope and Limitations. Seminars in Anesthesia 1987;3:216-228

Gravenstein N, Lampotang S, Beneken JEM. Factors influencing capnography in the Bain circuit. J Clin Monit 1985;1:6-10

Badgwell JM et al. Fresh Gas Formulae does not accurately predict End-Tidal PCO2 in Pediatric Patients. Can J Anaesth 1988;35:6/581-6

Lenz G, Kloss TH, Schorer R. Grundlagen und anwendungen der Kapnometrie. Anasthesie und Intensivmedizin 4/1985; vol 26: 133-141

Annex 1

“HARVARD STANDARD” for minimal anesthetic monitoring (1985).

The presence of an anesthesiologist is mandatory during the entire period of general and regional anesthesia.

Blood pressure and pulse rate (every 5 minutes).

Electrocardiography.

Continuous monitoring/ventilation and hemodynamics/.

for ventilation: monitoring the size of the breathing bag, auscultation of respiratory sounds, monitoring of inhaled and exhaled gases (PetCO2).

for blood circulation: palpation of the pulse, auscultation of heart sounds, observation of the blood pressure curve, pulse plethysmography or oximetry.

Monitoring of depressurization of the breathing circuit with an audible signal.

Oxygen analyzer with a preset alarm level for the minimum oxygen concentration.

Temperature measurement.

However, not everyone knows that at this moment there is less and less oxygen in the room. This is because most air conditioning systems can only cool the air that we have breathed for several hours, or maybe even days. The same thing happens in the car.

Symptoms to watch out for:

In the summer everything is fine, but in the winter there is complete apathy. We like to call it seasonal depression.
- in the morning everything is fine, but by the evening the brain refuses to work. Just like a zombie flipping through the Internet. You come home with wild fatigue and plop down on the sofa.
- woke up in the morning without an alarm clock and didn’t get enough sleep
- coffee green tea - do not give the expected effect, you become even angrier.
- you sleep as much as you want, but the dream is still not remembered.
- sometimes you can’t keep something important in your thoughts, it gets forgotten.
- we get up in the morning with extreme fatigue
- It seems that the room is dark.

And if you have similar symptoms at your workplace, then you have poisoning. What kind of poisoning is this? Carbon dioxide poisoning (not to be confused with carbon dioxide!). Carbon dioxide is not so harmless. The processes associated with an increase in its concentration are similar to poisoning. When the acidity of the blood changes, processes in the body proceed intermittently.

Lack of oxygen has an extremely negative effect on human body. We begin to feel tired and lethargic, the desire to do anything physically disappears, and our head completely refuses to work. Attributing the sluggish state to the heat, we continue to sit in a stuffy office or apartment, not suspecting what the true reason for the loss of strength lies.

The main factors that worsen air quality include the following:

• Temperature;


• Various smells;


• Level of gases in the atmosphere.

It is known that the last factor is the most important. Therefore, monitoring the CO2 level indoors is the primary task of every person. The CO2 content in indoor air is determined as follows:

• fresh air intake of 15 cfm = 25.5 m3/hour per person in the room corresponds to a CO2 concentration level of 1000 ppm


• fresh air intake of 20 cfm = 34 m3/hour per person in the room corresponds to a CO2 concentration level of 800 ppm

So, in order not to become a sleepy fly, a person needs a special alarm clock.

What should I do?

With a CO2 analyzer you will forever forget about the problem of oxygen starvation. Usually you work and forget about everything. And this compact companion will remind you every time you need to ventilate the room.

There are three indicators of different colors on the device panel:

Green - there is enough oxygen in the air;
Yellow - there is an increased amount of carbon dioxide in the air (it is advisable to ventilate the room);
Red - the air is oversaturated with carbon dioxide (urgently open the window).

In addition to light sensors, the device is equipped with an audible alarm that sounds every time the indicator switches from one color to another.

Squeaks. Looks like we urgently need to open the window.

The temperature in the room in the morning was pleasant, but I felt something was wrong. The sensor showed 2380 ppm

I opened the window. 10 minutes of ventilation. I close it and measure it.

Carbon dioxide concentration dropped to normal 445 ppm

And temperatures up to 17 degrees Celsius

There are two buttons behind the device. To calibrate and configure the device. The instructions contain a detailed description.

There is an output for microUSB on the side. Can be connected to a computer. Using the ZG VIEW program, you can monitor the state of oxygen and temperature in the room.

When turned on, the device warms up for a few seconds.

And he freezes. Hooray! The room is fresh.

And then it became interesting to me. Is it harmful for the driver to drive? for a long time with the stove in recirculation mode? After all, oxygen also leaves and all this can lead to sad consequences. Moreover, many travel this way for a long time.

My recirculation button looks like a “circular arrow”

Freeze at the beginning.

We wait 10 minutes.

We wait 25 minutes. The temperature in the cabin is 30 degrees Celsius. I'm already ready to sleep. The windows were a little foggy.

Wow! The maximum reading of the device Hi (High) is 3000 ppm. I'm already gape and I urgently need to ventilate the interior.

