Before a manhole cover is removed, the atmosphere within must be tested for which of the following?

When preparing to remove a manhole cover, it is crucial to ensure the safety of personnel by testing the atmosphere inside the manhole. The correct approach involves checking for both oxygen deficiency/enrichment and potentially hazardous gases such as explosive gases and hydrogen sulfide.

Oxygen deficiency can lead to asphyxiation, while oxygen enrichment poses a risk of fire or explosion. Testing for explosive gases is essential because these can ignite in the presence of sparks, leading to potentially deadly explosions. Hydrogen sulfide is particularly dangerous due to its toxicity and the fact that it can produce symptoms very quickly, making it a significant concern in confined spaces like manholes.

By confirming both oxygen levels and the presence of hazardous gases, safety protocols are upheld. Therefore, the need to test for these atmospheric conditions justifies the selection of the combined answer, which encompasses both sets of critical tests for maintaining a safe work environment.