Which gas is more dangerous at 400 ppm, H2S or CO, and why?

H2S (hydrogen sulfide) is indeed considered more dangerous at 400 ppm than CO (carbon monoxide) primarily due to its lower Immediately Dangerous to Life or Health (IDLH) values. The IDLH for H2S is significantly lower than that for CO, indicating that exposure to H2S at this level poses a much greater risk to life and health.

In practical terms, the IDLH for H2S is approximately 100 ppm, while for CO, it is higher at around 1,200 ppm. This means that even relatively lower concentrations of H2S can result in severe health effects or even death, showcasing its acute toxicity. Understanding the IDLH values is crucial for the safety of mine workers, as it informs them of the levels at which a substance becomes immediately hazardous to human health.

Although CO is colorless and can be dangerous due to its inability to provide sensory input about its presence, this factor does not influence the immediate risk associated with the specific concentration being discussed. Similarly, detection methods for H2S make it easier to identify, but this does not imply that it is safer at the specified concentration. Overall, the toxicity level associated with H2S makes it a greater danger at 400 ppm