Sorry just reading back on previous posts.
 
The Chili oil i use is listed as 8% garlic, its peanut oil, i leave it outside in 30C plus for months on end - never a problem, I have used it for stir fry and Asian style cooking for 15 years now.  If you pre-"boil" Garlic in fresh oil the risk is nil, possibly depending on the type of oil, i think.

Rancid or overly used oil is an issue in Thailand and SE Asia in general, it saves money and adds that lived in taste, I am sure its the same in places like Bangladesh and India and THERE ARE health issues with this. I would assume that BIRs use it as a matter of course, its seems to me a natural progression, though any self respecting BIR would not admit that to its use due to the possibility of H&S breathing down their necks an issue if they are using "American" oils.

Reusing too many times lowers the smoke point, think of it as loosing its elasticity, which is why garlic etc. will not burn and a deep taste results because high temperatures are not reached and germs are not killed, especially in hot, humid climates, especially in Asia/BIRs where a quick stir fry is the Modus Operandi. It only became an issue with the availability of cheaper oils like Rapeseed, Canola, corn became available as a cheap alternative to the "bad" oils like Ghee, Peanut and Coconut.

Infused fresh oil used only once, followed by a hot re-fry will reach the temperatures required and not suffer from this "Hidden" issue.

Any doubts? Look up Botulism / 120C and then further research the smoke point of the oil you are using. I assume you are, like, stir frying your curries?

Always use PEANUT OIL!!!!!!! and not American inventions (Coconut oil if you like your Sri Lankan).