Are Ammonia Sensors Ready for Outdoor Use?

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Sensor Technology

Background:

• Ammonia (NH3) is a major agricultural air pollutant, necessitating accurate measurement near emission sources.
• Ammonia sensors offer potential for high-time resolution, cost-effective monitoring, but face metrological and technical hurdles.
• Sub-parts-per-million (sub-ppm) NH3 sensors for outdoor environments are emerging but require rigorous evaluation.

Purpose of the Study:

• To evaluate the field performance of six NH3 sensors against a reference instrument.
• To identify the metrological and technical challenges of using NH3 sensors in outdoor agricultural settings.
• To determine the readiness of current NH3 sensor technology for routine outdoor monitoring.

Main Methods:

• Field evaluation of five electrochemical and one chemiresistive-polymer NH3 sensor at a simulated poultry house emission site.
• Comparison of sensor data against a cavity ring-down instrument (Picarro G2103 NH3 analyzer).
• Assessment of sensor accuracy, precision, response time, and data capture under real-world conditions.

Main Results:

• Three sensors (TB600B, AM1 LC, AM2 HC) showed positive correlation with the reference analyzer, indicating potential for indicative NH3 measurements.
• The AM sensors exhibited very low data capture, suggesting potential improvements with longer operation.
• All tested sensors faced significant challenges in accuracy, precision, response time, and data traceability.

Conclusions:

• Current NH3 sensors have major technical limitations hindering their routine use for outdoor ammonia monitoring.
• The NH3 sensor industry and suppliers need to address identified technical challenges to improve sensor reliability and performance.
• Further development is required before outdoor ammonia sensor measurements can be considered ready for widespread application.