Drop Down Seals

The role of drop-down seals in passive fire protection

Under-door gaps are one of the most commonly overlooked weaknesses in a fire door assembly. Even a correctly specified FD30 or FD60 door can be compromised if smoke and hot gases can travel freely underneath it. Drop-down seals address this directly by:

• Maintaining fire compartmentation between rooms, corridors and stairwells
• Providing a smoke protection barrier that limits the spread of cold and hot smoke
• Preventing under-door leakage of flames, toxic gases and fine particulates such as dust
• Supporting the overall integrity of the passive fire protection system components that make up a compliant fire door set

Because they only engage when the door is closed, they do not interfere with day-to-day use, accessibility or flooring transitions — making them one of the most practical fire safety upgrades for both new-build and refurbishment projects in the construction industry.

Compliance and performance

Drop-down seals contribute to fire door compliance when specified and installed in line with the door manufacturer's tested configuration. Key performance considerations include:

• Fire resistance — seals used on fire-rated doors should be supported by test evidence to BS EN 1634-1 or BS 476: Part 22, matching the door's FD30, FD60 or higher rating.
• Smoke control classification — smoke leakage performance is typically assessed to BS EN 1634-3, with seals contributing to "Sa" (ambient smoke) and "S200" (medium-temperature smoke) classifications.
• Acoustic performance — by closing the under-door gap, drop-down seals can significantly improve a door's Rw (sound reduction) rating, which is why they are routinely specified in hotels, student accommodation, offices and healthcare environments.
• Threshold tolerance — most models accommodate a drop of 10–20mm, allowing for uneven floors and carpet transitions without compromising the seal.

Always check the fire door manufacturer's field of application to confirm that a specific drop-down seal is approved for use with the door in question.

Order with confidence

Enjoy next working day delivery on drop-down fire door seals when you order before 4pm. If you need help choosing the right seal for your door specification, fire rating or acoustic requirement, get in touch using the live chat feature or call us on 029 2085 7959.