• They have a cold, allergies, sinus congestion, or another       medical condition.
• Their sense of smell is reduced due to use of tobacco,         alcohol, or drugs.
• Tobacco smoke, cooking odors, and other strong odors can   mask the smell of propane.
• As people age, their sense of smell can become less         sensitive.
• If the smell of propane is present in the air over a period of   time, “odor fatigue” can occur. The nose “gets tired,” and a     person no longer smells the propane odor.

• The propane smell may not be strong enough to wake up     someone who is sleeping.
• The propane smell may be in a location (basement or attic)   where it is not detected by people in other areas of the       building.
• A phenomenon called “odor loss” can occur—an unintended   reduction in the concentration of the odor of propane.

• Air, water, or rust in a propane tank or cylinder can reduce     propane odor concentration.
• The propane odor may stick to the inside surfaces of gas     piping and distribution systems and possibly other materials.

• If the propane is leaking underground, its passage through     soil may reduce the smell of propane.
• Since there is a possibility of odor loss or problems with       your sense of smell, you should respond immediately to       even a faint odor of gas.