How Smoke Ventilation Systems Help in Fire Safety Compliance

Understanding Smoke Ventilation Needs

All buildings that are large, tall or have complicated layouts require smoke ventilation as part of an effective fire strategy. When a fire occurs, toxic smoke will begin filling the building from the point of ignition and rise through the structure. Without adequate means of controlling and removing this smoke, it can obstruct escape routes, hinder firefighting efforts and potentially increase the spread of fire.

Smoke ventilation systems provide these vital functions:

• Protecting escape routes and maintaining tenable conditions - Keeping stairwells, lobbies and corridors clear for evacuation.

• Allowing firefighting operations - Enabling firefighters to enter the building safely and locate the fire.

• Reducing fire and smoke spread - Limiting the upward and lateral movement of smoke.

The more occupants a building contains and the larger and more complex its design, the more robust its smoke ventilation provisions need to be. High-rises, atriums, large open-plan spaces and buildings with complex compartmentation all require deliberate engineering of smoke control.

Regulatory Requirements

In the UK, smoke ventilation is addressed through several key pieces of fire safety legislation and guidance:

• The Regulatory Reform (Fire Safety) Order 2005 - Requires facilities to have suitable measures for securing safe egress, including ventilation for smoke control.

• BS 9999 - The Code of Practice for Fire Safety in the Design, Management and Use of Buildings. Lays out technical smoke management solutions.

• The London Plan - For buildings in London, compliance with Part B of the London Plan is also required. This includes standards on smoke control design.

Together, these create a performance-based regulatory framework. In simple terms, facilities must have adequate means to control smoke movement such that tenable conditions are maintained along evacuation routes. Designs are assessed based on achieving these performance goals rather than rigid prescriptive requirements.

Common Smoke Ventilation Systems

There are a few primary types of mechanical smoke ventilation systems employed in buildings:

Natural Smoke Ventilation

Perhaps the simplest approach, natural ventilation involves permanently openable windows, louvres or other vents integrated into the building envelope. These allowstacking action and wind to vent hot smoke and gases. Effective for smaller buildings only.

Smoke Shafts

Vertical shafts or voids incorporated within the building structure and lined with material resistant to smoke and fire. Operated by automated or manual dampers, they channel smoke upwards and away during a fire. Commonly integrated into atrium designs.

Smoke Extract Fans

Mechanical fans installed at high level that can powerfully extract smoke through ductwork. Automatically activated by sensing technologies like smoke detectors or activated manually. Extensively used in large open spaces.

Pressurisation Systems

An alternative to extract fans, these use air handling units to positively pressurise stairs and escape routes, preventing smoke ingress. Effective for protecting long corridors and circulation areas.

The appropriate system or combination depends on factors like building size, layout, compartmentation and interaction with other safety systems like sprinklers. All are aimed at controlling smoke movement during the early vitally important stage of a fire's growth before firefighter intervention.

Case Study: A Large London Office Building

As a case study, consider a large open-plan office building with 20,000m2 of floorspace occupied across 20 floors in the City of London.

The design incorporates:

• Compartmentation into zones separated by 2-hour rated construction

• Smoke shafts located within the central atrium serving as collection points

• Smoke extract fans mounted atop the shafts rated for 10,000m3/min airflow

• Actuation by smoke detectors within each zone alarming the fans

• Interfaces with the BRE approved fire alarm and sprinkler systems

• Maintenance access hatches every 5 floors

• Commissioning tested zone isolation and fan extraction rates.

In the event of a fire, this would allow each floor to separately isolate, collect smoke via the shafts and powerfully remove it from the building - keeping stairs and lobbies tenable. It represents a well-considered mechanical smoke ventilation solution for a complex modern urban high-rise compliant with UK regulation.

Importance of Ongoing Servicing

While installation of quality smoke ventilation hardware is crucial, their continued reliable operation depends on diligent servicing and maintenance:

• Detectors require regular sensitivity testing and replacement after 10+ years.

• Dampers need monthly/annual exercising and lubricating.

• Fans must be load tested 6-monthly and given full overhauls yearly.

• Ducts and shafts need biannual inspections and cleaning if required.

• Spares should be kept on-site for immediate repairs or replacements.

Without this ongoing care, systems can fail to initiate or underperform during real fires due to degraded components. Building owners/managers must make adequate resource and contractor access provisions part of long-term compliance strategies. The upfront engineering counts for nothing without assuring continued serviceability.

Compliance Challenges

While smoke ventilation provides clear life and property safety advantages, keeping complex systems maintained to a high standard over many years poses compliance challenges:

• Legislative structures change - Systems installed to old codes may need updating.

• Access difficulties - Large rooftop plant can be hard to access safely for inspection/works.

• Budget limitations - Continuous servicing competes with other capital priorities.

• Lack of expertise - In-house staff may not fully grasp maintenance/testing requirements.

• Subcontractor quality - Reliance on external contractors introduces performance risks.

Proactive fire engineers can help building owners overcome these obstacles through strategies like:

• Long-term service contracts with vetted firms

• On-site spares and remote monitoring capabilities

• Comprehensive retrofit/upgrade plans

• Staff training programs

• Rigorous quality assurance of contracted works

With a cycle of continuous risk assessment, planned preventative maintenance and quality assurance processes - smoke ventilation effectiveness can be durably sustained for fire and life safety over the long run.

Conclusion

Mechanical smoke ventilation engineering has become a mainstream necessity for large, tall and complex modern buildings due to increasingly stringent performance-based fire codes. When properly designed, installed and maintained - these systems play a vital supporting role in buildings achieving fire safety compliance through effective control of toxic smoke movement during emergencies.

While upfront capital investment is required, the life safety dividends of functional smoke control in the form of protected evacuation routes and enabling firefighting significantly outweigh costs. Ongoing diligence from building managers is likewise important to ensure installed systems remain dependably serviceable well into the future. With a cycle of risk assessment, preventative maintenance and quality control - smoke ventilation is a highly effective smoke management strategy for compliance.