What is the maximum allowable concentration for CO in a 10-hour work shift if derived from a foundational TWA?

• A. Higher than 25ppm
• B. Equal to 25ppm
• C. Less than 25ppm
• D. Not specified

Answer: (C)

The maximum allowable concentration for carbon monoxide (CO) during a 10-hour work shift is established based on the threshold limit values (TLVs) provided by health and safety organizations. For CO, the time-weighted average (TWA) concentration is often set at 25 parts per million (ppm) for an 8-hour exposure. When considering longer shifts, such as 10 hours, the allowable limits are typically adjusted to ensure that the overall exposure does not exceed safety thresholds.

Setting the maximum allowable concentration for CO at less than 25 ppm ensures that workers are protected from the harmful effects of this gas, which can include headaches, fatigue, dizziness, and potential long-term health impacts. This precautionary approach recognizes that even levels below the TLV can lead to cumulative exposure risks over extended periods. By maintaining a concentration under 25 ppm, safety measures are upheld to prevent health hazards associated with carbon monoxide exposure during shifts longer than the standard 8 hours.

In comparison, the other choices either suggest a higher concentration or do not specify an allowable level, which would not align with the established safety guidelines for workplace exposure limits. The emphasis on keeping the concentration lower than the established 25 ppm contributes to a safer working environment and reflects the proactive measures