Dense gases are heavier than air and form the largest group of dispersing substances in industrial environments. They flow downward due to gravity and can travel long distances before dilution, making them particularly dangerous.
The dispersion characteristics of dense gases follow terrain gradient - they fall like a waterfall and flow like water. They are not easily distorted by wind and can enter basements, tunnels, and wells, creating significant safety hazards.
Examples of dense gases include heavier-than-air gases, vapors from evaporating liquids, and cold gas clouds that are initially dense but become buoyant as they heat up. Understanding this behavior is critical for proper detection strategy.
Detection strategy requires mounting detectors close to the ground, positioned in the presumed pathway of gas clouds. Consider structures, walls, and dikes that alter flow. Account for cold gas behavior - initially dense, then becoming buoyant as they heat.
Dense gas clouds are extremely dangerous because they can disappear into confined spaces where countermeasures are difficult once gas enters structures. However, migration paths are predictable, making detector placement straightforward if you understand the gas behavior.
Visual indicators may include condensation of water vapor, producing visible fog in cold dense gas clouds. Proper placement based on dense gas dispersion modeling ensures detection before gases enter structures or confined spaces.