What CO₂ Level Is Dangerous?

Carbon dioxide becomes immediately dangerous at 40,000 ppm. Still, cognitive impairment begins at concentrations as low as 1,000 ppm.

In this guide, we’ll explore the specific CO₂ thresholds that pose health risks. We’ll also cover:

• Regulatory guidelines from major safety organizations
• Cognitive and physiological effects at different concentration levels
• Mitigation strategies for industrial and commercial environments

Occupational Safety Standards for CO₂ Exposure

OSHA sets the permissible CO₂ exposure limit at 5,000 ppm as an 8-hour time-weighted average with a short-term exposure limit of 30,000 ppm for 15 minutes.

NIOSH takes a more conservative approach and recommends a 10-hour time-weighted average of 5,000 ppm with a ceiling limit of 30,000 ppm for 15 minutes. The organization emphasizes that prolonged exposure above these levels can cause respiratory and metabolic strain.

Finally, the American Conference of Governmental Industrial Hygienists sets similar limits with a time-weighted average of 5,000 ppm and short-term exposure limit of 30,000 ppm. These guidelines reflect the organization’s focus on preventing respiratory stimulation and increased heart rate that occur at higher concentrations.

Life-Threatening CO₂ Concentrations and Acute Health Effects

At 40,000 ppm, even a few minutes of CO₂ can cause:

• Respiratory acidosis
• Confusion
• Impaired motor function

At this concentration, the gas disrupts the body’s acid-base balance and interferes with oxygen delivery to vital organs.

Concentrations above 50,000 ppm induce even more severe symptoms like dizziness, headaches, and shortness of breath as the body struggles to maintain normal respiratory function. Workers in confined spaces or areas with poor ventilation face the highest risk of acute exposure at these levels.

At 80,000 ppm and above, CO₂ exposure leads to rapid unconsciousness or death due to severe respiratory depression and metabolic disruption. For perspective, this concentration is 200 times higher than typical outdoor air levels of around 400 ppm.

Even sub-lethal concentrations cause concerning symptoms. Exposure to 30,000 ppm triggers moderate respiratory stimulation and increased heart rate, while levels between 5,000 and 10,000 ppm cause symptoms that can compromise workplace safety, such as:

• Drowsiness
• Headaches
• Reduced attention span

Cognitive Impairment and Indoor Air Quality Thresholds

CO₂ directly affects cognitive function at concentrations well below occupational safety limits, with performance declines beginning around 1,000 ppm.

ASHRAE Standard 62.1-2022 recommends indoor CO₂ levels no more than 700 ppm above outdoor concentrations, typically targeting a ceiling of 1,100 ppm. This standard recognizes that cognitive impairment occurs at much lower levels than acute health effects.

These cognitive effects persist even when other air pollutants are controlled, which means CO₂ directly impacts brain function instead of serving merely as an indicator of poor ventilation.

Mitigation Strategies for Industrial and Commercial Applications

Demand-controlled ventilation systems use real-time CO₂ sensors to automatically adjust airflow and maintain safe levels below 1,000 ppm in occupied spaces. They provide the most effective control for preventing dangerous accumulations in environments like:

• Warehouses
• Production facilities
• Distribution centers

High-efficiency particulate air filtration complements ventilation systems by reducing co-pollutants, though it cannot directly remove CO₂ from the air. This is why proper system design requires both adequate fresh air exchange and filtration to maintain safe working conditions.

Industrial facilities handling CO₂ or dry ice should implement continuous monitoring with alarm systems set at multiple threshold levels. California’s Division of Occupational Safety and Health requires such monitoring in confined spaces where CO₂ concentrations may exceed 5,000 ppm.

Finally, the U.S. Green Building Council advocates for LEED-certified spaces with CO₂ monitors in high-occupancy zones to ensure worker safety and optimal productivity.

Beware of Excessive CO₂ Exposure

Understanding dangerous CO₂ levels requires recognizing both immediate health threats at 40,000 ppm and subtle cognitive impairments beginning around 1,000 ppm, as even these minor impairments can have severe consequences.

As research continues to reveal CO₂’s direct effects on brain function, industrial facilities must balance traditional occupational safety standards with emerging evidence. Implementing comprehensive monitoring and ventilation ensures both worker safety and optimal performance across industrial applications.