Air Sealing

Air moves before fire becomes visible.

Air sealing is the control of unintended air pathways within a building. These pathways—formed by gaps, joints, penetrations, and construction tolerances—allow air, smoke, and heat to travel through the structure long before flames reach visible surfaces.

In fire conditions, these routes accelerate smoke spread, undermine compartmentation, and reduce the time available for safe escape.

Air sealing addresses what is often overlooked: the movement of air as a carrier of risk.

What Is Air Sealing in Construction

Air sealing involves closing and controlling gaps within the building envelope and internal construction to prevent uncontrolled air leakage.

These gaps occur at:

• Service penetrations

• Junctions between walls, floors, and ceilings

• Interfaces between different construction materials

• Around windows, doors, and structural elements

Air sealing is not a single product or trade. It is a continuous strategy that aligns with both energy performance and fire safety objectives.

Why Air Sealing Matters for Fire Safety

Smoke is the primary cause of fire-related fatalities.

Before temperatures rise to critical levels, smoke and hot gases move through available air paths. Unsealed gaps allow smoke to bypass compartment lines, spread rapidly through concealed spaces, and compromise escape routes.

Air sealing contributes to fire safety by:

• Restricting smoke migration

• Supporting compartmentation integrity

• Slowing the movement of hot gases

• Improving the performance of fire stopping systems

Fire protection depends not only on resisting flame, but on controlling movement.

Relationship Between Air Sealing and Fire Stopping

Air sealing and fire stopping are closely linked but serve distinct functions.

Fire stopping systems are designed to resist fire and maintain compartmentation at penetrations. Air sealing addresses the smaller, often unrecorded gaps that sit around and between these systems.

Without effective air sealing, even correctly installed fire stopping can be undermined by adjacent leakage paths. Together, they form a continuous barrier to both air and fire.

One addresses tested resistance. The other ensures continuity.

Where Air Leakage Commonly Occurs

Air leakage is typically found at interfaces rather than within primary construction elements.

Common locations include:

• Junctions between structural elements

• Service penetrations and service zones

• Ceiling voids and floor edges

• Around window and door frames

• Behind drylining and within concealed cavities

These areas are often concealed once construction is complete, making early identification and sealing essential.

Materials and Methods Used

Air sealing is achieved using a combination of materials selected for compatibility with the surrounding construction and fire strategy.

These may include sealants, gaskets, membranes, tapes, and fire-resisting products where required. The choice depends on the size of the gap, the movement expected within the joint, and whether fire resistance is also required.

Application must ensure full continuity, adhesion to substrates, and durability over time.

Installation Approach and Sequencing

Air sealing is most effective when integrated early into the construction process.

It requires coordination between trades to ensure that gaps are identified and addressed before they become inaccessible. Sequencing is critical, particularly where services pass through multiple layers of construction.

Late-stage sealing often leads to incomplete coverage and reliance on surface treatments rather than embedded solutions.

Air sealing is not a final fix. It is a planned layer of the build-up.

Quality Assurance and Verification

Air sealing performance must be verified.

Inspection typically includes visual checks, photographic records, and where required, airtightness testing to measure air permeability. Documentation records the locations sealed, materials used, and installation conditions.

This forms part of the wider compliance record, supporting both energy performance requirements and fire safety obligations under the Building Safety Act.

Integration with Passive Fire Protection Systems

Air sealing supports and enhances:

• Fire stopping at penetrations

• Cavity barriers within concealed spaces

• Fire-resisting walls and floors

• Fire doors and compartment lines

Together, these systems form a continuous defence against both fire and smoke movement.

Discontinuity in any layer creates a pathway.

Sectors and Applications

Air sealing is applied across:

• Residential and high-rise developments

• Commercial and office buildings

• Healthcare and education facilities

• Industrial and logistics environments

• Refurbishment and retrofit projects

Where airtightness and fire safety intersect, air sealing becomes essential.

Why Work with JW Simpkin Ltd

Air sealing is delivered as part of a wider strategy of controlled compartmentation.

JW Simpkin Ltd approaches air sealing with the same discipline applied to passive fire protection systems—ensuring continuity, compatibility, and full documentation. Work is coordinated with fire stopping and cavity barrier installations to remove gaps rather than conceal them.

The smallest opening often carries the greatest consequence.

For more information on Air Sealing or for a quote call us today on 01332 664700 or make an enquiry using the form below