Hello Chiron,
re' the smell of fingernail polish remover on the breath whilst fasting I have touched upon before but not in any great detail................
//www.curezone.org/forums/fm.asp?i=1217604


Breath-acetone is a reliable indicator of the onset of ketosis, and where this acetone-breath is accentuated and made much worse by the degree of toxins released into the digestive tract overall: especially in the early stages.

This is quite normal and a by-product of the onset of ketosis.
The more foul the breath and the more coated a tongue then the more toxemic the individual and the greater need for the fast in eliminating toxemia.

I am not sure what you mean though about the sense of smell being a danger signal, or even a danger to what and why.
Acetone breath is quite normal really during the fasting process until the latter stages when these acetone bodies disappear.

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EDIT...
"What, then, becomes of those acetone bodies about which we hear so much? That they do show up in a fast is not denied. But we have a different explanation for them. One of the surest signs that the fast is nearing its end is the disappearance of acetone from the breath, urine and excreta. The presence of acetone is part of the ketosis that fasting is said, in some quarters, to produce.

Ketosis is the presence in the blood of certain end-products of fat-metabolism, known as ketones. There are three ketones--acetone, aceto-acetic and beta-oxybutyric acid. The presence of these bodies in the blood is said to produce acidosis and damage the body. The damages that these ketones produce are never described and those who have had most experience with fasting have never seen them. It would be interesting to see a catalogue of the evils that flow from the presence of these bodies. Dr. Gian-Cursio, who says he has never seen any evidence of harm from the presence of these bodies, and who thinks of them as evidences of normal adjustment to the fasting state, says that "their absence would be cause for alarm."
http://www.soilandhealth.org/02/0201hyglibcat/020127shelton.III/020127.ch20.htm


Regards

Chrisb1.