Before removing a manhole cover, what must be tested in the atmosphere?

Before removing a manhole cover, it is vital to test for explosive gases, hydrogen sulfide gas, and oxygen deficiency/enrichment. This is critical for safety because manholes can contain hazardous atmospheres due to potential gas leaks or the accumulation of harmful gases.

Explosive gases, such as methane, can pose an immediate risk of explosion when exposed to an ignition source. Hydrogen sulfide is particularly dangerous due to its toxicity and the respiratory hazards it poses, even at low concentrations. Additionally, ensuring an appropriate level of oxygen is present is essential for worker safety; both oxygen deficiency and enrichment can lead to serious health risks. Testing for these specific conditions enables workers to take necessary precautions before entering an enclosed space, thereby preventing accidents and ensuring a safer working environment.