To be blown off/away — something is blown away or ripped off by wind or an explosion (physical displacement).
強風で屋根が吹き飛んだ。
The roof was blown away by the strong wind.
彼は爆風で窓ガラスが吹き飛ぶのを見た。
He saw the window glass get blown away by the blast.
子どもの帽子が風ですぐに吹き飛んだ。
The child's hat was immediately blown off by the wind.
To vanish or be dispelled — worries, doubts, or moods suddenly disappear (figurative use).
彼の冗談を聞いて重い空気が吹き飛んだ。
His joke blew away the heavy atmosphere.
合格の知らせで不安がすっかり吹き飛んだ。
The news of passing the exam completely dispelled my anxiety.