What is the maximum allowable level of carbon monoxide (CO) in air?

What is the maximum allowable level of carbon monoxide (CO) in air?

• A. Less than 100 ppm
• B. Less than 5 ppm
• C. Less than 35 ppm
• D. Less than 350 ppm

Answer: (C)

CO is toxic and can impair the body's ability to deliver oxygen to tissues. Because of this, air in occupied spaces is kept below a level that would quickly cause symptoms or health risk. A common safety benchmark used for indoor and occupational air is 35 parts per million. This limit provides a practical safety margin to prevent symptoms like headaches, dizziness, or more serious harm during typical exposures, and it aligns with widely used public health standards for short-term exposure. Levels well above that (such as 100 or 350 ppm) would pose a clear poisoning risk in a short period. A value as low as 5 ppm would be unnecessarily restrictive for everyday operations and is not what is typically used as the safety ceiling. So, the maximum allowable CO in air in this context is 35 ppm.

CO is toxic and can impair the body's ability to deliver oxygen to tissues. Because of this, air in occupied spaces is kept below a level that would quickly cause symptoms or health risk. A common safety benchmark used for indoor and occupational air is 35 parts per million. This limit provides a practical safety margin to prevent symptoms like headaches, dizziness, or more serious harm during typical exposures, and it aligns with widely used public health standards for short-term exposure. Levels well above that (such as 100 or 350 ppm) would pose a clear poisoning risk in a short period. A value as low as 5 ppm would be unnecessarily restrictive for everyday operations and is not what is typically used as the safety ceiling. So, the maximum allowable CO in air in this context is 35 ppm.