Final answer:
A sign of a possible backdraft or smoke explosion includes smoke-stained windows, puffing smoke, and dense, discolored smoke, signaling a potential for extreme danger.
Step-by-step explanation:
A sign of a possible backdraft or smoke explosion situation includes observing windows that are stained with smoke but not broken, smoke coming out in puffs which is indicative of the fire's intake of air, and smoke that is unusually dense and yellowish or brownish. These signs hint at an uncertainty over whether a serious fire or hazard awaits after an alarm and the potential for extreme physical danger. It's essential to approach such situations with extreme caution.
Warning: When working with Bunsen burners, always be aware of the risks of open flames and high-temperature combustion, which could trigger a dangerous reaction if not handled correctly.