Sounds will wake you. Touch will wake you. Light will wake you. But smells won't disturb your slumber. That could spell trouble when there's a fire.

The takeaway: People who can easily detect odors when they are awake and in the early transition to sleep cannot rely on their sense of smell to rouse them from deep slumber to the danger of fire, Science Daily reports of a new study from medical school professors at Brown University in Providence, R.I.

The study: For two nights, six volunteers who were in their early 20s were outfitted with an elastic chinstrap to encourage nose breathing. The researchers tested two types of odors: a pleasurable peppermint and an offensive pyridine, a component of coal tar that is used as an herbicide for firewood and is a likely byproduct of many fires. The odors, which were presented through a tube that was attached to an air-dilution device, were tested during moderately deep Stage Two sleep, deep Stage Four sleep and REM (rapid eye movement) sleep.

The results: None of the six participants responded to the peppermint while they were asleep. The responses to the intense and noxious pyridine were infrequent and did not wake any participants in the deepest stage of sleep. In contrast, a moderately loud sound woke up all the participants no matter which sleep stage they were in.

The paper's co-author Mary A. Carskadon told Science Daily, "As the saying goes, we 'wake up and smell the coffee,' not the other way around."

The study findings were published in the journal Sleep.