A method and apparatus are disclosed for assessment of a sealed package. Light is emitted from a narrow-band laser source towards said package from outside of said package. An absorption signal of said light scattered in said package is measured, wherein said absorption is caused by said at least one gas when said light is scattered and travels in said sealed package. Measuring is made outside of said package, whereby said assessment is non-intrusive with regard to said package. It is determined if a deviation exists from a predetermined, expected gas composition and/or concentration of said at least one gas within said sealed package based on said measured absorption signal. Thus sealing of said package for said gas is detected.