There is an old saying in toxicology: the dose makes the poison. What that means is that things can be harmful at higher amounts and not harmful at lower amounts. Unfortunately, that is very old school. Newer research shows that some things have not safe level, and many substances can have stronger or different effects as the dose goes down. See the article in Science News, January 20, 2007, as reported on in the October 2007 issue of Our Toxic Times.
As a practical matter, this adds another layer of complication for those who are hypersensitive to chemicals. You cannot make the assumption that items will out-gas to the point where they will no longer cause reactions.
And always remember — trying to live through an out-gassing may make you hypersensitive to whatever is out-gassing. If that happens — a real hypersensitivity — you will likely never be able to tolerate the item. That is why out-gassing something must be done away from your living space. You cannot just "tough it out" and expect something good to come of it.