Portable sensor lets users monitor air pollution on their smartphone


December 19, 2012

The CitiSense sensor provides smartphone users with real-time air quality readings for their immediate environment

The CitiSense sensor provides smartphone users with real-time air quality readings for their immediate environment

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Air quality is one of those things that many of us should be more concerned about, but aren’t. According to some people, this is because we’re not easily able to know how clean the air around us really is – we just assume it’s “clean enough.” Computer scientists at the University of California, San Diego have set out to change that. They’re developing a compact, portable air pollution sensor that communicates with the user’s smartphone, to provide real-time air quality readings for their immediate surroundings.

Known as CitiSense, the device is able to measure local concentrations of ozone, nitrogen dioxide and carbon monoxide, which are the pollutants emitted most by internal combustion vehicles. That data is wirelessly transmitted to the user’s smartphone, where it’s displayed on the screen via a custom app – along with an actual number rating, the display also utilizes the EPA’s color code scale, where green is good and purple ... isn’t.

One of the ideas behind the sensors is that if commercialized, they would allow everyday people to be more proactive when it comes to air pollution. Users could avoid areas where the levels are dangerously high, for example, and would perhaps be more motivated to pressure local authorities to do something about the problem.

Also, data gathered from a multitude of the sensors throughout a region could provide the public with much more detailed and accurate air quality reports than is currently possible. According to the university, although San Diego County measures approximately 4,000 square miles (10,360 sq km), it is currently served by only about ten air-quality monitoring stations.

A prototype of the CitiSense sensor

To test the technology, 30 people were given prototype CitiSense sensors to use in their everyday lives for a period of four weeks. Among other things, the test subjects discovered that air pollution is worse in particular highly-localized areas – it’s not just evenly diluted throughout the air. Not surprisingly, it was likewise noted that certain times of day are more hazardous than others.

Unfortunately for those of us who do our part to reduce pollution, it was also found that people who cycled or waited for the bus along a given route were exposed to more airborne pollutants than those who drove the same route.

The sensors presently cost US$1,000 per unit to build, but the researchers are confident that the price could be greatly reduced by mass production – they could conceivably even be incorporated into commercial smartphones. Although the constant data exchange between the prototype sensors and their paired phones is a considerable drain on the phones’ batteries, that could reportedly be addressed by limiting such exchanges to spaced intervals, or only when requested by the user.

North Carolina-based tech firm RTI International is developing a somewhat similar gadget known as the MicroPEM (Personal Exposure Monitoring device), although it doesn’t provide real-time readings. The University of Southern California has also created an Android app that uses the phone’s camera to measure particulate matter in the atmosphere, but it doesn't determine what those particles consist of.

Source: University of California, San Diego

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

Someone will develop a sampling pump that utilizes individual movement to run it more efficiently. Nano flywheel perhaps?

Gary Richardson

There will be a quick death for the I.C.E. and it will be the emissions. ....not oil shortage. Nanoparticles is my bet.

Stewart Mitchell

Um, don't get me started on a tirade. There's a movement to what I call "cheap and shitty sensors" that provide people misleading information about air quality and divert attention away from the sophisticated and accurate networks we have spent decades to build and perfect. The problem is somebody with an asthmatic kid is going to buy one of those things, it's going to show "green/good", and let their kid play when he shouldn't, and the kid ends up in the hospital.... or someone with a heart condition gets the wrong data and ends up DEAD.

The problem is these sensors are wildly inaccurate (+/- 50% from actual), the monitors don't consider interference of gases and other conditions (humidity, for example), and they data they portray are not accurately linked to the "EPA air quality colors" they claim to use.

I also note they claim " the test subjects discovered that air pollution is worse in particular highly-localized areas." That's because crap like this takes an instantaneous value and compares it to the standard. But the standards are based on various exposure times- an 8-hour rolling average for ozone, 24-hour averages for particulate, etc. If you compare a short-term spike against the ozone "standard" of 75ppb vs. a certified monitoring system that computes the ozone over an 8-hour rolling average (that methodology derived from scientific studies of human exposure effects), then of course you're going to see what looks like "worse" air pollution.

People need to be educated before they make inaccurate statements and provide inaccurate data with shit sensors. They WILL get people killed.

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