What are the effects of increased CO2 concentrations, even indoors?
We are all familiar with the impact of CO2 emissions on global warming. Carbon dioxide accumulates in the atmosphere primarily due to the combustion of fossil fuels, contributing to climate change.
CO2 is a gas composed of one-third carbon and two-thirds oxygen. Plants use it in photosynthesis to produce carbohydrates, the fundamental energy source for living organisms. Since humans and animals depend on plants for sustenance, photosynthesis is essential for life.
Carbon dioxide is a colourless and odourless greenhouse gas that naturally occurs in small quantities and is generally harmless. However, elevated concentrations can negatively impact cognitive function and sleep quality. In poorly ventilated indoor spaces, CO2 accumulates due to human respiration.
Indoor CO2 levels tend to rise in spaces where people, machinery, and equipment operate in confined areas. Modern buildings, offices, and homes are increasingly designed to be energy-efficient and airtight. While this reduces energy consumption, it limits fresh air circulation, leading to higher CO2 concentrations and poorer indoor air quality.
Risks
Studies have established a direct link between elevated indoor CO2 levels, decreased productivity, and increased illness risk in homes, workplaces, and schools. High CO2 concentrations can cause headaches, fatigue, restlessness, and even elevated heart rate and blood pressure. Research indicates that as CO2 levels rise, cognitive tasks become more challenging.
Indoor CO2 levels fluctuate based on several factors, including ventilation efficiency, the number of occupants, and their stay in an enclosed space. Adequate ventilation is crucial for maintaining a healthy indoor environment. Ideally, doors and windows should be opened regularly to prevent the buildup of stale air. However, this is not always feasible, particularly during colder months, making ventilation systems essential.
For years, plants were believed to significantly reduce indoor CO2 levels. While they do play a role in global CO2 reduction through photosynthesis, an impractically large number of plants would be required to improve indoor air quality noticeably.
Much research has been reported on the effects of carbon dioxide (CO2) on the human brain. The impact of CO2 on human cognition and decision-making does not only affect workers in highly polluting industries. Evidence shows indoor CO2 negatively impacts school and university test scores and learning ability. It can have a generally adverse effect on productivity. Many researchers, therefore, point out that the impact of carbon dioxide on cognitive function and decision-making is proportional to the CO2 concentration in the air.
Significance of CO2 levels
250-400 ppm
Normal background concentration in outdoor air.
400-1,000 ppm
Typical concentrations for inhabited indoor spaces with good air exchange.
1,000-2,000 ppm
Complaints of drowsiness and poor air quality.
2,000-5,000 ppm
Headaches, drowsiness, stagnant, stale, stuffy air, lack of concentration, loss of alertness, increased heart rate and mild nausea.
40,000 ppm
Exposure can cause severe oxygen deficiency, leading to permanent brain damage, coma and even death.
Research on CO2 effects on human cognition indoors is still considered preliminary. However, it is assumed that human behaviour is impaired in CO2-enriched environments.
Studies have shown that indoor CO2 levels are much higher than outdoor levels. Many people spend much of the day in indoor spaces such as homes, schools, workplaces, shopping malls or institutions like hospitals. So they are exposed to CO2 levels above the 350-400 ppm range. The values can be up to 1500–2000 ppm or more, depending on the number of people present and the amount of ventilation in the respective rooms.
Many modern buildings today are designed to reduce energy consumption. Likewise, air conditioning systems are designed to provide a comfortable temperature. Unhealthy indoor air remains an issue. Energy consumption is mainly attributed to air conditioning systems. Ventilation with outside air is often switched off, and the same cooled air circulates. This is done to prevent ventilation from outside air from supplying either a higher or lower temperature. This is how modern offices work; children and students learn in air-conditioned classrooms. Little attention is paid to poor indoor air quality or to the fact that without ventilation, indoor spaces will gradually absorb increasing levels of CO2 over time.
Researchers at the University of Berkeley conducted a decision-making test in which they simulated the management of an organisation in a crisis. The subjects participated in three parts, each lasting two and a half hours, under identical conditions. However, the CO2 concentrations varied. An increase in CO2 concentration of 400 ppm could decrease complex strategic thinking.
A famous study by Professor Joseph Allen of the Harvard School of Public Health measured a fifteen percent lower cognitive performance value at 950 ppm and a further 50 percent decrease at 1400 ppm.
So, monitoring and measuring CO2 levels in homes and workplaces is crucial. Once problems are identified, solutions can be implemented. Ventilation plays a key role in reducing CO2 in indoor air. However, ventilation can also introduce a variety of other pollutants. Therefore, it is vital to find the right balance. Fresh air, with careful filtering if necessary, ensures a healthy, liveable indoor climate and general well-being.
Apart from the additional CO2 emissions from industry, for example, the CO2 emissions from people are also interesting. Every person releases CO2 naturally and breathes out an average of fifteen to twenty litres of air per hour when sitting. The carbon dioxide emissions of a single person per day add up to the amount produced by a small car driving ten kilometres.
Conclusion
Physiological basis
Improved brain function due to increased oxygen supply at CO2 levels below 430 ppm.
Activated oxygen transport in the blood.
More effective mitochondria.
Performance differences
At 400 ppm vs. 800 ppm: fifteen percent better cognitive performance.
Noticeable concentration problems from 800 ppm.
At 1000 ppm, a 30 % reduction in performance (creativity and complex thinking).
Economy in general
Better air quality increases productivity by three to seven percent.
Fewer sick days, higher innovation, better decision-making ability.
Underestimation of problems
Outdated limit values.
You can focus on the added value of energy savings instead of performance optimisation.
Lack of perception of subtle effects.
Measurement
Thresholds serve to minimise health risks, not to restrict cognition.
Invigorating economic effect of a reduction to 400 ppm.
Difficult to measure air quality and complex and challenging to prove improvement in productivity thanks to air quality.
Carbon dioxide concentration in the air is essential for indoor air quality.
Excessive CO2 concentrations can lead to tiredness, headaches and concentration difficulties.
Ways of enriching the room air with oxygen
Regular ventilation is simple and effective.
Open all the windows for a quarter of an hour several times daily.
Shock ventilation is more efficient than keeping the windows tilted open.
Plants as a minimal contribution
Houseplants produce oxygen and consume carbon dioxide. However, this is a minimal contribution to improving indoor air quality.
The most effective plants are the arrowhead plant and the peace lily.
Ventilation systems
Modern ventilation systems for automatically exchanging and filtering indoor air.
Such systems are particularly useful in well-sealed buildings or offices.
Oxygen concentrators
Oxygen concentrators filter and concentrate oxygen from the surrounding air.
These devices are primarily used in medical applications but also private households. Information from specialists is essential. Improper oxygen enrichment of the surrounding air can also pose a hazard.
Air purifiers with ionisers
Some air purifiers are equipped with ionisers that generate negative ions. These can help improve air quality by removing dust and other particles.
Tip
- Could you make sure of a balanced humidity level?
- Air that is too dry can also cause discomfort.
- Avoid smoking indoors.
- Carpets, curtains, and textiles should be cleaned regularly. This is generally recommended to minimise dust mites and allergens.