# Toward Portable and Affordable Air Quality Monitoring: A 3D-Printed Platform for Colorimetric NO2 Quantification from Vehicles’ Exhaust Emissions

## TL;DR

A low-cost, 3D-printed device was developed to measure nitrogen dioxide emissions from vehicles, showing it can detect small amounts and differentiate between fuel types.

## Contribution

A portable, affordable platform using colorimetric detection and 3D printing for NO2 quantification in vehicle exhaust.

## Key findings

- The device achieved a detection limit of 0.6 ppbv and quantification limit of 2 ppbv for NO2.
- Diesel vehicles emitted significantly more NO2 compared to gasoline vehicles.
- The system is suitable for real-world air quality assessments and pollution source identification.

## Abstract

Air pollution from vehicular exhaust emissions remains
one of the main environmental and public health concerns in urban
areas. Nitrogen dioxide (NO2), a major component of combustion-related
pollutants, is of particular concern due to its harmful effects and
contribution to secondary atmospheric reactions. Its emissions from
engines are continuously monitored to mitigate pollution and to support
technological advances in vehicle energy sources. For this purpose,
suitable sensor technologies must be developed to enable in situ analysis
with ease of operation and compact design. This study presents the
development and validation of a portable analytical platform designed
for the quantification of gaseous NO2 directly from vehicle
exhaust emissions. The system was assembled using commercially available
components and 3D-printed parts, employing a colorimetric detection
method based on the Griess–Saltzman reaction combined with
an ESP32-S3 microcontroller responsible for data acquisition and signal
processing. Analytical parameters, such as sampling time and flow
rate, were optimized to improve the efficiency of the NO2 capture. The developed platform achieved a limit of detection of
0.6 ppbv and a limit of quantification of 2 ppbv for a sampling time
of 20 min, ensuring high sensitivity for trace-level detection. Application
of the device in real vehicle exhaust analysis revealed significant
variations among fuel types, with diesel vehicles exhibiting NO2 emissions substantially higher than those of gasoline-fueled
ones. The results demonstrate the feasibility of using low-cost, portable
systems for NO2 monitoring, supporting their potential
use in preliminary air quality assessments and urban pollution source
identification.