Passive fire protection systems are essential in modern construction, serving to contain fire and prevent its spread through compartmentalization. While fire resistance is their primary function, the durability and ageing resistance of these systems are equally critical for ensuring long-term safety and performance. As buildings age, materials are subjected to various environmental stressors, making it vital for firestop products to retain their protective properties over time to maintain compliance and structural integrity.

Understanding Ageing Resistance in Firestop Systems

Ageing resistance refers to a product’s ability to maintain its functional properties despite prolonged exposure to environmental conditions such as heat, moisture, chemicals, and mechanical stress. For firestop systems, this means preserving fire resistance, elasticity, adhesion, and other essential attributes throughout their intended working life.

Key Components Influencing Ageing Resistance of Firestop Systems

The effectiveness of ageing resistance in firestop systems is determined by several key components.

• The polymer matrix, acting as the binding agent, forms the structural backbone and holds the firestopping additives in place. Commonly used materials like silicones, acrylates, and polyurethane foams have demonstrated long-term stability through historical data and testing.
• Firestopping additives, whether ablative or intumescent, are designed to react to fire by forming a protective crust or expanding to seal gaps. However, their performance can diminish over time due to environmental exposure.
• Ancillary components such as pigments, stabilizers, and plasticizers also play a role, as their migration or leaching can affect the flexibility and overall performance of the product.
• Metal components such as zinc can influence ageing resistance. While zinc offers corrosion protection, the thickness and quality of its layer are critical, thinner or cheaper coatings may degrade faster, especially in outdoor applications, where a thicker zinc layer is recommended to ensure long-term durability.

Environmental Stressors and Failure Modes of Firestop Systems

Firestop products face a variety of environmental stressors that can compromise their longevity.

• Thermal fluctuations, including heat and cold, can lead to softening, embrittlement, or fractures - especially when combined with mechanical stress from building movement or vibration.
• Moisture exposure can result in leaching components and promote microbial growth, including mold and mildew, which further degrade polymer chains.
• Ultraviolet radiation and chemical exposure from cleaning agents or industrial substances can accelerate material breakdown.

These stressors vary by application, underscoring the importance of evaluating firestop systems under realistic and representative conditions.

Testing Procedures and Standards to Assess Ageing Resistance

To assess ageing resistance, ETA procedures based on Technical Report TR024 require firestop products to undergo rigorous environmental conditioning. This includes 40 days of heat exposure at, for example, 80°C with 50% relative humidity, 28-day cycles of alternating dry and damp conditions, and 21-day condensation tests. Additionally, chemical compatibility with paints, solvents, and oils must be verified. In the United States, Underwriters Laboratories (UL) specifies similar procedures under UL 1479 (only for intumescent products), such as 180 days at 35°C with 97% humidity and 270 days at 70°C, followed by fire testing to evaluate expansion and pressure.

Hilti’s Approach to Ageing Resistance

Hilti supplements these regulatory tests with additional internal simulations to further validate product durability. These include procedures based on DAfStB (Deutscher Ausschuss für Stahlbeton) guidelines, originally developed for concrete durability, where firestop modules undergo 20 cycles of water immersion and temperature variation before fire testing. These internal tests are designed to reflect more aggressive or variable real-world conditions and complement the ageing protocols defined in ETA and UL standards.
Since TR024 alone may not provide sufficient basis for such decisions, Hilti’s internal testing offers a more critical and robust foundation for evaluating long-term performance. Hilti does not claim or guarantee any specific duration, as environmental factors in actual applications can be abrupt and unpredictable, potentially influencing product performance in ways that cannot be fully anticipated or controlled.
Hilti firestop products with ageing-resistant properties retain their functional attributes over time, making them especially beneficial for use across diverse segments where long-term reliability and environmental exposure are critical
Hilti recommends that firestop systems be included in routine building maintenance activities to help ensure continued performance and compliance, they should not be overlooked or set aside during inspections or repairs by building owners, facility managers or contractors.

Conclusion

Hilti’s comprehensive testing approach provides valuable insights into product longevity and performance. Although full ageing resistance cannot be guaranteed due to uncontrollable variables and material limitations, rigorous testing and realistic claims help ensure that firestop systems remain reliable and effective throughout their working life. As buildings evolve to meet higher standards of safety, sustainability, and comfort, ageing resistance will remain a key consideration in selecting and maintaining passive fire protection products.

For further enquiry or clarifications, please feel free to reach out to us at my.engineering@hilti.com