Turn off recirculation. Half an hour passed. One person raised the CO2 concentration to undesirable and, one might say, dangerous. The person feels tired, drowsy and cannot concentrate on driving. As a result, it can lead to an accident. Therefore, it is recommended to turn on this internal recirculation mode for a short time - only if you urgently need to warm up or, conversely, cool the interior in a short time using an air conditioner. It is also used on dusty or heavily polluted road areas.

Fresh and good.

In public places

Now let's test the device in the field. Let's go to the Russian post, public transport and shopping center.

At Russian Post, after 5 minutes of standing in line, an uncomfortable feeling arose. CO2 concentration is above average. For comparison, you can see how much the device shows on the street.

The difference is 4 times.

I was traveling alone in a minibus, the performance was average. The driver did not open the windows and the ventilation was turned off. The interior heating was working on recirculation.

In an electric train, during off-peak hours the performance is the same as at a post office. The carriage is half full. It's scary to think about something going on during rush hour.

_____________________________________
The device is provided for testing

Carbon dioxide sensors are part of a building automation system and usually control forced ventilation and air conditioning. Power setting supply and exhaust ventilation Previously, it had to be carried out in accordance with established standards, which were focused on 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 operating forced ventilation system. Indeed, during the required volume of supplied and removed air may be much less than the calculated values. At the same time, the adaptive ventilation system, equipped with CO2 sensors, promptly performs air exchange in the room when required, creating comfortable and safe conditions for living and working.

Why is carbon dioxide dangerous for humans?

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

Increased concentrations of CO2 negatively affect 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, rather than sleep duration, will be more important for healthy sleep. Prolonged inhalation of air with a high carbon dioxide content leads to a deterioration of the immune system, 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.);
• launch alarm in public and industrial buildings;
• reduction of power consumption by ventilation and air conditioning systems;
• monitoring the quality of exhaust air at industrial enterprises for timely troubleshooting.

We present to your attention the line of CO2 sensors from FuehlerSysteme:

The CO2 concentration diagnostic accuracy is 100 ppm. Three different threshold ranges can be configured: 0 – 2000/5000/10000 ppm.

The 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.

There is the possibility of both two-wire and three-wire connection. The output signal is 0 - 10 volts or 4 - 20 milliamps. Manual zero point adjustment is provided. Automatic calibration is performed every seven days. Entry into operating mode occurs only after self-diagnosis and startup of the thermostat.

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

Types of FuehlerSysteme carbon dioxide sensors:

External

Duct

Indoor

CO2 and temperature sensors

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

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

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

Carbon dioxide sensors have the potential to improve people's quality of life and create comfortable conditions labor, preventing the influence harmful concentrations carbon dioxide on the body. They are also indispensable in production when monitoring exhaust air. CO2 sensors can be integrated into the air conditioning system or connected to another type of thermostat if equipped with an additional temperature measurement option. This will allow for stricter control over production processes. In addition, carbon dioxide sensors can significantly reduce maintenance costs compulsory system ventilation, reducing the amount of electricity it consumes. This makes this device an indispensable component in modern automated systems engineering communications.

To analyze the situation in other rooms

As it turned out, even if you leave the module in a room without a door and with a closed window, as is actually happening in my kitchen in the near future

The presence of carbon dioxide will be normal only if there is no one there.

The picture shows a simple example:
1 - the wife had been cooking in the kitchen up to this point and left
2 is the amount of CO2 after 2 hours have passed and no one entered the kitchen, and the window was opened accordingly to ventilate
3 - I came home from work and sat and worked in the kitchen until 2 am, the arrow shows the moment when I went to bed. The graph shows that after I left without an open window, the CO2 concentration could not drop to normal even after 6 hours!
4 - the wife woke up, went into the kitchen, quickly had a snack and ran off to work
5 - I woke up and occupied the kitchen
6 - there is a huge amount of CO2 in the kitchen due to the worker who makes the floors in the hallway.....

This analysis gives grounds to assert that even one person can easily inhale even in a room without a door. You say, “What’s the problem with ventilating?”, the answer is simple - yes, it’s that you need to ventilate like this every 1-2 hours, it’s very convenient, right? Especially when you're sleeping)

For example, here’s how Tion copes with a large concentration of CO2, this is our bedroom and my wife and I went to bed at the same time at point 1 and, accordingly, we both immediately inhaled more than 1000 ppm, the device immediately recorded this and began to evenly blow in fresh air from the street so that the value dropped to 750ppm

Thus, by placing these sensors in rooms, you can control the CO2 concentration throughout the apartment. By the way, analyzing the statistics turned out to be extremely exciting, so what do you think was the spike in the top graph? The answer is simple - my wife was ironing in the room)))

By the way, it is important not to confuse the module and the base station, visually this is of course simple because they are the same

But the functionality is different:

This way you can save 2000 rubles and buy only a module for the second Breezer, or use it, as in my case, purely as a sensor that analyzes the situation in the room)

In general, I come to the conclusion that now I want something like this not only in the bedroom, but also in big room- an unrealistically cool thing) For skeptics, I’ll tell you right away - the electricity consumption per year of one such device is a ridiculous 394 kWh (thanks victorborisov for information obtained experimentally!)

