In the fire safety strategy, compartmentation allows fire and smoke within defined areas, buying time for evacuation and emergency response. As building regulations evolve to ensure better and more effective compartmentation, designers must consider other attributes than fire resistance in passive fire protection solutions. One increasingly vital attribute is virtually airtightness, that has high relevance in several building codes for energy efficiency and is also part of Green Building requirements.

This article explores why air tightness is a critical aspect and the role that passive firestopping solutions play in having effective airtightness in buildings. 

Smoke and Fumes: The Invisible Threat

While flames are the most visible danger in an event of fire, it is the smoke and toxic fumes that often pose the greatest risk. Smoke can spread at speeds of 15 to 100 meters per minute, drastically reducing visibility and disorienting occupants. Studies show that two-thirds of fire-related fatalities are due to smoke inhalation, and more than half of victims are not in the room where the fire originated.

Airtight firestop systems play a vital role in preventing smoke propagation between compartments, helping to protect both lives and assets. Beyond human safety, smoke can create chaos on property. It often contains halogens like chlorine and bromine, which, when combined with moisture, form corrosive acids. These acids destroy sensitive equipment such as servers, medical devices, cables, pipes and other building services, even if the fire never reaches them.

Virtually airtightness is very important in mission critical facilities. Mission critical facilities are broadly defined as containing any operation that, if interrupted, will cause a negative impact on business activities. Mission critical facilities like data centers, laboratories and hospitals require airtight compartments to cater to needs like clean environments, energy efficiency and total cost of ownership.
 
Infection Control in Healthcare Facilities

In healthcare facilities, airtightness is crucial for infection control. Operating rooms use positive pressure to keep contaminated air out, while isolation rooms use negative pressure to stop germs from escaping. This helps protect patients and staff from airborne infections. Airtight spaces also improve comfort and save energy. Without proper sealing, air leaks through joints and gaps, making it harder to help maintain clean and safe environments in healthcare facilities.

FIG 1 Airborne bacteria transmission (hch:199481)

Gas Extinguishing Systems
In critical infrastructure, where water or foam could cause irreparable damage, gas extinguishing systems are often used to suppress fires by reducing oxygen levels below 15%. These systems use gases like carbon dioxide, nitrogen, or inert mixtures.
However, their effectiveness hinges on the integrity of the compartment. If penetrations and joints are not properly sealed, fire extinguishing gases can escape the compartment, reducing the effectiveness of the system.

Since passive firestop systems are part of the compartmentation, it is necessary to select the ones that have been airtight approved.


Controlling Odors and Hazardous Gases
Many human activities produce odors and hazardous gases as a result. Examples of these are activities in industrial compounds (fuel and oil vapors), swimming pools (Chlorine vapors), sewage treatment plants or even household kitchens. To prevent those odors and vapors leaving the area where they are generated and to avoid other areas receiving them, airtight compartments are a must.

How airtight testing works as per different standards
 
The airtightness test is done according to EN 1026 (air permeability test method). As per EN 1026, an airtight module is built on a wooden frame installed in a pressure chamber and subjected to positive and negative pressure steps up to a maximum test pressure difference of 600 Pa to quantify air leakage.

The test results are shown in cubic meters per hour per square meter (m³/h·m²), which helps compare how airtight different materials are. A lower number means better airtightness; less air is leaking through the material. If the number is high, it means more air is escaping, which shows poor sealing. So, the lower the value, the better the product is at keeping air and gases contained.

FIG 2 Logo on Hilti firestop products for airtightness

 
Hilti’s Solutions: Engineered for Airtight Compartmentation

Hilti is a global leader with more than 30 years of experience in passive fire protection. With the knowledge accumulated during this time and with their passion for innovation, Hilti can offer passive fire protection solutions that offer benefits beyond fire integrity. Some of those benefits are airtightness in many of their product portfolios like Hilti firestop sleeve for penetrations and Hilti acrylic sealant CFS-S ACR for sealing joint applications.

Hilti offers firestop products specifically recommended for supplementary sealing and refurbishment work, with proven airtightness validated through blower door tests.

Hilti helps bridge the gap between design and execution. It helps engineers and contractors move from specification to installation with code-compliant, optimized designs and efficient, safer jobsite practices. The approach reduces rework, improves sustainability, and ensures that what’s designed is actually built making construction faster, simpler, and more reliable and ensuring that airtightness is built into the project from the start.

Conclusion: Airtightness as a Strategic Advantage
 
Airtightness is no longer a secondary consideration, it is a critical aspect in modern construction that supports fire safety, infection control, energy efficiency, and environmental protection. By preventing the spread of smoke, gases, and airborne contaminants, airtight compartments help protect lives, preserve assets, and meet regulatory standards.

To maximize its benefits, airtightness should be treated as a design priority, not an afterthought in a project. This allows architects, specifiers, and engineers to select appropriate materials and systems, plan for proper sealing of penetrations and joints, and ensure compatibility with other building elements. Waiting until later stages can lead to costly rework and compromised performance.

References

• IFC Technical Library [firestop.org]
• https://www.fcia.org/Portals/0/FCIA%20ME%20Standards%202024v1-compressed.pdf
• https://insulation.org/io/articles/the-state-of-fire-resistance-compartmentation-and-firestop-systems/
• https://www.astm.org/e1827-11r17.html
• https://www.cibse.org/knowledge-research/knowledge-portal/tm23-testing-buildings-for-air-leakage-2022
• https://www.intertek.com/blog/2025/02-25-air-barriers-in-modern-construction/
• https://www.iea-ebc.org/Data/publications/2025-09-10-1725_Airtightness_Paper_Final.pdf
• https://cdn-web.iccsafe.org/wp-content/uploads/proclamations/TN02-Building-Tightness_pdf.pdf
• https://www.ashrae.org/file%20library/technical%20resources/covid-19/64-65_ieq_pantelic.pdf