## 1 Introduction  
With rapid urbanization and advances in construction technology, the trend toward larger buildings has accelerated, increasing risks to human life during fires owing to more complex evacuation routes. In the 2017 Jecheon Sports Center fire, for example, a combination of factors--including blocked emergency exits, rapid smoke spread, and delayed evacuation--resulted in significant casualties. The incident revealed structural vulnerabilities, particularly the inadequacy of fire compartmentalization and evacuation safety [1]. Such incidents highlight the critical importance of establishing effective fire compartments and properly implementing their key components, such as firestop systems, to prevent fire from spreading and minimize risks to life and property.  
Fire compartments rely on fire-resistant structural elements and components, such as fire doors and shutters at openings. Equally crucial are firestop systems, which fill gaps around service penetrations and play a vital role in maintaining compartment integrity [2, 3, 4, 5]. Modern buildings contain various utilities, such as plumbing, electrical, and telecommunication systems that penetrate walls and floors, creating potential pathwaysfor fire to spread. To mitigate this risk, various firestop systems are installed at these penetrations [6,7].  
In South Korea, a firestop system approval regime was introduced in 2022 to prevent fire spreading through compartment penetrations. Firestop systems comprise diverse materials and installation methods, such as intumescent wraps and sealing compounds, and research on their performance is actively ongoing [8, 9, 10, 11, 12]. However, most existing studies focus on material properties, component geometries, or installation techniques. There remains a lack of quantitative experimental data directly applicable to improving the approval system, such as the relationship between firestop material volume and penetration size variations [13, 14, 15, 16].  
A critical issue in current systems is that even when the size of openings or penetrants is reduced, the same quantity of firestop material specified in prior approvals must still be applied. This often results in excessive application that does not reflect on-site conditions and creates inefficiencies, as separate approvals are required for each configuration. Meanwhile, several advanced countries have adopted flexible, performance-based certification frameworks--such as those based on ASTM E814 [17] and UL 1479 [18]--which allow for variable firestop specifications depending on penetration size and type. The uniform criteria in Korea, even under varying field conditions, incur unnecessary costs and promote inefficient construction practices [19]. Therefore, there is a pressing need to transition toward a performance-based, evidence-supported standard that reflects practical on-site conditions.  
In this study, the fire-resistance performance of firestop systems in metallic and non-metallic pipe penetrations is experimentally investigated by adjusting firestop material volume in accordance with changes in opening size and penetrant diameter. By comparing conventional conditions with situations in which the firestop material volume was incrementally reduced based on cross-sectional area, the potential for more flexible firestop design is explored and performance differences identified by penetration type. The findings aim to provide technical and empirical data to support improvements to Korea's firestop approval system.