Jana is working on her car in the garage because it is cold outside. She begins to feel sleepy and nods off. Just then her father comes into the garage and tells her she forgot to shut off the kerosene heater, and she is lucky to be alive. She exclaims that she did not smell any fumes. Briefly explain how her olfactory system let her down in this instance.

What will be an ideal response?

Answers will vary. A sample answer follows. The olfactory system usually picks up odorants, which are volatile chemicals in the air. In this way, our sense of smell is an early warning system, allowing us to detect potentially harmful or helpful substances before we come into direct contact with them. However, our olfactory system does not respond to all airborne chemicals. Carbon monoxide molecules, such as those produced by the heater, are not detectable by the olfactory system and can become dangerous without warning, which is what happened to Jana.