Derf said:
Carbon dioxide and water vapor are the only byproducts you should have coming out of the iolite.
Butane should be combined with Oxygen and completely break down
2(C4H10) + 13(O2) -> 8(H2O) + 10(CO2)
The optimal scenario above is for the combustion reaction of butane and O2. The iolite is uses a catalytic reaction to produce heat. I estimate the smell is partially reacted hydrocarbons.
Published literature about catalytic heaters indicates
the catalytic reaction of gas fuel (propane or butane) is inefficient and will create byproducts. In the example below, carbon monoxide (CO) was generated.
"CO EMISSIONS FROM A PORTABLE PROPANE
CATALYTIC HEATER
Catalytic heaters generate heat through a flameless catalytic reaction involving propane [or butane] and
oxygen. This is different from infrared radiant heaters, which generate a flame during the combustion
process. The catalytic heater generates heat by bringing the propane and oxygen (air) into contact with a
platinum catalyst. A chemical reaction then occurs in which the propane and oxygen are converted
primarily into carbon dioxide and water vapor. During the chemical reaction, heat is also released. The
chemical reaction occurs at a temperature well below the flame temperature of typical infrared radiant
heaters. In order to start the reaction, the fuel and air mixture must be ignited by an external heat source,
such as a spark or pilot light.
When the catalytic heater was operated at the test conditions specified, the steady state CO concentration ranged from 67 ppm to 109 ppm."
http://www.cpsc.gov/library/foia/foia05/os/co03.pdf