Passive fire protection: What is it and how does it work?

Introduction

Passive fire protection (PFP) is a fundamental pillar of fire safety engineering. Its main objective is to limit the impact of a fire, slowing its spread and protecting both people and structures.

Unlike active protection, which includes systems such as sprinklers or fire extinguishers, PFP does not require human intervention or mechanical activation to perform its function. Instead, it relies on building-integrated materials and designs that act as physical barriers against fire.

This article explores what passive fire protection is, how it works, what its main components are, and why it is essential in the design of safe buildings. It also includes key points that will serve as a technical reference for students and engineers specializing in fire safety.

What is passive fire protection?

Passive fire protection refers to a set of measures designed to contain a fire at its point of origin and minimize its effects. This is achieved through constructive elements that fulfill specific functions, such as:

• Fire resistance: Ensuring that structural materials can withstand high temperatures without collapsing for a defined period of time.
• Compartmentalization: Dividing a building into fire-resistant sectors to limit the spread of fire.
• Escape route protection: Ensure that escape routes remain usable during a fire.

PFP does not seek to extinguish the fire, but to provide critical time for people to evacuate safely and for emergency crews to act effectively.

How does passive fire protection work?

The operation of passive fire protection is based on two fundamental principles: fire resistance and compartmentalization. Both are supported by specialized materials and architectural design techniques.

Fire resistance

Structural elements (such as beams, columns and walls) must be able to maintain their integrity during a fire. This is achieved by:

• Fireproof coatings: Applications such as intumescent paints or mortars that protect structural steel from extreme heat.
• Fire-resistant concrete: Material that has an excellent capacity to withstand high temperatures without losing its mechanical properties.
• Fire resistant panels: Used in ceilings and walls to prevent premature collapse.

Compartmentalization

Compartmentation creates physical barriers that limit the spread of fire and smoke between different areas of the building. This includes:

• Firewalls: Designed to resist the passage of fire for a specified time (e.g., 60, 90 or 120 minutes).
• Fire seals: Materials that block openings in walls or floors (such as cable or pipe penetrations) to prevent fire or smoke from seeping in.
• Fire doors: Doors specially designed to resist high temperatures while maintaining their functionality.

Protection of escape routes

Escape routes must be kept free of smoke and heat for the time necessary to evacuate occupants. This is accomplished by:

• Pressurization systems in stairways.
• Use of fire resistant materials in corridors and exits.

Main components of the passive fire protection system

Fire-resistant materials

Materials used in PFP are designed to withstand high temperatures without losing their structural properties or contributing to fire spread. Examples include:

• Intumescent paints: They expand when exposed to heat, forming an insulating layer that protects structural elements.
• Fireproof mortars: Coatings applied on steel or concrete to increase their fire resistance.
• Fire-resistant composite panels: Used in enclosures and internal partitions.

Fire seals

They are essential for closing openings created by electrical, mechanical or hydraulic installations. These seals prevent fire and smoke from passing through compartmentalized barriers.

Fire doors

Made of materials resistant to extreme heat, these doors are designed to contain fire within a specific sector of the building while allowing safe evacuation.

Smoke barriers

Smoke is one of the biggest hazards during a fire. Smoke barriers prevent its spread through the building, improving visibility and reducing the risks associated with inhalation.

What are the essential elements of PFP?

Fire protection falls into two main categories: active and passive. Active fire protection systems, which are widely recognized, comprise fire detection and suppression devices. These include, among others:

1. Alarm systems for notification and evacuation of occupants.
2. Detection devices (smoke, flame, or heat detectors).
3. Automatic sprinkler systems for localized water discharge.
4. Alternative extinguishing systems (gas, foam, chemical agents) for scenarios where water is ineffective.

However, the synergistic implementation of both active and passive protection measures is crucial for the effective mitigation of human and material losses in fire events.

Passive fire protection, although less visible, plays a critical role in containing fires, preserving structural integrity, and facilitating safe evacuations when properly implemented and maintained.

The four critical areas of passive fire protection are:

1. Structural protection: Involves the application of fireproofing materials (cementitious products, mineral wool insulation, intumescent coatings) to structural elements such as steel and joint systems. Alternatively, the use of concrete in construction provides inherent fire resistance.
2. Compartmentalization: Consists of the implementation of barriers (fire partitions, smoke barriers) to confine fire to specific areas. Fire barriers, which include fire rated walls, floors and ceilings, are crucial to keep evacuation routes free of fire and smoke.
3. Opening protection: Comprises the installation of fire doors and windows in fire barrier openings. It also includes fire dampers in duct systems and smoke resistant curtains for effective smoke management and evacuation.
4. Fire stop materials: These are applied to limit the spread of fire in the event of penetration of fire barriers. These may include fire-retardant cable sheathing, joint systems and perimeter fire barriers.