Most of us spend a considerable part of our time at work in offices, in workshops with a soldering iron, and other enclosed spaces where there is often no natural ventilation. Especially the situation with the supply of fresh air from outside has worsened in recent years with the widespread arrival of plastic windows that practically do not breathe. In rooms where people are, there is always some part of 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. Outside the city and in rural areas The carbon dioxide concentration is usually 350 ppm, in the city 400 ppm, in the city center 450 ppm. The numbers vary greatly and depend on traffic density, wind strength and other factors. For example, in Moscow, on busy highways, the CO 2 level can reach 800-900 ppm.

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

There are several methods for measuring carbon dioxide concentration. The NDIR method of non-dispersive infrared spectrometry has become widespread in portable devices. 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 microns is used.

Until recently, CO 2 measuring instruments were too expensive for household use. Worldwide manufacturers of household CO meters 2 can be counted on one hand. But nevertheless, they exist and are already being sold with all their might 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 long ago, an inexpensive “Carbon Dioxide Detector” solution from the MasterKit company, widely known in amateur radio circles, appeared on the domestic market. This material is devoted to a short review of this meter. As with all products from MasterKit, of this meter There is a unique code - MT8057.

Device characteristics:

The detector is packaged in the following box:

The reverse side provides information about carbon dioxide and indoor levels.

The country of manufacture of the device is China. Looking ahead, I’ll let you know that I Googled two devices that are almost completely identical in appearance to the one being reviewed:
- ZGm053U
- CO2mini RAD-0301

The cost of the first is not indicated on the website, and the second device costs $100 excluding delivery costs. I paid 3,400 rubles for the device from MasterKit. together with delivery (data as of the end of January 2015). Today, I think it is unlikely to find a similar device anywhere at a lower or similar price.

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

Removing the meter:

On front side meter we see a screen for displaying CO 2 level and temperature, as well as three LED indicator: 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 to quickly assess the level of CO 2 concentration. After using the device for a week, I noted to myself that first of all I pay attention to these indicators, and not to the numbers on the device screen. In the device settings, you can set CO 2 levels for each LED.

Also this a good option for constructing DIY devices, for example, for controlling supply ventilation, household ventilators and other climate control equipment. You can solder to the LEDs or use photoresistors (or photodiodes) by placing them opposite the meter's LEDs. By adjusting the LED light levels, you can turn on or off supply ventilation upon reaching a certain threshold. This can be significantly 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 was expecting a device bigger size. 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 readable quite clearly. CO 2 and temperature readings:

The device is powered by a 5 Volt USB bus. Cable - microUSB. There is some recess on the device body for the USB connector, which is why not every micro-USB cable can be connected. In any case, of the 3 cables I have, not one went in all the way. Therefore, you need to be careful with the original cable and not lose it, otherwise you will then have to think about how to connect it to a regular normal cable.

It is not powered by batteries, which made me a little sad. For offline use you will have to use Power Bank with USB output.

By unscrewing the back cover we gain access to the insides of the device.

The long element with the sticker “ZGm053UK” is the heart of the device - an NDIR carbon dioxide concentration sensor. In the video below you can see how the lamp flashes for measurements. The flash rate is approximately 1 flash every 5 seconds.

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

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

The build and soldering quality is quite good.

A natural question may arise about the duration of the sensor operation. You can find the answer from the manufacturer ZyAura 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 sensor's lifetime is 5-10 years. The sensor needs to be calibrated approximately every three years.

There is special software for meters to display graphs and perform 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 unclear, especially considering that everything is in the archive.

The yellow line in the above graph is temperature (scale on the right). Bottom line - CO 2 level.
The room is approximately 12 sq.m. 1 person. Plastic windows. At about 2:35 p.m. the window was open. As can be seen from the graph, the temperature began to fall and, following it, the CO2 level immediately began to decrease to an acceptable value, after 10 minutes completely moving into the safe zone (in green on the graph). At about 14-50 the window was closed and the temperature and CO 2 began to gradually increase.

For Linux operating systems there is also OpenSource software posted on GitHub. Unfortunately, I was unable to compile the application under Debian OS, because... constantly complained about the package being missing, even though it was installed. But theoretically, this makes it possible to connect the meter via a USB interface to various Linux microcomputers (Raspberry Pi, CubeBoard, BeagleBone) and control devices (via GPIO) or upload data to some server, use it for a Smart Home system, etc. .P. There are already a lot of possibilities opening up here.

Whether a CO 2 meter is needed or not - everyone will decide for themselves; personally, I don’t regret the money spent on it and I’m even thinking about buying a second one, one for my 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 rather than a chemical one
• Long time interval for calibration
• Connection to a computer via USB for plotting
• Availability OpenSource software for Linux systems

Cons of MT8057:

• Lack of built-in power supply
• Abnormal recess in the case for a Micro-USB connector
• Low accuracy 100ppm, but quite sufficient for home use
• I would also like the presence of a humidity sensor