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. Additionally, 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. Additionally, 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
In the United States, to assess ageing resistance, Underwriters Laboratories (UL) specifies 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 UL standards. 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 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.