Which of the following is a measure taken to prevent H2S odor during sewer maintenance?

While dislodging slime can help mitigate odors by removing organic material that may contribute to odor production, using chemical deodorants is a more direct and effective measure specifically designed to prevent hydrogen sulfide (H2S) odors during sewer maintenance. H2S is a common byproduct of anaerobic decomposition in sewers, and chemical deodorants can neutralize or mask the odor effectively.

Moreover, increasing the flow rate can disperse odors, but this is not a reliable method for controlling H2S specifically and may not be feasible in all situations. Covering open manholes is a safety measure and might help contain odors to some extent, but it does not actively prevent H2S production.

Using chemical deodorants is a targeted approach to odor control, making it a best practice for sewer maintenance operations aimed at mitigating H2S odors.