Carbon dioxide (CO2) is not generally found at hazardous levels in indoor environments. However, elevated levels of CO2 in enclosed spaces can be hazardous to human health. The following are some CO2 levels and their corresponding effects:

• 400 ppm: This is the normal outdoor air level of CO2.
• 1,500 ppm: This level only indicates a small problem.
• 3,000 ppm: At this level, occupants may experience drowsiness and poor air quality.
• 5,000 ppm: At this level, occupants may experience headaches, dizziness, and nausea.
• 40,000 ppm (4.0%): This level is immediately dangerous to life or health (IDLH) .
• 50,000 ppm: This level is IDLH.

The Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit (PEL) for CO2 of 5,000 ppm over an 8-hour workday. The Minnesota Department of Health has set workplace safety standards of 10,000 ppm for an 8-hour period and 30,000 ppm for a 15-minute period. It is unusual to find such continuously high levels indoors and extremely rare in non-industrial workplaces.

It is important to note that CO2 levels in the blood can also be measured through a CO2 blood test. The normal range for CO2 in the blood is 23 to 29 milliequivalents per liter (mEq/L) or 23 to 29 millimoles per liter (mmol/L) . Results outside this range may indicate a problem with the kidneys or lungs.

Overall, it is important to monitor CO2 levels in enclosed spaces to ensure the health and safety of occupants.