What does the flame over circle mean?

Flame Over Circle

: This symbol denotes the presence of oxidizers. Oxidizers are substances that enhance combustion, allowing fires to burn more intensely and for prolonged periods.
Flame Over Circle.

Skull and Crossbones

: This symbol refers to hazardous materials, including poisons and highly concentrated acids, which can cause immediate and severe toxic reactions (acute toxicity). Skull and Crossbones.