When it comes to fire safety, passive protection often does the quietest but most important job. It’s all about containing fire and smoke at the source—slowing the spread, protecting escape routes, and giving firefighters more time to respond.

If you’ve ever needed to run new cables or pipes through a fire-rated wall or floor, you’ll know it’s not as simple as just making a hole and patching it up. Every gap compromises your building’s compartmentation—and without the right solution, that could mean the difference between containing a fire and letting it spread.

That’s where intumescent fire pillows come in. These clever little blocks of protection offer a flexible, mess-free, and fully compliant way to seal service penetrations - especially in places where access is needed again later. Whether you’re working on a new build or updating an existing space, fire pillows make staying compliant that bit easier.

What Are Intumescent Fire Pillows?

Intumescent fire pillows are small, flexible blocks designed to seal gaps in walls and floors where services like cables, conduits, or pipes pass through. They’re filled with intumescent material - meaning it expands rapidly when exposed to high temperatures - and are usually wrapped in a durable, fire-resistant fabric casing.

In the event of a fire, the heat causes the material inside the pillow to swell and form a dense, insulating barrier. This expansion helps block smoke, flames, and heat from travelling through the penetration, maintaining the fire compartmentation of the building.

Fire pillows come in a range of sizes to suit different voids, typically including small (200mm x 130mm), medium (250mm x 150mm), and large (330mm x 180mm) options. You’ll also find foil-backed variants for added moisture resistance, and standard fabric versions for general internal use.

They’re often chosen for projects where access is needed later - making them a great alternative to sealants or collars in service areas that are regularly updated or reconfigured.

How Do They Work?

Intumescent fire pillows might look simple, but when a fire breaks out, they react quickly—and cleverly.

Here’s how they work, step by step:

1. Normal conditions - The pillows sit loosely within a wall or floor opening around cables or pipes. They’re not fixed in place, which means they can be easily removed and replaced when services change.
2. Fire breaks out - As temperatures rise, the intumescent material inside the pillow begins to expand.
3. Expansion – The material swells many times its original size, filling the gap around the services and tightly sealing the opening.
4. Compartmentation maintained – The expanded pillow acts as a fire and smoke barrier, helping to contain the fire within the compartment it started in. This buys valuable time for evacuation and firefighting.

This reactive expansion is what makes fire pillows so effective. They work passively—no need for power, sensors, or intervention—and only spring into action when they’re needed most.

Compared to other fire-stopping products:

• Sealants are great for permanent fixes, but once applied, they’re hard to remove without damaging the area.
• Fire collars are ideal for plastic pipes that melt away in a fire, but they’re not suitable for flexible services like cables or fibre.
• Fire pillows, on the other hand, offer a reusable, clean, and non-invasive solution - perfect for environments where services are likely to change or be upgraded.

They’re a versatile part of the passive fire protection toolkit, especially useful in data centres, riser cupboards, and commercial buildings where access to services is a regular requirement.

Are They Compliant with UK Fire Safety Regulations?

Yes, when you choose certified products, intumescent fire pillows are fully compliant with UK fire safety regulations. As with any fire-stopping solution, it’s vital that the products used meet the correct standards and are installed properly to ensure they perform as expected in a fire.

Relevant Fire Safety Standards

Fire pillows are tested to BS 476 Part 20 and EN 1366-3, which assess their ability to maintain the integrity and insulation of fire-rated walls and floors where services pass through. These tests simulate real fire conditions to ensure the pillows expand effectively and help maintain compartmentation for up to 4 hours, depending on the product.

Approved Document B Compliance

UK Building Regulations require that buildings are divided into fire-resistant compartments to slow the spread of fire. Approved Document B outlines how to achieve this, including the need to seal service penetrations with suitable materials. Intumescent fire pillows, when installed correctly, meet the guidance laid out in this document—helping building owners and contractors remain compliant.

The Importance of Certification

To ensure fire pillows perform as expected, always choose products that carry CE or UKCA markings and have undergone third-party testing by recognised certification bodies such as Warringtonfire, UL, or BRE. This gives you confidence that the product has been rigorously tested and approved for use in life safety applications.

Cutting corners with uncertified or non-compliant products could leave you exposed to serious risks - not just from a safety perspective, but legally and financially too. Fire protection is not the place to gamble.

Key Benefits of Fire Pillows

Whether you’re working on a new installation or need to make changes to an existing one, fire pillows offer a practical, low-maintenance way to stay compliant. Here’s why they’re such a popular choice:

• Easy to install and remove – No special tools or adhesives required. Simply slot them into place around cables or pipes.
• No mess, no curing time – Unlike fire sealants, there’s no waiting around or cleaning up. It’s a dry-fit solution you can get on with straight away.
• Reusable and adjustable – Need to reroute services later? Just remove the pillows and reinstall once you’re done - ideal for riser cupboards or comms rooms.
• Maintains fire compartmentation – Expands in a fire to seal off gaps and stop fire and smoke from spreading between rooms or floors.
• Works for temporary or permanent fixes – Whether you’re patching a void for a short-term job or sealing a long-term installation, fire pillows are a versatile option.

Fire pillows make it easy to meet fire safety requirements without slowing down your work or compromising on standards.

Are Fire Pillows Right for Your Project?

Fire pillows are a great fit for many scenarios, especially where flexibility is key. If you’re working in an environment where services may need to be upgraded or accessed regularly - like data centres, plant rooms, or riser cupboards - they’re a smart choice. They’re also ideal for retrofit projects, or temporary installations that still need to meet fire safety standards.

However, they’re not always the best solution for every situation. For permanent, fully sealed installations - particularly where movement or tampering isn’t expected - intumescent sealants, fire batts, or collars may offer a more robust, long-term fix. The key is choosing the right product for the job, based on the type of service penetration, the fire rating required, and how the space will be used.

If your layout is complex, or you’re unsure which solution fits best, it’s always worth speaking to a fire safety professional. Not sure what you need? Get in touch with our team - we’re happy to help.

Installation Tips and Best Practices

To get the most out of intumescent fire pillows—and ensure they perform when it matters—correct installation is key. While they’re designed to be simple to use, there are still a few important best practices to keep in mind:

• Ensure a snug fit: Fire pillows should be packed tightly into the opening, leaving no visible gaps around the edges or between the pillows. A loose fit could compromise the fire rating of the barrier.
• Never substitute with non-certified alternatives: Only use fire pillows that have been third-party tested and certified. Household materials or makeshift alternatives won’t provide the protection required—and could invalidate your fire strategy.
• Follow the manufacturer’s guidance: Each fire pillow may have slightly different installation instructions, especially if being used in conjunction with other fire-stopping products. Always refer to the data sheets and test evidence.
• Consider additional sealing if needed: In some situations, fire pillows may be used alongside fire-resistant mastic or boards to seal the perimeter and achieve the required fire rating. This is especially important in larger openings or mixed-service penetrations.

By following these steps, you’ll help maintain effective compartmentation and stay compliant with UK fire safety regulations while giving building occupants the best possible protection.