Air Quality Sampler

Acknowledgements

Client: Erna Waterman, (EPA)

Project Advisor: Prof. Lisa Woodward (Mines)

Technical Advisors: Michael Hoppe (EPA), Michelle Kerr (EPA), Phillip Romig III (Mines)

Last Year’s Team: Andrew Clexton (Mines Alumni)

Video

Elevator Pitch

The Smeltertown Superfund cleanup operation was conducted between 1993 and 2003 by the EPA to address the soil and air contamination from past manufacturing operations on this property. The EPA and Colorado Department of Public Health and the Environment (CDPHE) inspect the Smeltertown Site every five years. In addition, air monitoring is important to local health departments to address concerns from their residents as poor air quality can cause serious health problems. 

The EPA has asked our multidiscipline Capstone Design@Mines team, Dust Busters, to design and test a new air quality sampler for PM_2.5 that can be easily transported across the country as a carry-on by plane for other sites of similar concern.  Our air quality sampler is unique as it uses a cyclone collection-based design with real time PM_2.5 data output, as well as a filter collection system so collected dust can be taken to a lab for further analysis. The air quality sampler also features a humidity sensor and temperature control carrying case to help the sampler operate in a broader range of climates.

Design Approach

(1) Air Quality Sampler

After discussing with stakeholders, the team has decided to take elements of existing air quality samplers in current use and make modifications to build an air quality sampler prototype. The air quality sampler (Picture 1) will rely on a cyclone design that will be used to collect air samples into a rotating filter holder that can store at least seven samples. In addition, there will be a PM2.5 sensor that will be able to collect data into a flash drive to analyze particulate density throughout the day. This design will also allow for minimal human interaction through the sampling period but will require setup and proper procedures in transporting samples to a lab for further analysis.

(2) Cyclone attached to pump.

The reason a cyclone (Picture 2) will be implemented is that it is an effective air current manipulator; it requires minimal maintenance; it has a low relative cost; it can operate at elevated temperatures; and it can handle liquid mist or dry materials. However, the cyclone has a low efficiency for smaller particulates, and the pressure drop must be considered. This was resolved through proper scaling of the cyclone in comparison to the size of the sampling box and the inflow rate required to transport dust particles into the filter collection system.

(3) Rotating Filter Holder

The design differs from current air quality samplers in that it will be able to store multiple samples using a rotating filter holder (Picture 3) and thus allow continuous sampling over a longer period. The rotating filter holder design may increase the size and weight of the sampler since integrating the moving parts adds complexity and will require more power. To address this, a long-lasting battery will need to be implemented. The battery must also be as light weight as possible since most of the weight comes from the power source.

(4) pms5003 PM2.5 Sensor

A PM2.5 sensor (Picture 4) will be included because it will provide information on the particulate sizes and particulate density through time of the site to analyze patterns and behaviors of the site. The sampler will be transported in a single weatherproof case that can be easily set up carried by an individual.

Design Solution

Our final design features a cyclone-pump collection system with a stock collection efficiency of 99.98%. These are connected by static plastic tubing so dust particles do not accumulate throughout the tubing. This tubing then runs through a PM2.5 sensor which is connected to an Arduino board that is producing live PM2.5 data accessible via USB. If the PM2.5 concentration exceeds a certain limit, the rotating filter rack is activated and turns to an unused filter. The rotating filter holder can hold up to 6 filters for sample collection. This leaves one slot on the rotating rack empty for when the sample is continuously monitoring. The stepper motors will remove the tubing while the rack rotates and reconnect when the next slot is in position. After a sample is taken, the rack will rotate back to the empty slot. The entire system runs on 72-Watt hour batteries that provided up to 5.5 hours of continuous power and can be recharged between sampling times and locations. 

To Summarize:

• Cyclone-Pump collection system
• PM2.5 Sensor
• USB module for data retrieval
• Stepper Motor Filter and Tube adapters
• Rotating Filter Holder Rack
  • Accommodates up to six samples and one slot for continuous flow
• 72-Watt hour capacity batteries
  • Rechargeable
  • 5.5-hour continuous power supply per battery 

Next Steps

Humidity Sensor running separately from rest of the sampler.

Our team was successful in testing each subsystem individually as well as collecting PM2.5 data while the cyclone, pump, and rotating filter operated. The PM2.5 data can be plotted against time to visualize PM2.5 concentrations. Better organization of the PM2.5 data is necessary for longer exposure times in the field. 

For future work, the client can decide how to integrate each component so the sampler can run autonomously for 20 hours at a time. Our group used Arduino for basic data results, but recommend exploring other interfaces to connect the sensors, pump, cyclone, filter rack rotations, and data output. If the client decides to push the project into a 3rd generation, we recommend having a computer science major on the next team to help with integrating the design code. 

The client can also look into testing different tubing materials and adapters to ensure no air flow is lost from the system so accurate calculations can be made. The air flow has to work in accordance with the cyclone and pump to ensure dust particles are not accidentally propelled too quickly or slowly into the filter collection rack. 

Since the sampler will be transported across the country, physical trials of the case and rotating collection system against turbulence or impacts should be tested for the sampler’s internal integrity. This includes drop testing, transportation, and potential water or humidity damage. The client can then look into writing a guidebook for EPA field agents to deploy, operate, and repair the sampler in the field based on common malfunctions throughout physical testing. 

Meet the Team