A startup is building a wearable air-quality monitor using a sensing technology that can cheaply detect the presence of chemicals around you in real time. By reporting the information its sensors gather to an app on your smartphone, the technology could help people with respiratory conditions and those who live in highly polluted areas keep tabs on exposure.

Berkeley, California-based Chemisense also plans to crowdsource data from users to show places around town where certain compounds are identified.

Initially, the company plans to sell a $150 wristband geared toward kids with asthma—of which there are nearly 7 million in the U.S., according to data from the Centers for Disease Control and Prevention— to help them identify places and pollutants that tend to provoke attacks,  and track their exposure to air pollution over time. The company hopes people with other respiratory conditions, and those who are just concerned about air pollution, will be interested, too.

In the U.S., air quality is monitored at thousands of stations across the country; maps and forecasts can be viewed online. But these monitors offer accurate readings only in their location.

Chemisense has not yet made its initial product, but it expects it will be a wristband using polymers treated with charged nanoparticles of carbon such that the polymers swell in the presence of certain chemical vapors, changing the resistance of a circuit.

The company hopes to have its first prototypes manufactured in six months. The company’s technology can already detect about a dozen chemicals and compounds, including benzene, hexene, nitrogen dioxide, and carbon monoxide. It is working toward detecting about 19 others.

The technology is currently not nearly as sensitive as Chemisense would like it to be—the company is currently detecting tens of parts per million for a number of compounds, though it’s working toward detecting hundreds of parts per billion. “I think that’s going to be our commercial limit for the time being,” cofounder and CEO Brian Kim says. A municipal air-quality monitoring station, by comparison, would be able to detect between ten and one parts per billion.

Ted Zellers, a chemistry and environmental health sciences professor at the University of Michigan who studies chemical sensing, says that while several different polymers can be used to detect different chemicals, if more than one or two chemicals are present simultaneously the sensor’s ability to detect those chemicals falls “precipitously.” “If three are present, it is highly unlikely that they can tell what is there,” he says.

Additionally, he says, being able to sense chemicals in the hundreds or tens of parts per million range is only marginally useful for detecting exposure in places like offices and homes. “You want to have your detection limits well below what you think you want to measure, at least tenfold below, so you’re not wondering whether you have an actual signal or not,” he says.