As little as 5 parts per billion
Sensitives react to such a tiny amount that non-sensitives often have difficulty understanding.
5 parts per billion is like five squares of toilet tissue in a roll that stretches from New York to London..jpg)
It's the same as 5 drops of bleach in an olympic size swimming pool or 5 seconds in almost 32 years.
What that means for those affected is that the fumes linger - long after the substance has been applied. Non-sensitives have trouble believing that sensitives react to such small traces, but we do.
Japanese Researchers looked into that, click to read the study.