Imagine a phone app that warns you in advance of potentially dangerous air pollution at your location. That’s one proposed benefit from wearable air monitors under development by a California-based startup, Chemisense.

The monitors will track about a dozen pollutants, including carbon monoxide, sulfur and nitrous oxides, organic volatiles like benzene and ozone. Sensors in the device use polymer-embedded charged carbon nanoparticles that swell in the presence of certain vapors, causing a measurable change in electrical resistance. Readings can be displayed on a smart phone.

Air quality data are also sent to a cloud-based database, where they are combined with data from other wearers and fixed location sensors to generate street-level pollution maps.

According to Chemisense, air quality often changes from street to street, so the ability to identify and characterize pollutants at a specific location is especially important for asthma sufferers, babies and elderly people suffering from pulmonary disease. Existing sensor technology can detect tens of parts per million, a limit Chemisense says it plans to increase to hundreds of parts per billion.

The company’s initial market focus is the seven million children in the U.S. with asthma. Initial prototypes – housed in a wristband - are expected to be out within six months.