The comprehensive implementation of these passive fire protection measures, in conjunction with active systems, is essential for a complete and effective fire safety strategy in buildings.

Know the key points as a fire safety strategy

Relevant regulations

Be familiar with international standards such as those established by the NFPA (National Fire Protection Association) or the European EN 1366 on fire resistance.

Be familiar with applicable local codes, such as the Technical Building Code (CTE) in Spain or NFPA 101 Standards in Latin America.

Fire resistance classification

Construction elements are classified according to their capacity to resist fire for a given time:

1. R (Resistance): Structural capacity against heat.
2. E (Airtightness): Prevent the passage of fire or hot gases.
3. I (Insulation): Maintain a safe temperature on the opposite side of the fire.

Testing and certification

Materials and systems must undergo standardized testing in accredited laboratories to ensure their effectiveness. Certifications such as UL (Underwriters Laboratories) or CE (European Conformity) are essential.

Integration with active protection

PFP should be complemented with active systems such as automatic sprinklers or smoke detectors to maximize fire safety.

Periodic maintenance

The effectiveness of passive systems depends on proper maintenance over time, ensuring that materials have not been damaged or deteriorated.

Technological innovations in passive fire protection

Technology is transforming the way we design and implement passive fire protection systems:

• BIM modeling (Building Information Modeling)

It allows simulating fire scenarios and optimizing the location of fire barriers from the early stages of architectural design.

• Research is developing new composite materials that are lighter, more durable and fire-resistant.
• Integrated IoT sensors.

Connected sensors can continuously monitor structural conditions and alert to potential failures before or during a fire.

The most effective materials and technologies in passive fire protection (PFP) are those that combine fire resistance, ease of application and the ability to limit the spread of fire and smoke. The key materials and technologies, based on current trends and recent advances, are listed below:

Most effective materials for passive fire protection

Intumescent paints

Function: These paints expand when exposed to high temperatures, forming an insulating layer that protects structural elements (such as steel and wood) from extreme heat.

Benefits: Delay structural collapse, are easy to apply and offer an aesthetic solution by integrating with the architectural design.

Fireproof mortars

Types: Rock wool mortar and vermiculite mortar.

Characteristics: Both materials are sprayed on structures to form a thermal barrier. Rock wool is known to withstand temperatures in excess of 1,000 °C, while vermiculite combines lightness with high thermal resistance.

Uses: Protection of beams, columns, and ceilings in industrial and commercial buildings.

Fire-resistant panels

Materials: Composite panels based on gypsum, silicates or mineral fibers.

Applications: Enclosures, internal partitions and wall claddings to ensure fire compartmentation.

Fire seals

Purpose: To block openings in walls or floors created by electrical, mechanical or hydraulic installations.

Advantage: They prevent the spread of fire and smoke between compartments by means of materials such as intumescent foams or fire-resistant mastics.

Rock wool

Characteristics: Its multidirectional fibrous structure provides excellent thermal and acoustic resistance.

Applications: Used as thermal insulation in facades, roofs, and fire walls.

Most effective technologies

1. BIM modeling (Building Information Modeling): Allows simulating fire scenarios from the early stages of architectural design, optimizing the location of fire barriers and passive protection systems.
2. Nanotechnology in fireproof materials: Recent advances have enabled the development of lighter, more flexible and heat-resistant materials through nanotechnology, improving their performance without increasing structural weight.
3. Integrated IoT sensors: Connected sensors continuously monitor structural conditions and warn of potential failures before or during a fire. This improves the system’s predictive capability.
4. Stair pressurization systems: Ensure evacuation routes remain smoke-free during a fire, improving safety for occupants.
5. Air-cell firewalls: Incorporate internal chambers that improve their thermal performance, increasing their ability to withstand high temperatures for extended periods of time.

Conclusions

Advances in materials such as intumescent paints, fire-retardant mortars and rock wool, along with technologies such as BIM and IoT, are redefining passive fire protection. These tools not only improve structural safety, but also facilitate regulatory compliance and reduce the risks associated with fires in modern buildings.

Passive fire protection is an essential tool for ensuring structural and human fire safety. Its effectiveness lies in the right combination of fire-resistant materials, strategic compartmentation and escape route protection. For students and specialized engineers, understanding the technical fundamentals, applicable regulations and recent innovations is key to designing safe buildings and meeting the highest standards.

Ultimately, passive fire protection not only saves lives, but also minimizes economic and environmental damage from fires, establishing itself as an indispensable investment in any modern architectural project.

References

1. https://www.epri.com
2. https://www.fireprotectiononline.co.uk/info/simple-how-intumescent-products-work/
3. https://www.linkedin.com/
4. https://extintorescontraincendios.com/blog/noticias/guia-completa-sobre-sistemas-de-proteccion-pasiva-contra-incendios