Our carbon dioxide (CO2) levels chart shows the increasing danger of elevated levels of CO2 in enclosed spaces.
Even a small increase of CO2 in the air by volume can be hazardous. While most people will never encounter CO2 levels above 1% indoors, the increased use of pressurized CO2 storage tanks in businesses has increased the likelihood of exposure to high levels of CO2. At 1% CO2, people can start to experience accelerated heart rate. 4% CO2 levels can be fatal.
What is an acceptable CO2 level in a room?
Normal CO2 levels in fresh air is approximately 400 ppm (part per million) or 0.04% CO2 in air by volume. The table below shows the effects of increased CO2 levels in an enclosed space.
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400 ppm 0.04% |
Normal outdoor air |
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400-1,000 ppm 0.04-0.1% |
Typical CO2 levels found indoors |
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1,000-2,000 ppm 0.1-0.2% |
Common complaints of drowsiness or poor air quality |
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2,000-5,000 ppm 0.2-0.5% |
Headaches, fatigue, stagnant, stuffiness, poor concentration, loss of focus, increased heart rate, nausea |
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> 50,000 ppm > 5% |
Toxicity due to oxygen deprivation occurs |
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> 100,000 ppm > 10% |
Oxygen deprivation in seconds: convulsions, coma, and death |
The acceptable level of carbon dioxide (CO2) indoors can vary depending on factors such as the purpose of the space, the number of occupants, and ventilation systems.
Generally, indoor CO2 levels are measured in parts per million (ppm). The following are some common guidelines:
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General indoor environments: In indoor settings, a CO2 concentration of 400-1,000 ppm is considered acceptable. This range is commonly used as a guideline for maintaining good indoor air quality in homes, offices, and public spaces.
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Offices and classrooms: In office spaces and classrooms, a common guideline is to maintain CO2 levels below 800-1,000 ppm. This is because higher CO2 levels have been found to lead to decreased cognitive performance and reduced productivity.
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Workplace environments: Workplaces covered by ASHRAE or OSHA guidelines mandate the permissible CO2 limit over a 15 minute time limit or an 8 hour workday. In addition, ASHRAE recommends that indoor CO2 levels be no more than 700 ppm above outdoor air levels.
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Building codes and standards: Different countries and regions have specific building codes and standards that dictate acceptable indoor CO2 levels. It's essential to check the local regulations for compliance.
In summary, keeping indoor CO2 levels within the acceptable range helps ensure good indoor air quality and the well-being and comfort of occupants.
Why do we measure CO2?
CO2 is often measured in indoor environments to quickly serve as an indication if additional ventilation is required. Because CO2 is a known indoor pollutant, too much CO2 can also affect overall employee performance, productivity, and overall health.
When it comes to CO2 in the workplace, extreme levels of carbon dioxide exposure can create negative health effects particularly in enclosed spaces such as restaurants, breweries, beverage industries, agriculture facilities, laboratories, and many others. Overall, by measuring carbon dioxide in indoor areas you can have control over home, office, and workplace health and safety.
What is an unhealthy level of CO2?
What does high CO2 level exposure feel like?
Here's what it may feel like to be in an environment with high CO2 levels:
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Stale air: Rooms with high CO2 levels often feel stuffy and lacking in fresh air. This sensation occurs because CO2 accumulates when there is insufficient ventilation to bring in fresh outdoor air.
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Difficulty breathing: Some individuals might experience slight breathing discomfort or shortness of breath in areas with elevated CO2 levels. This is especially true for those with respiratory conditions or sensitivities.
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Drowsiness and fatigue: In environments with high CO2, people may feel more tired or experience difficulty staying alert. This can result in reduced productivity and concentration levels.
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Headaches: Prolonged exposure to elevated CO2 levels might trigger headaches in some individuals.
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Poor concentration and cognitive function: High CO2 levels have been associated with reduced cognitive abilities and impaired decision-making.
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Increased heart rate: In some cases, elevated CO2 levels may cause a slight increase in heart rate, particularly in sensitive individuals.
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Nausea and dizziness: In extreme cases of poor indoor air quality with very high CO2 levels, some people may experience nausea, dizziness, or other discomforts.
Example of a High CO2 level Incident
At CO2Meter, our own office encountered an actual CO2 incident. We share this story to provide perspective on what to do should a potential CO2 leak occur and how CO2 monitors served their purpose in being life-saving equipment.
Here's what happened
Our technicians were studying the effects of extremely low temperatures on carbon dioxide sensors. By using dry ice (the solid state of carbon dioxide) they were able to push the temperature of the sensors and the air they were measuring down in order to test changes in accuracy.
