The professionals, in this forum, such as my self, 35 years HVAC engineer and technician, have no problem using gas burners indoors. Good ventilation no worries.
The know it all's, armed with half info cry a lot. You can find the same burners mounted on a frame, says for outdoor use only, and the same burner sold for commercial kitchen use (indoors). The outdoor only burner relives the seller of most liability, the indoor burner will have tags all over it, must be installed by a professional.
I am sure most people don't know it takes CO level of 200 PPM to become dangerous, so simply, if your standing there brewing and become woozie, dizzie, sick to you stomach, you may have a problem. Most people die from CO poisoning in their sleep from a faulty furnace.
Ask a professional for help if your not sure, but you can use gas appliances indoors.