Never mix 84 bleach with toilet cleaner — it produces toxic fumes.
Tips
history
Named after 1984, the year it was developed at Beijing Ditan Hospital to fight Hepatitis B. The '84' is just the year — read it 'bāshísì', not as separate digits.
mistakes
DO NOT mix with toilet cleaner (洁厕灵) or acidic cleaners — produces chlorine gas. This warning is repeated in every Chinese supermarket and school.