How would you best describe chlorine gas?

Chlorine gas is best described as heavier than air. This characteristic is important to understand because, in case of a chlorine leak, the gas will tend to accumulate in low-lying areas due to its density. This can pose significant safety hazards, as concentrations can increase quickly in enclosed or poorly ventilated spaces.

Understanding the physical properties of chlorine gas is critical for wastewater treatment operators, particularly in handling and emergency response scenarios. The gas is also recognized for its pungent yellow-green color and strong, distinctive odor, which makes it detectable even at low concentrations—helping in identifying potential leaks.

The incorrect options highlight aspects that do not accurately represent chlorine gas: it is certainly not odorless and non-toxic; in fact, chlorine gas is both harmful and a respiratory irritant at elevated concentrations, which underscores the need for proper safety measures when handling it.