A Class C operator is expected to do more than recognize plant hazards — you're expected to run the procedures that control them: calibrating the gas meter before your shift, walking a confined space entry permit from start to finish, and handling chlorine and caustic deliveries correctly. This guide builds directly on WWT Safety: Operator Fundamentals and assumes you already understand why digester gas, confined spaces, and plant chemicals are dangerous. Here, the focus shifts to how the controls actually work.
Digester Gas Composition and the Explosive Range
Digester gas is roughly 50–75% methane (CH4) by volume, with the balance mostly carbon dioxide, plus hydrogen sulfide and water vapor (EPA AgSTAR). The methane fraction is what drives the explosion hazard, and it only matters within a specific concentration band in air:
- Lower Explosive Limit (LEL): 5.0% methane