Ditch the mints! Thumb-sized ‘sniffing’ sensor can detect if you have BAD BREATH by testing for hydrogen sulfide in your exhaled air 

  • South Korean team’s prototype device detects hydrogen sulfide on breath
  • Hydrogen sulfide is made by oral bacteria and is known for its pungency ‘odor
  • The presence of H2S, or bad breath, can then be displayed on a smartphone app

In case you forgot the mints on a first date, scientists have created a portable, thumb-sized prototype device that quickly ‘sniffs’ out bad breath.

The device, created by experts in South Korea, detects the presence of hydrogen sulfide (H2S) – the gas that causes bad breath.

After exhaling into the device, the presence of the H2S on the breath can be displayed on the accompanying smartphone app.

As well as a social impurity, bad breath is a natural warning sign of potentially serious dental problems.

Paper image from Korean experts shows how device could offer rapid detection of hydrogen sulfide in human breath

The study has been carried out by experts from Samsung Electronics and Korea Advanced Institute of Science and Technology (KAIST) in Daejeon, South Korea.

Continuous monitoring of hydrogen sulfide (H2S) in human breath for early-stage diagnosis of halitosis [bad breath] is of great importance for the prevention of dental diseases,’ they say in their paper.

‘This study offers possibilities for the direct, highly reliable and rapid detection of H2S in real human breath without the need for any collection or filtering equipment.’

H2S is made inside the body in small doses – and is probably best known for carrying Pungent smell of rotten eggs.

H2S and other foul-smelling sulfur byproducts are excreted as waste by bacteria on the tongue and below the gum line.

Unfortunately for those around us, they are present in the air we exhale, making good oral hygiene on a first date or job interview important for combating odor.

Why can’t you smell your breath by blowing into your hand

Contrary to popular belief, you cannot test your breath by blowing into your hand. According to dentist and bacteriologist Dr. Howard Katz, founder of The Breathe Company, it simply doesn’t work.

Your body is designed in such a way that you cannot detect your own smell and your senses become used to the smell of your own breath.

It’s a process called adaptation that we’ve developed over centuries of evolution—it helps us be able to recognize strange odors quickly without being overwhelmed by our scents.

You constantly exhale, so you become accustomed to your smell.


Previously, some instruments were able to measure small amounts of H2S, but they required exhaled air to be collected and tested on expensive equipment in the laboratory, which is not feasible for consumers.

Previous studies have shown that when some metal oxides react with gases containing sulfur, their electrical conductivity changes.

And when metal oxides are combined with noble metal catalysts, they can become more sensitive and selective.

Therefore, to develop a small, real-time bad-breath analyzer, the team wanted to find the right combination of substances that could elicit the fastest and strongest response to H2S directly in air.

The researchers mixed sodium chloride (an alkali metal salt) and platinum (a noble metal catalyst) nanoparticle with tungsten.

They then electrospun the solution into nanofibers which they heated, converting the tungsten to its metal oxide form.

Electrospinning is a method to produce ultra-fine fibers measuring as small as one billionth of a meter in diameter (a nanometer).

In initial tests, hydrogen sulfide had the greatest reactivity in composites made of equal parts each metal, which the team measured as a large reduction in electrical resistance in less than 30 seconds.

Although this nanofiber reacted with some sulfur-containing gases, it was most sensitive to H2S.

This produced 9.5 and 2.7 times greater reactivity than dimethyl sulfide or methyl mercaptan, respectively, which also contain sulfur.

As well as a social misconception, bad breath is a natural warning sign of potentially serious dental problems.

As well as a social misconception, bad breath is a natural warning sign of potentially serious dental problems.

In the end, the team coated the interdigitated gold electrode with nanofibers and connected the gas sensor with humidity, temperature and pressure sensors to their tiny prototype.

The device correctly detected 86 percent of bad breath when people’s breath was exhaled directly on it.

While this device is yet to be commercialised, it can be incorporated into much smaller devices such as key rings for quick and easy self-diagnosis of bad breath.

A detailed description of the system is given in the team’s paper published in the journal ACS Nano.

Causes of bad breath (Halitosis)

There are several possible causes of halitosis:

poor oral hygiene

This is the most common reason. Bacteria that build up on your teeth — especially between them — as well as on your tongue and gums, can cause unpleasant-smelling gases. These bacteria are also responsible for gum disease and tooth decay.

Food & Beverage

Eating strong-tasting foods like garlic, onions and spices is likely to cause bad breath. Strong-smelling drinks like coffee and alcohol can also cause bad breath.

Bad breath caused by eating and drinking is usually temporary. Good dental hygiene will also help.


As well as making your breath smell, smoking stains your teeth, irritates your gums, and impairs your sense of taste.

It can also significantly affect the development of gum disease, which is another major cause of bad breath.

crash dieting

Crash dieting, fasting and low-carbohydrate diets are another possible cause of bad breath. They cause the body to break down fat, which produces chemicals called ketones that can be smelled by your breath.


These include: Nitrates – these are sometimes used to treat angina; certain chemotherapy drugs; and tranquilizers (phenothiazines).

If a medication you’re taking is causing bad breath, your GP may…


Mail Us For  DMCA / Credit  Notice

Recent Articles

Stay on top - Get the daily news in your inbox

Related Stories