Could a test like this detect lung cancer?
A breath-test device which can spot people suffering from lung tumours has been put on trial in Italy.
It has long been suspected that patients with a variety of lung problems give off different chemicals in their breath.
And now scientists at the University of Rome have developed a sensor which, they claim, can detect those chemicals flowing out of a cancerous lung.
Their tests, on a group of 60 people - half with lung cancer - pinpointed every single cancer patient.
They suggested that an 'e-nose' could one day form the basis of a screening test for smokers and others at risk of lung disease.
The only way of doing this reliably at the moment is to use a bronchoscope to look directly at the insides of the lungs for signs of cancer.
Lung cancer patients are known to have higher levels of certain chemicals, called alkanes and benzene derivatives, in their breath.
Other conditions, such as diabetes, asthma, and infections like TB can also produce distinctive chemical signatures.
The sensor array in the e-nose looks for a particular "profile" of chemicals suggestive of cancer.
The test takes approximately a minute to deliver its verdict on the breath of the patient.
Dr Carrado Di Natale, head of the team which developed the device, said it had potential as a screening tool.
"It would be less accurate than bronchoscopy but it would be so much easier," he said.
Most lung cancers are not caught early by doctors and they are far tougher to treat as a result.
Dr Richard Sullivan, from Cancer Research UK, said: "Smell is very important for detecting disease, and this is an interesting twist.
"But the study is far too small to mean anything."
The study was reported in New Scientist magazine.