What is the LEL & HEL for CH4, CO2, O2 & H2S, for monitoring of a start-up of a anaerobic digester?

Question

the digester caters for sewage sludge.

Answer 1

Methane LEL 5%   UEL 15 %

Hydrogen sulphide  LEL 4%     UEL 44

As you will not be sure the atmosphere is homogeneous, it is safer to be no higher than 25% of either LEL

By the way, H2S is a health hazard to people at concentrations far less than the LEL

CO2 and O2 are not flammable, so have no flammable limits.