I'm going to somewhat disagree with the other replies.
Plenty of people heat their homes with kerosene heaters that give off the same emissions as the propane. They run them constantly, even over night so I doubt the concentration of co or co2 from 1 brew will be any worse.
Those are designed for indoor use. The difference in emissions isn't based on what fuel is being burned as much as, how is the burner designed, and how well is it functioning.
CO and CO2 build up are most dangerous when you are sleeping. You just never wake up. I've been on job sites where exhaust levels got too high and you have a burning sensation in your eyes, they need O2. So don't dose off while brewing.
When CO2 gets to your eyes, your throat, anything moist, it condenses and forms carbonic acid. This is where the stinging is coming from, and occurs at around 5000ppm. This is minor CO2 Poisoning, and an indication that you are doing something very foolish already. Its not a good indication of CO however. During any combustion reaction, you get 2 products, CO2 and H2O. Anything else produced is due to an inefficient reaction, or an incomplete reaction.
CO poisoning however, begins at 70ppm, and will kill you at 400ppm.
Burners labeled for outdoor use can produce very toxic levels of CO - because they are meant to be used outdoors where it will diffuse very fast and not become concentrated.
To be able to be used indoors, it has to follow a lot more strict standards. Its silly to compare the two.
Even with what I've stated I would still recommend doing it outside. Throw a tent up and go at it.
Good advice...the problem with CO poisoning is, it'll kill you fast...before you even know its there. The CO can build up in an enclosed space so fast that you skip the headache and vomiting step, and go straight to the passing out and dying step.