Although carbon dioxide gas is considered non-toxic, it can still have negative health effects at high concentrations. When indoors are crowded or poorly ventilated, carbon dioxide gas concentrations can continue to rise, leading to symptoms such as headaches, fatigue, and decreased concentration. Therefore, measuring indoor CO2 gas concentrations is an important means of ensuring air quality and living comfort.
Why monitor indoor CO2 gas?
The level of carbon dioxide outdoors is generally 410-420ppm, which is very safe. It is slightly higher in big cities, but generally does not exceed 450ppm. The concentration of carbon dioxide gas exhaled by humans is about 30,000ppm. Therefore, places with poor ventilation and small spaces are prone to high concentrations of carbon dioxide.
Let’s take a look at the comparison of human body reactions as indoor CO2 concentrations increase:
| CO2 level (ppm) | 350~450 | ＜1000 | 1000~2000 | 2000~5000 | ＞5000 |
| Effects on humans | No effect | No adverse effect | Easy to feel drowsy | Headache, fatigue, lack of concentration | Will cause permanent brain damage |
We have done a simple test. In a 20-square-meter single bedroom, with doors and windows closed, an adult in the room without any physical exercise, the carbon dioxide gas concentration can rise from 450ppm to more than 1000ppm in 2-3 hours. It will continue to rise for a while after falling asleep, reaching a maximum of 1600ppm. It may gradually stabilize or slightly decrease when the human body enters a deep sleep state. If two people talk in the bedroom, it can reach 1500ppm within 2 hours and continue to rise. The better the airtightness of the room, the higher the indoor carbon dioxide concentration will be. Cooking, human and pet breathing will cause the carbon dioxide concentration to rise rapidly. It is not uncommon to exceed 3000ppm, and it cannot be permanently solved by one-time ventilation.
One space worth mentioning is the car. When the car doors and windows and ventilation system are closed, a person breathing in the car may cause the carbon dioxide concentration to quickly exceed the dangerous concentration of 5000ppm, which is enough to cause brain damage.
What are the sources of indoor CO2?
Human activities are the main source of indoor carbon dioxide.
An adult can exhale about 22.6 liters of carbon dioxide per hour in a quiet state. When the amount of activity increases, the exhaled carbon dioxide gas will double. If there are many people in the room and the living is crowded, the carbon dioxide gas concentration will increase significantly.
The main gaseous metabolite in the human body is carbon dioxide, and carbon dioxide accounts for about 4% to 5% of the exhaled air. An adult can exhale about 22.6 liters of carbon dioxide per hour in a quiet state, and children are about 50% of adults. If there are many people in the room and the living is crowded, the carbon dioxide content will increase significantly.
The kitchen is also a place where the concentration of carbon dioxide is likely to exceed the standard.
Burning wood and gas also consumes oxygen and produces carbon dioxide. If ventilation is not carried out in time, the concentration of carbon dioxide will be too high. Organic matter in kitchen waste will release carbon dioxide during deterioration, decomposition, fermentation and decay.
Other sources
Smoking, indoor green plants and pet cats, dogs, birds, etc. can all emit carbon dioxide. Large amounts of stored vegetables can also produce a certain amount of carbon dioxide.
How to detect indoor CO2?
1. Handheld CO2 detector
Handheld CO2 detector is a more traditional method of indoor CO2 detection. It is very simple to use. Just turn it on and approach the detection point. The detector will immediately display the current CO2 concentration value. The advantages of handheld CO2 detector are portability, simple use, and low price. The disadvantage is that it needs to be close to the detection point during use, and some difficult-to-reach places cannot be detected. In addition, the handheld CO2 detector can only detect the CO2 concentration value within the current time and cannot be monitored for a long time.
2. Electrochemical CO2 sensor
The electrochemical CO2 sensor is a detection device that is directly installed indoors like an ordinary temperature and humidity sensor. The CO2 sensor can continuously monitor the indoor carbon dioxide level 24 hours a day and automatically upload the data to the management platform. The advantages are easy to use, no manual intervention, and the ability to monitor the indoor CO2 concentration for a long time. The disadvantage is that the price is relatively high, but with the continuous development of technology, the prices of some brands have begun to become reasonable.
3. Smart home devices
Modern smart home devices (such as smart air conditioners, air purifiers, etc.) often integrate CO2 sensors to automatically monitor air quality. When CO2 concentration exceeds the standard, these devices can automatically adjust ventilation or start air purification to optimize indoor air quality. It can effectively manage energy, reduce energy waste, and have a positive impact on indoor pollutants. The disadvantages are high price, complex installation, and easy leakage of user privacy.
How to reduce indoor CO2?
1. Enhance indoor ventilation
Ventilation is one of the simplest and most effective ways to reduce indoor carbon dioxide concentration. By opening windows, setting up mechanical ventilation systems or starting the fresh air function of air conditioners, fresh air from the outdoors can be introduced into the room to expel indoor carbon dioxide. Especially in confined spaces, enhanced ventilation can effectively reduce carbon dioxide concentrations.
2. Increase green plants
Green plants have a positive effect on improving indoor air quality. Because they can absorb carbon dioxide through photosynthesis and release oxygen. Placing some common indoor green plants, such as ivy, spider plants, aloe vera, etc., indoors can effectively reduce indoor carbon dioxide concentrations.
3. Use air purifiers
Indoor air purifiers can filter out pollutants in the air, including carbon dioxide. Using an indoor air purifier, you can effectively remove various indoor pollutants, including the content of natural gas dioxide, to ensure the health of residents.
4. Control the number of people
The carbon dioxide in indoor air mainly comes from the breathing of people. Therefore, controlling the density of people indoors can reduce the generation of carbon dioxide. For example, in a crowded indoor space, work or study can be divided into time periods to avoid crowding and reduce the generation of carbon dioxide.