Any potentially dangerous pathogens will not survive in the final fermentation due to the alcohol content. Fermented barley produces ethanol, not the much more dangerous methanol.
In the unlikely event that your homebrew does become unpalatable to the point of making you sick, poor sanitation is the likely culprit.
Even low ABV beer has enough alcohol in it to kill any truly harmful bacteria. On the flipside, fermenting hops produce ethanol, not the significantly more dangerous methanol.
Sanitizing equipment, boiling temperatures, and minimizing the amount of time the brew is exposed to open air contribute to infection control. These processes, if done correctly, should minimize the risk of infection.
Methanol should not be confused with ethanol. Ethanol is produced when yeast ferments malted barley (aka the typical process for brewing beer). In contrast, methanol can be produced by fermenting fruits and vegetables .
The process to convert ethanol into methanol is chemically complex and will not happen accidentally.
To check your beer for potential infection: – Conduct a sniff test – Do a visual check – Give is a taste
Unless you over-consume, as long as the brewer is performing proper sanitization techniques, you should not be at risk of falling ill or dying due to drinking homebrew beer.