What characteristic of LPG makes it hazardous?

The characteristic that makes LPG (liquefied petroleum gas) hazardous is that it is heavier than air. This property is critical because, when released, LPG tends to accumulate in low-lying areas or confined spaces, creating a risk of explosion or fire due to the concentration of gas. Since LPG can displace oxygen in an environment where it accumulates, it poses a significant risk not just as a flammable substance but also in terms of potential asphyxiation hazards.

In contrast, being lighter than air, having a freezing point of 0°F, or igniting in water does not accurately describe the primary danger associated with LPG. These incorrect characteristics do not reflect the primary behavior of LPG in the atmosphere or its safety profile in fire situations. Thus, recognizing LPG's weight relative to air informs firefighters and emergency responders about the appropriate safety measures to take in the event of a leak or fire involving this gas.