After finishing their testing for the day, the techs placed the dry ice samples in the company refrigerator for temporary storage. Bad idea.
The first person to enter the building the next day heard the CO2 alert warning employees of dangerous CO2 levels. All the CO2 detector alarms in the building were signaling a problem. The LCD readout on the alarm nearest the door indicated the CO2 level was 1,500 ppm – safe but noteworthy.
While CO2 levels above 3% (30,000 ppm) are dangerous and would require the building be evacuated, 1,500 ppm only indicated a small problem. However, any CO2 level above 400 ppm in an unoccupied building was still cause for an alarm.
While several rooms showed elevated levels of CO2, none were unsafe to enter. All the outside doors were opened to ventilate the building. But it wasn’t until the first person opened the refrigerator to store their lunch that the CO2 levels jumped up again.
The staff realized it was the dry ice in the refrigerator’s freezer that was off gassing CO2. Our techs hadn’t realized that while the typical temperature in a freezer is 0 degrees Fahrenheit or -18 degrees Celsius, the freezing point of carbon dioxide is -109.2 degrees Fahrenheit, or -78.5 degrees Celsius. The dry ice was melting in the “warm” freezer.
Actually, the term melting isn’t quite accurate. As a solid block of CO2 warms it sublimates, turning directly into gas, rather than melting into a liquid. Other examples of solids that sublimate are iodine, arsenic, naphthalene (what mothballs are made of) and solid air fresheners.
We were all happy that no one was injured and our CO2 alarms worked as intended. But it's important to recognize that even the "CO2 experts” can have a leak once in a while.
Key Factors Influencing Carbon Dioxide Levels Indoors
Carbon dioxide levels can be influenced by a variety of factors, each impacting the concentration of this gas in different environments. Understanding these factors can help manage CO2 levels more effectively:
1. Ventilation
- Air Exchange Rates: Higher ventilation rates generally reduce CO₂ levels by increasing the exchange of indoor air with fresh outdoor air.
- Ventilation System Efficiency: The effectiveness of HVAC systems in circulating and filtering air impacts CO₂ levels. Poorly maintained systems can lead to elevated CO₂ concentrations.
2. Occupancy
- Number of People: The more people present in a space, the higher the CO₂ levels, as humans exhale CO₂ with every breath.
- Activity Level: Higher activity levels (e.g., exercise or movement) increase CO₂ production per person.
3. Sources of CO₂
- Combustion Appliances: Devices like gas stoves, heaters, and boilers release CO₂ as a byproduct of burning fossil fuels.
- Industrial Processes: Certain industries release CO₂ as part of their manufacturing processes.
4. Indoor Plants
- Photosynthesis: Plants absorb CO₂ during photosynthesis, which can help reduce indoor CO₂ levels. However, this effect is generally small compared to other factors.
5. Building Structure and Insulation
- Building Tightness: Well-sealed buildings may trap CO₂ indoors, leading to higher concentrations if ventilation is inadequate.
- Building Materials: Some materials can absorb or release CO₂, though this is typically a minor factor compared to ventilation and occupancy.
6. Outdoor Air Quality
- External CO₂ Levels: Outdoor CO₂ levels can influence indoor concentrations, especially if ventilation brings in air with high CO₂ content.
- Weather Conditions: Weather conditions can affect ventilation and air exchange rates, influencing indoor CO₂ levels.
7. Temperature and Humidity
- Temperature: Higher temperatures can increase the rate of CO₂ emissions from certain sources and influence ventilation effectiveness.
- Humidity: High humidity levels can affect the performance of ventilation systems and indoor air quality.
8. Time of Day and Seasonal Changes
- Daily Patterns: CO₂ levels can fluctuate throughout the day based on occupancy patterns and ventilation practices.
- Seasonal Changes: Seasonal variations can affect ventilation practices and outdoor air quality, impacting indoor CO₂ levels.
9. Building Use and Function
- Purpose of the Building: Different types of buildings (e.g., residential, commercial, industrial) have varying CO₂ generation sources and ventilation needs.
- Usage Patterns: Changes in how a building is used (e.g., increased occupancy, extended operating hours) can impact CO₂ levels.
By understanding these factors, you can better manage CO₂ levels in various environments, ensuring healthier and more comfortable indoor conditions.
The Best CO2 Level Indoor Air Quality Monitors
For more information in indoor air quality monitoring, CO2 levels indoors, or indoor air quality detectors - please visit our contact us or call us at 877-678-4259.
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