Methods, apparatuses, and systems for monitoring gas leaks are disclosed herein. An example Heating Ventilation and Air Conditioning (HVAC) may comprise: a sampling tube fluidly coupled to a first opening defined in a conduit; and a sensor assembly fluidly coupled to the sampling tube. The sampling tube is positioned exterior to the conduit and extending along a direction of a gravitation force. The sensor assembly is configured to receive one or more gases that have a greater density in comparison to the ambient air and sense the one or more gases to generate a signal.