A peroxyformic acid forming composition comprising: a) a first reagent that comprises an ester of a polyhydric alcohol and formic acid, wherein the ester comprises glycerol formates, pentaerythritol formates, mannitol formates, propylene glycol formates, sorbitol formates or sugar formates and b) a second reagent that comprises hydrogen peroxide or that comprises a substance that generates hydrogen peroxide when in contact with a liquid, wherein 1) said first reagent and said second reagent are kept separately prior to use, and when it is time to generate peroxyformic acid, said first reagent and said second reagent are configured to be contacted with each other to form a liquid that comprises peroxyformic acid and has a pH below 11, and pH of the formed liquid becomes 8 or lower within 1 minute after the contact between said first reagent and said second reagent; or 2) said second reagent comprises a substance that generates hydrogen peroxide when in contact with a liquid, said first reagent and said second reagent are comprised in a solid composition, and when it is time to generate peroxyformic acid, said solid composition is configured to be contacted with a liquid to form a liquid that comprises peroxyformic acid and has a pH below 11, and pH of the formed liquid becomes 8 or lower within 1 minute after the contact between said solid composition and said liquid. a) a first reagent that comprises an ester of a polyhydric alcohol and formic acid, wherein the ester comprises glycerol formates, pentaerythritol formates, mannitol formates, propylene glycol formates, sorbitol formates or sugar formates and b) a second reagent that comprises hydrogen peroxide or that comprises a substance that generates hydrogen peroxide when in contact with a liquid, wherein 1) said first reagent and said second reagent are kept separately prior to use, and when it is time to generate peroxyformic acid, said first reagent and said second reagent are configured to be contacted with each other to form a liquid that comprises peroxyformic acid and has a pH below 11, and pH of the formed liquid becomes 8 or lower within 1 minute after the contact between said first reagent and said second reagent; or 2) said second reagent comprises a substance that generates hydrogen peroxide when in contact with a liquid, said first reagent and said second reagent are comprised in a solid composition, and when it is time to generate peroxyformic acid, said solid composition is configured to be contacted with a liquid to form a liquid that comprises peroxyformic acid and has a pH below 11, and pH of the formed liquid becomes 8 or lower within 1 minute after the contact between said solid composition and said liquid. 1) said first reagent and said second reagent are kept separately prior to use, and when it is time to generate peroxyformic acid, said first reagent and said second reagent are configured to be contacted with each other to form a liquid that comprises peroxyformic acid and has a pH below 11, and pH of the formed liquid becomes 8 or lower within 1 minute after the contact between said first reagent and said second reagent; or 2) said second reagent comprises a substance that generates hydrogen peroxide when in contact with a liquid, said first reagent and said second reagent are comprised in a solid composition, and when it is time to generate peroxyformic acid, said solid composition is configured to be contacted with a liquid to form a liquid that comprises peroxyformic acid and has a pH below 11, and pH of the formed liquid becomes 8 or lower within 1 minute after the contact between said solid composition and said liquid.