What is the highest level of carbon monoxide that can be lethal within three minutes of exposure?

The correct answer highlights the critical danger posed by carbon monoxide at elevated concentrations. At levels of 12,800 parts per million (PPM), exposure can lead to rapid and severe health consequences, including lethality within just a few minutes. This is due to carbon monoxide's ability to interfere with the blood's capacity to carry oxygen, ultimately leading to acute hypoxia and potential fatality.

Concentrations lower than this, while still dangerous, typically result in symptoms of poisoning that can escalate over longer exposure times rather than causing immediate death. For example, exposure to 8,000 PPM is certainly harmful and can cause severe symptoms quickly, but it does not have the same immediate lethality associated with the higher concentration noted in the correct answer. Understanding these thresholds helps in identifying and mitigating risks associated with carbon monoxide exposure in residential and industrial environments.