Research and analysis

Net zero: Hydrogen monitoring review: summary

Published 28 February 2025

Applies to England

1. Chief Scientist’s Group report summary

This project assessed the need for, and availability of, methods for monitoring molecular hydrogen in air. The Environment Agency and site operators can use this information to inform any monitoring needed at hydrogen production and storage locations, including stack and fugitive emissions, and leaks during repair and maintenance.

1.1 Background

It is widely expected that hydrogen use will form part of the pathway to net zero. However, it is known that hydrogen in air can extend the atmospheric lifetime of methane, a potent greenhouse gas. Therefore, it is important to monitor hydrogen leakage to ensure that it does not reduce the overall benefits of using hydrogen. To date, hydrogen monitoring has focused on the safety risk to workers and the public, but there is now a need to monitor and better understand the contributions that smaller-scale hydrogen leaks could make to atmospheric concentrations.

1.2 Approach

This project first reviewed the available scientific and grey literature on hydrogen emissions during production, transport and storage. The data monitoring requirements for a given emissions situation were then identified. A standard monitoring method requires: (1) a suitable instrument to measure hydrogen concentration, (2) a sampling strategy, (3) a means for converting hydrogen concentration to emission rate, (4) an agreed and established protocol and quality system, and (5) a way to validate method performance.

1.3 Results

This report summarises laboratory-based performance tests undertaken on seven different instruments that measure the concentration of hydrogen in air. Although the review identified instruments on the market that measure hydrogen concentrations, there were no complete methods available for monitoring emissions rates at sites. These instruments are designed only to measure the concentration of hydrogen during a snapshot in time. To be able to measure hydrogen emissions rates, rather than just concentrations, these instruments need to be included within complete methods. In future, technologies such as Raman spectroscopy remote sensing, distributed sampling, low-cost sensors and acoustic techniques may be able to provide greater coverage of the potential spatial and temporal scales of hydrogen emissions.

1.4 Conclusions

While instruments are available for monitoring hydrogen concentration, we are still some way from having a complete hydrogen monitoring method. Further development of both instrumentation and methods would then allow hydrogen leakage to be assessed more accurately. Exploratory monitoring at specific sites would provide valuable information on approaches to hydrogen monitoring.

1.5 Publication details

This summary relates to information from the following project:

• Report: SC230001/R                 
• Title: Net zero: Hydrogen monitoring review                                                                             
• Project manager: Helen Brooks, Chief Scientist’s Group                                                  
• Research Contractor: National Physical Laboratory

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency