What is one warning signal of possible backdraft conditions?

One important warning signal of possible backdraft conditions is smoke-stained glass. When glass becomes discolored due to prolonged exposure to smoke and extreme heat, it is an indicator that there has been significant thermal buildup inside a structure. This staining suggests that the area has reached temperatures that could facilitate a backdraft situation, particularly if volatile gases are present and have not yet ignited.

Backdraft occurs when a fire has consumed all the available oxygen in a confined space while still producing flammable gases; when fresh air is suddenly introduced, it can lead to an explosive ignition. The presence of smoke-stained glass serves as a tangible indicator that these dangerous conditions may exist inside, alerting firefighters to the possibility of a highly explosive situation upon entry.

Other conditions listed, while potentially indicative of other fire phenomena, do not directly suggest the imminent risk of a backdraft in the same direct manner that smoke-stained glass does. For example, smoke flowing from openings may indicate a well-ventilated fire rather than a backdraft, and shattered or opened windows may have various causes unrelated to backdraft conditions specifically.