f National Hydrogen Safety Assessment

Hydrogen is being proposed as a suitable low carbon alternative to natural gas. It has the potential to reduce green-house gas emissions across Great Britain’s industrial landscape but also for heating buildings. The Department of Energy Security and Net Zero (DESNZ) statistics show domestic heating currently accounts for 37% of the country’s CO2 emissions.
Hydrogen and natural gas are very similar when compared with other fuel sources. They are both gaseous at distribution operating pressures, they can both be burned to release energy, and they are both non-corrosives. This means that a piped distribution system and combustion appliances can be used to exploit their captured energy. They also differ from one another in that hydrogen has a broader range of flammability and lower ignition energy but is also much more buoyant and has higher diffusivity. Hydrogen does not have the potential to produce carbon monoxide when burnt, the Health & Safety Executive’s (HSEs) incident statistics suggest that by 2032 there will still be 1.5 fatalities per year attributed to carbon monoxide poisoning as a direct result of using methane based natural gas for heating and cooking.
A Clean Heat Policy Decision from the Government is due in 2025. Ahead of this, DESNZ has commissioned the Health and Safety Executive to carry out a Comprehensive Formal Assessment (CFA) of all safety and technical evidence on hydrogen, due in mid-2025. The National Hydrogen Safety Assessment (NHSA) is being submitted to HSE, along with other evidence, for assessment as part of the CFA.
The purpose of the NHSA is to describe the minimum general arrangements that will be required to demonstrate that a network and its connected properties can be converted to hydrogen and be operated safely, with risks appropriately managed for those working on the system or whose safety may be impacted, including the general public (section 3). The NHSA applies to the transmission, distribution and end use of hydrogen but does not include production or storage. At this time no specific parts of a network are planned for conversion and the NHSA therefore sets out the general approach to be taken for conversion and operation rather than detailed plans.
Subject to a successful policy decision on hydrogen for heating, supported by HSE’s Comprehensive Formal Assessment of safety evidence, the approach will be to develop detailed plans and safety cases to allow progression to delivering hydrogen conversion. The differences between natural gas and hydrogen mean that to transition from one gas to the other, with the intention of utilising the same piped distribution system and end-utilisation, requires due diligence, assessment, and where necessary, updates to the system, both to the assets themselves or the way they are operated.
This report was submitted to HSE for their assessment of the safety evidence for 100% hydrogen heating, which can be found at Hydrogen heating: HSE assessment of the safety evidence - GOV.UK.
Queries should be directed to DESNZ: https://www.gov.uk/guidance/contact-desnz.