Odor threshold is the lowest concentration at which a chemical's odor is detectable by humans.

• A. Odor threshold
• B. Permissible exposure limit
• C. Immediate danger to life and health
• D. Occupational exposure limit

Answer: (A)

This item centers on the idea of a sensory detection limit for a chemical’s smell. The odor threshold is defined as the lowest concentration at which humans can detect the odor. It’s about perception, not safety or health standards.

Permissible exposure limit and occupational exposure limit are regulatory targets set to prevent health effects over a work shift; they tell you how much of a chemical workers should be exposed to, not whether you can smell it. Immediate danger to life and health describes a hazard level where life or bodily function is at risk, which is about safety risk, not odor detection. So, the term that matches the concept of detecting smell at the lowest concentration is the odor threshold itself. Keep in mind that odor thresholds can vary between people and compounds, so odor detection isn’t a reliable measure of safety.