Cyanide can have both acute (large single event exposure) and chronic (long term low exposure) effects
Inhalation or ingesion of high concentrations of cyanide causes apnea, coma and cardiac arrest with death following in a matter of minutes.
At lower doses, loss of consciousness may be preceded by general weakness, giddiness, headaches and dizziness. Skin colour goes pink from high blood oxygen saturation.
Cyanide at low levels can impact blood chemistry.