What is one characteristic that non-flammable gases share?

Non-flammable gases are defined primarily by their inability to ignite and their lack of support for combustion. This characteristic is crucial in various safety and industrial applications because it means that these gases do not contribute to fire hazards. Understanding this property helps in the safe handling and storage of non-flammable gases, as they can be used without the typical risks associated with flammable substances.

While ease of compression, odor characteristics, or density relative to air may be associated with certain gases, they do not universally apply to all non-flammable gases. This means that while some non-flammable gases can be compressed easily, not all exhibit this trait; similarly, the presence of an odor or specific density is not a defining feature of non-flammability. Therefore, the defining characteristic of non-flammable gases is their ability to neither ignite nor support combustion, making option B the correct choice.