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Basic Knowledge on Gases

Carbon Dioxide

Carbon Dioxide (Chemical formula: CO2
CO2 is colorless and odorless gas at normal room temperature. It is exhaled by humans and animals, and released in air by burning of fossil fuels and other organic substances. CO2 is consumed in photosynthesis in trees and green plants. CO2 is called carbon dioxide gas in a gas form, dry ice in a solid form, and aqueous solution of CO2 is called soda water or carbonated water. It is used in many fields for industrial applications.

■Effects of CO2 on Health

CO2 is widely used in fire extinguishers, as a refrigerant (dry ice), and in other applications. CO2 is not classified as toxic in general. However, caution is required in case of high concentration CO2 being present in air since there is a risk of carbon dioxide poisoning due to improper usage or handling of CO2.

Health Effects
400 Average outdoor air level
400 - 1,000 Typical level found in occupied spaces with good air echange.
1,000 - 2,000 Level associated with complaints of drowsiness and poor air.
2,000 - 5,000 Level associated with headaches, sleepiness, and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present.
5,000 This indicates unusual air conditions where high levels of other gases could also be present. Toxicity or oxygen deprivation could occur. This is the permissible exposure limit for daily workplace exposures.(*)
40,000 This level is immediately harmful due to oxygen deprivation.

* Based on the United States’ Occupational Safety and Health Administration guideline

■Impact on Global Warming

Global Greenhouse Gas Emissions by Gas (2010)

Source: The Fifth Assessment Report 2014 of the Intergovernmental Panel on Climate Change (IPCC). Figure drawn by Figaro Engineering Inc. based on global emissions in 2010

It is said that the Global warming is mainly attributed by an increase in greenhouse gases in the atmosphere. Greenhouse gases absorb and retain the heat from the surface of the earth in the atmosphere and return it to the Earth’s surface again (greenhouse effect). Since the Industrial Revolution in the mid of 18th century, the concentration of greenhouse gases in the atmosphere has increased sharply because of fossil fuel use and deforestation.
Among typical greenhouse gases such as CO2, methane, nitrous oxide, F-gases, etc., CO2 has the biggest impact on global warming. Its concentration level in the atmosphere has been increasing in recent years.

Reducing CO2 emissions is a major issue to mitigate global warming and for sustainable social environment and natural environment.

■Recent Trends in Japan

【CO2 level used as an indicator for ventilation】
The Ministry of Health, Labor, and Welfare of Japan recommends that indoor CO2 concentration should be kept below 1000ppm as a standard for good ventilation. To meet this standard, frequent ventilation is required in densely populated places such as houses, restaurants, or offices.

CO2 measuring instrument is recommended as an effective way to check whether the ventilation condition meets the requirement or not. From the perspective of measurement accuracy, it is recommended to use a CO2 measuring instrument with an NDIR type CO2 sensor integrated.

【Agriculture applications】
The environment inside a closed greenhouse is prone to insufficient CO2 for growth of vegetables. Since CO2 is essential for photosynthesis in plants, CO2 deficiency may cause poor vegetable growth consequently. By controlling the CO2 concentration in a greenhouse using a carbon dioxide generator, it is expected to improve quality, growth, and yield of crops or vegetables.