Final answer:
When evaporating benzyl alcohol for ketamine extraction, it is best to do so in a well-ventilated area.
Step-by-step explanation:
When allowing benzyl alcohol to evaporate for ketamine extraction, it is important to choose the right environment. The best option is to evaporate it in a well-ventilated area. This ensures that any volatile fumes produced during the evaporation process can disperse safely, reducing the risk of inhalation or other health hazards.