How will the blended gas affect my gas appliances?

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  3. How will the blended gas affect my gas appliances?

The effect of blended gas on how appliances operate is one of the areas which are being assessed as part of HyDeploy.

This is because there are some differences in the way that hydrogen burns compared with natural gas. Although these differences are limited when hydrogen is used at a blend below 20%, it is important to understand and evaluate these factors in assessing the risk and determining the proposed blend.


Factors to assess:

  • The shape of the flame, which may change slightly. In general, this is not an issue, but it is important to ensure that any control systems on the appliance are not adversely affected by this.
  • The flame may sit slightly closer to the burner itself. Therefore, it is important to understand the impact this may have on the temperature of the components and the conditions under which they are designed to operate.
  • At high levels of hydrogen and under particular conditions it is possible for the flame to move back into the burner itself. This is a phenomenon called ‘light back’ which can cause the flame to go out. All appliances sold since 1996 have already been tested for this, using a hydrogen blend of 23%.
  • In order to protect users, a number of safety devices are used in gas appliances, for example to cut off the gas flow if the flame goes out. As part of the testing programme, these devices are being tested to ensure that they continue to operate properly with the hydrogen and natural gas blend.
  • If a fuel containing carbon does not burn properly, it has the potential to form carbon monoxide which is poisonous. Proper burning is controlled by managing the ratio of fuel and air in appliances. Although the addition of hydrogen to natural gas reduces the carbon content of the gas, it is important to ensure that it still burns properly.


HyDeploy’s own research will build on the work done internationally on hydrogen and natural gas blends. The laboratory testing programme and the safety checks on campus are all designed to assess these aspects. The evidence collected through this process will inform the level of blending proposed. Only if the HSE is satisfied will permission be granted to proceed to the live trial.

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