Which of the following is NOT a characteristic of flammable gases?

The correct response identifies that a flammable gas does indeed have a flammable range that includes both a lower and an upper limit. In typical characteristics of flammable gases, the flammable range is defined as the concentration of gas in the air that is capable of being ignited. This range consists of a minimum percentage (lower limit) and a maximum percentage (upper limit) of gas that can sustain combustion. An absence of an upper limit does not align with the known behavior of flammable gases, as exceeding the upper limit typically results in the mixture being too rich to ignite.

In contrast to this, the other options correctly describe aspects of flammable gases. For instance, being ignitable at certain concentrations in air is a fundamental characteristic of flammable gases; there are specific thresholds of concentration required for combustion. The characteristic regarding the gas being in a gaseous state at or below 68°F relates to many common flammable gases that are gases under standard atmospheric pressure at lower temperatures. Lastly, the fact that gas can be ignited in a mixture with less than 13 percent by volume illustrates that some gases can ignite at very low concentrations, as long as the conditions are right for combustion to occur.

This understanding is crucial in safety protocols when