Decision document for: 2-methy-4-isothiazolin-3-one - CAS No. 2682-20-4 5-Chloro-2-methy-4-isothiazolin-3-one (in combination with 2-methyl-4-isothiazolin-3-one) - CAS No. 26171-55-4 You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more. Inert Reassessment Decision Document for 2-methyl-4-isothiazolin-3-one and 5-Chloro-2-methyl-4-isothiazolin-3-one (PDF)(4 pp, 1 MB)