Grantee Research Project Results
Final Report: VOC Sensors for ppb-level Detection and Speciation
EPA Grant Number: SU840167Title: VOC Sensors for ppb-level Detection and Speciation
Investigators: Presto, Albert
Institution: Carnegie Mellon University
EPA Project Officer: Page, Angela
Phase: I
Project Period: December 1, 2020 through November 30, 2021
Project Amount: $25,000
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2020) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Air Quality
Objective:
The goal of this proposal is to develop a reliable and cost-effective VOC sensor suite for ambient and residential deployment with rough speciation, which will enable human exposure estimation and benefit pollution control. Five metal oxide semiconductor sensors, one electrochemical sensor, and two photoionization detectors will be combined as a sensor suite. Taking advantage of their different selectivity, numerical algorithms and machine learning algorithms will be established from laboratory and field calibration data to realize ppb-level detection and rough speciation. The developed sensor suites will be deployed indoors and outdoors to evaluate their performance. The purpose of this project is to reduce human exposure and VOC emissions, which is closely related to the P3 goals. Such portable and cost-effective personal devices will be useful tools to help people identify VOC emission sources and be aware of surrounded air pollution. This sensor suite will be especially beneficial to rural and disadvantaged communities who have limited access to public resources.The goal of this proposal is to develop a reliable and cost-effective VOC sensor suite for ambient and residential deployment with rough speciation, which will enable human exposure estimation and benefit pollution control. Five metal oxide semiconductor sensors, one electrochemical sensor, and two photoionization detectors will be combined as a sensor suite. Taking advantage of their different selectivity, numerical algorithms and machine learning algorithms will be established from laboratory and field calibration data to realize ppb-level detection and rough speciation. The developed sensor suites will be deployed indoors and outdoors to evaluate their performance. The purpose of this project is to reduce human exposure and VOC emissions, which is closely related to the P3 goals. Such portable and cost-effective personal devices will be useful tools to help people identify VOC emission sources and be aware of surrounded air pollution. This sensor suite will be especially beneficial to rural and disadvantaged communities who have limited access to public resources.
Summary/Accomplishments (Outputs/Outcomes):
This project aimed to test the ability of low-cost sensors to measure a suite of volatile organic compounds (VOCs) in ambient indoor and outdoor air. This project engaged a team of undergraduate students to lead sensor testing and eventual deployment.
Progress on our planned course of action was negatively impacted by the COVID-19 pandemic. During the Fall 2019 semester we assembled a team of undergraduates to participate in the project. However, these students were sent home, and our laboratories were closed, in March 2020. We were able to resume laboratory sensor evaluations in late 2020 and into 2021 but lost some of our initial momentum.
Overall, we demonstrated that low-cost sensors show promise as a way to monitor classes of VOCs in indoor and outdoor environments, though detection limits and cross-sensitivity continue to be a challenge.
Conclusions:
Multiple low-cost VOC sensors were mounted on a circuit board and tested under laboratory conditions. We focused on detection of two VOC benzene (as a proxy for all BTEX species) and formaldehyde. The sensor prototype is shown in Figure 1.
Figure 1. Sensor prototype. The sensors were mounted on a single circuit board. All data acquisition was handled via the LabJack. Sensors were tested under controlled conditions of temperature, RH, and VOC concentration.
Figure 2 shows the performance of one sensor (Figaro TGX 2602) when measuring benzene. There is reasonable correlation between sensor signal (in Volts) and benzene concentration. The sensors also showed a dependence on temperature and relative humidity. This means that deploying these sensors in real environments requires either co-located measurements of T and RH or that T and RH need to be actively controlled in order for the sensors to produce usable data. While Figure 2 shows results for one sensor type, other sensors showed similar behavior with T and RH interference.s: benzene (as a proxy for all BTEX species) and formaldehyde. The sensor prototype is shown in Figure 1.
Figure 2. Sensor performance at measuring benzene.
One major outcome of this project was the demonstration that low-cost sensors show promise for detecting VOCs like benzene and formaldehyde. However, since these sensors are also cross-sensitive to T and RH, as well as to other VOCs, more development is needed before they can be deployed in indoor or outdoor environments.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.