Keeping Fire Safety Safe: The Role of Pressure Relief Devices


    Fire safety has always been critical in residential, commercial, and industrial settings. Among the various tools designed to combat fires, fire extinguishers are one of the most effective solutions. Storing an extinguishant in a pressurised vessel, which is portable and practical, enables first responders to control and extinguish a fire in its early stages.

    Due to the pressurised nature of fire extinguishers, incorporating a Pressure Relief Device (PRD) is essential for safety. We'll look at the history of PRDs, explain how they work, and go over the current legislation governing their use across the UK and Ireland.

    The History of Pressure Relief Devices

    The concept of pressure relief in fire extinguishers dates to early developments in fire suppression technology. Early fire extinguishers were basic and lacked features for user safety, unlike modern devices. Additionally, as technology advanced, so did fire extinguisher construction, meaning that the pressurisation levels increased. This made the need for a safety mechanism to prevent accidents caused by over-pressurisation even more important.

    In 1999, the UK government introduced the Pressure Equipment Regulations, following the introduction of a similar directive in the EU in 1997. The government designed this legislation to improve the safety and reliability of pressure equipment, including fire extinguishers, across the UK. The regulations mandated that there should be provision for safety devices such as PRDs to prevent potential explosions or other hazards, and for fire extinguishers, it focused on carbon dioxide extinguishers, as these operate at a higher pressure than other types of extinguishers.

    The introduction of PRDs was a significant milestone in fire extinguisher design. Initially, these devices were simple and often unreliable. Over the years, advancements in engineering and materials science have led to the development of more sophisticated and reliable PRDs.

    How Pressure Relief Devices Work

    Pressure Relief Devices maintain the integrity of fire extinguishers by preventing over-pressurisation caused by high temperatures or physical damage.

    Today's extinguishers commonly have one of two types of pressure relief devices:

    Burst Discs:

    One common type of PRD is the burst disc. This is a thin metal diaphragm that ruptures at a predetermined pressure. When the pressure inside the extinguisher exceeds this threshold, the disc bursts off, allowing the pressurised gas to escape and reducing the pressure inside the extinguisher. Burst discs are often seen on high-pressure extinguishers, such as CO2 extinguishers.

    Pressure Relief Valves:

    A pressure relief valve is spring-loaded. When the internal pressure reaches a certain level, this pushes the spring back and opens the valve to let excess pressure escape. Once the pressure decreases to a safe level, the spring forces the valve to close again, keeping the extinguisher operational. If over-pressurisation occurs with no one around, the extinguisher retains a safe amount of pressure and can be used in a future fire situation.

    All pressure relief devices are designed to activate automatically. This is crucial because it ensures that the extinguisher can respond to changes in pressure without the need for human intervention, which provides users with a critical safety margin.

    Current Legislation on Pressure Relief Devices

    Legislation governing life safety devices such as fire safety equipment is crucial to ensuring public safety. In the UK and Ireland, there are distinct differences regarding the use of PRDs with fire extinguishers.

    In the UK, the primary standard for fire extinguishers is BS EN 3-7:2004+A1:2007, supported by the Pressure Equipment (Safety) Regulations 2016. These standards mandate that only CO2 fire extinguishers are required to have PRDs. The rationale behind this requirement is due to the high-pressure nature of CO2 extinguishers. When compared to other types of extinguishers, such as water, foam, and powder, CO2 extinguishers operate at higher pressures and are therefore more susceptible to the risks of over-pressurisation.

    Ireland, however, takes a more stringent approach, following the tragic loss of life from an extinguisher exploding during a fire in Ireland in 1997. According to IS 291:2015+A1:2022, all portable fire extinguishers, regardless of type, must be equipped with PRDs. This standard aims to enhance safety across all environments, acknowledging that while the risk of over-pressurisation might be lower in non-CO2 extinguishers, it is still a life-threatening risk.

    Compliance vs Best Practice

    Compliance with these regulations is not just a legal requirement but a critical aspect of ensuring safety. However, there is also a moral question about what the best practice is for any fire extinguishers. By the nature of what they are, fire extinguishers are likely to be in proximity to high temperatures, which is the leading cause of over-pressurisation. And without a pressure relief device, there’s always a risk of the fire extinguisher exploding in the most critical situation.

    At Firechief®, all our main extinguishers carry pressure relief devices, because we’re on a mission to make the world a safer place. For us, that means producing quality, reliable fire safety equipment that can be relied on when the heat is on.


    The Firechief® range includes high-performance fire extinguishers, fire blankets, first aid kits, lithium-ion fire extinguishers and the Kitchen Stove Guard. For more information, call us on +44 (0)330 999 0019 or email

    The information contained within this blog is provided solely for general informational and educational purposes and is not intended as a substitute for professional advice. Before taking any actions based upon this information, we advise the reader to consult any and all relevant statutory or regulatory guidance and where felt necessary to consult a qualified fire or industry regulation professional. The use or reliance on any information contained herein is solely at the reader's risk.