In the world of citizen science, air quality and water quality are hot topics. Urban planners, medical researchers and residents are seeking data to better understand the problems of climate change and pollution. A recent post by the Baltimore Sun highlighted the efforts of a group building their own air quality monitors to understand the city’s heat island issue. In the case of Baltimore Open Air, it really does take a village—there are climate change researchers, engineers, and some newly trained technicians from Civic Works. Of course my curiosity was focused on the monitors, so I decided to reach out to the team behind the project. Luckily they found time in between studies and soldering to give me some answers.
Why did you decide to create the monitor? Was there something specific to Baltimore you were checking?
We created our monitor—which we’re calling a WeatherCube—because we’re interested in understanding how air quality varies throughout the Greater Baltimore region. While local air quality has been improving in recent years, the Baltimore area currently has a non-attainment status from the EPA (meaning that we have exceeded the legal limits for what is considered healthy) for two key pollutants: ozone and sulfur dioxide. Like many areas in America, we’re only monitored by a few air quality monitoring stations, because while regulatory-grade air quality monitoring stations are incredibly accurate they’re also very very expensive. Being able to map air quality with better spatial resolution, even with some loss of measurement resolution, can better help us understand how our air varies within cities, how much pollution is where, and ultimately understand how this may affect our health.
Were you inspired by an existing open source environmental monitor?
Before beginning this project our team lead, Anna Scott, looked at a lot of personal air quality monitors on the market, but couldn’t find anything that fit her need for an affordable, outdoor-ready device with aspirated temperature and humidity measurement and capable of measuring what the EPA calls “criteria air pollutants” (such as sulfur dioxide and ozone). And while the indoor air quality monitoring market gives consumers a lot of options, the inner workings and performance benchmarks of most commercial devices aren’t well-documented publicly. Anna began talking with team member Chris Kelley, who builds low-cost, open-source water quality monitoring platforms, about an air quality monitoring collaboration that would be fully open in design and data sharing.
What parts did you use for your monitor?
The WeatherCube uses an ATMega328P (the same chip an Arduino Uno uses) as its main microprocessor, and also uses an ESP8266 for wifi connectivity. Its main circuit board has 128Kb of external EEPROM for storing readings in between data transmissions, and an MCP79412 real-time clock with battery backup. A separate analog signal processing board uses four LMP91000 analog front-end chips, each dedicated to a different SPEC air quality sensor (O3, NO2, SO2, H2S are measured). The analog signals are buffered and then measured with an ADS1115 analog-to-digital converter. This board also contains two temperature/humidity sensors, the SHT31 and the HDC1080, which are placed side-by-side for measurement comparison and redundancy. An additional circuit board with an SHT31 sensor and air intake slots is placed in the fan-aspirated (2510 fan) air intake column at the base of the device, to compare internal and external environmental conditions. These three boards were designed by Chris for the WeatherCube project. A solar panel, a battery, and a solar charging board are used for power management.
What were some of the challenges you faced?
It was challenging for us to do development at this scale. We’re set up in a garage-scale lab and had only previously done small orders with hand-assembled circuit boards and cases. Handling this project at scale, under budget, and within our time frame meant procuring tens of thousands of components from a dozen different vendors, coordinating timelines for multiple service providers, and building a contract labor team to handle final assembly and testing. There was definitely a learning curve, but we eventually got the hang of the logistics, and we’re on track to get the first batch of 250 WeatherCubes made and deployed this summer.
What is your hope for the communities you are serving?
We hope that this project can in the short term help residents understand local air quality levels, and use that to make decisions that can better their health. For example, if you have asthma and walk to work or the bus, is there a route you can take that reduces how much pollution you’re inhaling? Maybe there’s a park nearby that you didn’t think to go to which has lower pollution levels. Many Baltimoreans bike to work and would be happy to take a different route if it meant breathing in less pollution; hopefully in a few weeks to months we’ll have the information that can help me make that decision. In the long term, depending on the results, we hope that we can use this project to support sound policy decision making that helps make our city cleaner and healthier for all.
The team at Baltimore Open Air sounds excited, and they will soon have results as they deploy their monitors in September. This is all a nice connection to research first done by Anna for the Urban Heat Island Sensors project for the Office of Sustainability. As for the folks at Civic Works, creating jobs that lead to a green economy just makes sense. I’m giving a big shout out to the team—Anna Scott, Chris Kelley, Dr. Yan Azdou, Dr. Ramya Ambikapathi, Anne Draddy, Kristin Baja and John Ciekot. A big congrats to the new technicians and may Arduino always be in your favor!
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