Where must pressure relief valves be arranged to ensure safety?

Pressure relief valves are critical safety devices used in systems handling compressed natural gas (CNG). They are designed to release excess pressure from tanks or pipelines to prevent catastrophic failures or explosions. To ensure safety, these valves must be arranged in a manner that directs escaping gas away from buildings and populated areas. This is vital because if gas were to leak or be released, it could accumulate near structures or become a fire hazard, posing significant risks to life and property.

The option that emphasizes the importance of directing the gas away from buildings is therefore the most appropriate choice. By ensuring that escaping gas does not contact structures, the risk of potential ignition and resulting damage is significantly reduced.

Arranging pressure relief valves in a way that ensures safety involves considering factors such as wind direction and the positioning of nearby facilities. Other options, while they may touch upon important considerations in gas management, do not directly address the critical aspect of maintaining safe conditions concerning human and building exposure.