Sensors that smell help save lives everyday. From cars that won't start because court-ordered breathalyzers smell alcohol in the operator's blood stream, to bomb-sniffing machines at the airport, to complex medical tests that analyze your breath - we are designing machines that smell to make the world a safer place.

Smell sensors are essential to the future of the Internet of Things. From RFID stickers capable of smelling food through the package and updating the food's status to the Web, to our next phone being a "smell phone", engineers are finding innovative ways to help protect our families from being exposed to toxic hazards.

  1. Breathalyzers

  2. Sensors that measure blood alcohol content by smelling your breath have been around since 1938 when a professor named Rolla Harger invented the Drunkometer. His success in marketing the device was due in part to his work with the National Safety Council to legislate alcohol limits - as well as legitimize his sensor data as evidence in a court of law. Today, the innovation that's occurring with these sensors is the dramatic decline in cost. So next time you want to know if you're legal to drive after you drink, you can just blow into a Mini-Key chain Breathalyser, a device that will set you back less than $10.

  3. Smell Sensors In Medicine

  4. In Israel, Russell Berrie of the Nanotechnology Institute at Technion developed a sensor that can verify lung cancer by smelling a patient's breath. The sensor searches 42 different lung cancer biomarkers, and is built out of nine cross-reactive chemiresistors. These resistors are built out of gold nanoparticles, each with different organic functionalities. A similar sensor from the same institute can be used to detect kidney disease sooner than traditional urine tests can. The research for that particular sensor system is titled Sniffing Chronic Renal Failure in Rat Model by an Array of Random Networks of Single-Walled Carbon Nanotubes.

  5. Smell Phones

  6. Michael Sailor, professor of chemistry and biochemistry at U.C. San Diego is working with startup Rhevision to develop a smelling device that will attach to your cell phone. The system is based on a camera that takes a picture of porous silicon. Each of these microscopic pores are individually shaped, or tuned, to change color when a specific chemical is encountered. Thanks to the current megapixel resolution of today's phone cameras you can take a single picture of these pores, or sensors, and load it to the Web where it can be analyzed in real time. One application would be that these smell phones could rapidly map out chemical spills and other exposure threats.

  7. RFID That Smells

  8. General Electric is currently testing RFID-configured smell sensors. These small stickers can not only detect the presence of hazardous waste, they can also detect and report food spoilage. One example is a milk carton with an RFID sticker attached to the outside. The sticker periodically smells the milk through the packaging, and as soon as the milk goes bad the RFID sends a wireless alert.

  9. Bomb Smelling Sensors

  10. Ion Mobility Spectrometry machines are currently the most common bomb-smelling sensors in U.S. airports. Austrian manufacturer Ionicon Analytik was recently featured in Scientific America because of its new Ionicon Analytik's Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) machine. This machine is about the size of a refrigerator and is so sensitive that it can distinguish between molecules that are nearly identical. The device works by creating "protonated" water vapor, which is essentially water vapor with extra protons. Many organic compounds, including explosives, have an affinity to grab those extra protons and in turn become positive themselves.The positive ions produced can be extracted and analyzed to reveal their chemical composition.

  11. Non-Destructive Carbon Dating

  12. Traditional carbon dating methods required that a small piece of the object must be destroyed through burning. The carbon is then measured for age based on degeneration of the radioactive isotope Carbon 14. Yet with many artifacts the destruction of even small portions of it is sometimes prohibitive. A new non-destructive method allows the object to be placed a container that is filled with an electrically charged plasma gas similar to the plasma found in a high-definition TV. The plasma gently oxidizes the artifact, which will release trace amounts of carbon dioxide that can then be used for Carbon14-decay analysis.

These six ways are just the tip of the iceberg in terms of what's currently being developed. For example, perspective search service GlobalSpec lists thousands of companies designing gas and chemical sensors. How many of these sensors will one day generate data for the Web? If you have a sense of scenarios that will make this happen, please post your comments below.

Image by Patrick J. Lynch, medical illustrator