Sterilization can be achieved through physical, chemical, or mechanical means to eliminate all life forms. Physical sterilization methods include dry heat (such as flaming or hot air ovens), moist heat (such as autoclaving, boiling, or pasteurization), and radiation (such as x-rays or gamma rays). Chemical sterilization uses antimicrobial agents like formaldehyde, halogens, or chloroform. Mechanical sterilization filters microbes from liquids and gases. The most effective sterilization depends on the item and desired outcome.