Which type of substance does a fume hood primarily protect users from?

A fume hood is specifically designed to safeguard users from hazardous fumes and vapors generated during experiments and various chemical processes. It works by providing a ventilated workspace where toxic or unpleasant vapors can be removed from the air through an exhaust system. This reduces the risk of inhalation and exposure to toxic substances, offering a critical layer of protection for laboratory personnel.

In contrast, the other options do not accurately reflect the primary purpose of a fume hood. Hot liquids may present a burn hazard but are typically managed through other safety equipment, such as personal protective equipment (PPE) and laboratory practices. Biological specimens require different containment measures, like biosafety cabinets, designed to prevent contamination rather than fume management. Sharp objects, while a hazard in any lab setting, are not the focus of fume hood design, which centers around the safe handling of volatile substances. Thus, the primary function of a fume hood is to manage hazardous fumes and vapors, making this the correct choice.