Many homebrewers brew beer in their garage frequently to avoid poor weather or extreme temperatures outside.
While brewing beer in the garage should not cause any negative impact with the beer, using a propane burner indoors is considered unsafe.
Unfortunately, the most common heat source that homebrewers use outside of the kitchen is a propane burner. While they do a great job outdoors, these burners are not designed to be used inside a house or even an enclosed area with a ceiling, such as a garage.
While you could use something like an electric hotplate or even a butane burner, these options are way less practical from a brewing standpoint than using a traditional propane burner.
Anytime there is an open flame you will have to worry about the possibility of something catching fire.
Carbon monoxide can be extremely deadly so you should always watch out for symptoms of exposure: – Headache – Nausea – Dizzine – Breathlessne – Fatigue/Sleepine – Collapse – Loss of consciousness
Anecdotally, keeping the garage door open and ensuring that there is proper ventilation has worked well for many homebrewers. Still, there will always be a risk of running a propane heater inside a garage.