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Emerging Trends in Natural Smoke Ventilation on Building Façade
By: Nikhil Parasuraman
Fire and its repercussions on life are irreversible, monuments can still be rebuilt. Such unfortunate incidents and the fatalities forever prove to be scarring on the minds of those who have been through the gruesome ordeal and have lost their loved ones, or a part of themselves, irreversibly.
We can reduce the occurrence and increase the safety for an occupant by having strict guidelines like our National Building Code and Local Fire Laws that should be followed and audited yearly. We must also learn and adapt best practices from well-developed markets like Europe, the United Kingdom and the United States of America, and look for emerging trends which can help improve the life safety.
Around the world, buildings are getting taller due to the non-availability of land in prime locations of cities. They also bring an added uncertainty of limited ways to escape the burning inferno, during mishaps. Our idea should be to increase the amount of time the occupants have to escape the building safely and for the fire fighters to be able to fight that fire more effectively.
Below is one such way the United Kingdom deals with this issue—natural smoke ventilation in buildings to deal with this growing concern of fire safety in façade/ glazing buildings.
1. Regulations And Design Guide
The Construction Products Regulation (CPR) lays down harmonized rules for the marketing of construction products in the EU. The regulation provides a common technical language to assess the performance of products. It ensures the availability of reliable information in order that the performance of products from different manufacturers in the different countries can be compared.
The CPR represents a continued focus on the safety and other performance aspects of completed construction works and lays down aspects to consider for construction products. The seven ‘basic work requirements’ namely: mechanical resistance and stability; safety in case of fire; hygiene in health and environment; safety and accessibility in use; protection against noise; energy economy including heat retention and a new requirement – sustainable use of natural resources.
Building regulations are minimum standards for design, construction and alterations to virtually every building. They are developed by the government and approved by the Parliament.
Approved documents provide guidance on ways to meet the building regulations and contain practical examples plus solutions on how to achieve compliance and should be read in conjunction with the regulations to provide clarity.
Design guides offer additional assistance in achieving regulatory requirements. Often produced by professional trade groups or associations within specialist field.
2. The Principle Of “Smoke And Heat Exhaust Ventilation Systems”
To create a smoke-free layer above the floor by removing smoke and thus improving the condition for safe escape and permitting the fire to be fought in its early stages.
3. Product Regulation For Smoke Ventilation Systems EN12101
Part 1 Specification for smoke barriers
Part 2 Specification for natural smoke and heat exhaust ventilators
Part 3 Specification for powered smoke and heat exhaust ventilators
Part 4 Fire and smoke control installation of kits
Part 6 Pressure differential systems
Part 7 Smoke control ducts
Part 8 Smoke control dampers
Part 9 Control panels
Part 10 Power Supplies
4. Free Areas
4a. Geometric Free Area
The total unobstructed cross sectional area, measured in plane where the area is at a minimum and at right angles to the direction of air flow (as shown in the diagram below). Generally 1.0m2 geometric free area is required for head of stair, and 1.5m2 for end of corridor. However, each country and project will have its own requirement and is better to consult a smoke ventilation specialist.
Smaller area vents with more opening stroke will increase GFA compared to larger vents with smaller openings.
4b. Aerodynamic Free Area
The internal throat area (a x b) multiplied by the co-efficient of discharge (Cv) of the vent which is determined by the opening angle. This gives us the (Aa) Note: This information is only available if an aerodynamic test is carried out. Assumed coefficient values must not be used or transferred from one system to another. Generally 30-60 percent efficiency factors are achieved depending upon the opening angle.
5. General Principles Of Air Flow
The direction of airflow or smoke flow is an important factor when selecting a suitable vent type. Basic principles of airflow relative to external and internal temperatures and pressures will determine the optimum solution. As well as design guidance and best practice, regulations also dictate the hinge arrangements.
6. Applications Of Smoke Ventilation
6a. Non-residential application
Smoke ventilation by window automation in non-residential applications such as commercial, mixed-use, health and retail, utilise both vertical and inclined automated solutions. Such buildings in the UK are governed by BS9999 and product standard EN12101-2.
Unlike the free areas required for residential smoke ventilation, the size and design of the building will govern the vent type, orientation, free area requirements and method of area measurement. We also need to take into perspective – positive and negative loads such as snow, wind pressure when selecting right automation products. The hardware selection should be in accordance to and comply with the specifications laid out by the façade consultant.
6b. Residential application
Smoke ventilation by window automation in high occupancy dwellings, which are both private and public, e.g. hotels, apartments, student accommodation, etc.
Such buildings are governed by regulation Approved Doc B design guide BS9991 and product standard EN12101-2.
Automated smoke vents generally fall into two product groups namely staircase AOVs and end of corridor AOVs. (AOV – Automatic Opening Vents)
Free areas can vary depending on region and type of building and a smoke ventilation specialist should be able to help you with this.
6c. Minimum requirement when selecting natural smoke ventilation system
Actuators (Chain or Linear) must be 24v DC and tested to EN 12101 part 2.
A compatible control system with battery backup tested to EN 12101 part 10 for backup power when mains power failure is lost.
A Manual Override (MCP) switch, easily identifiable location and tested to EN 12101 part 9.
7. WHY NATURAL SMOKE VENTILATION
The issue with smoke
In a fire emergency, the smoke usually is the killer and not the fire itself. Smoke traps heat, reduces vision smoke ventilation naturally using AOVs. This early exhaust of smoke will not only help the occupants but also the fire officers coming into to fight the fire.
Where can we use SHEVs?
A few illustrations below show us the various applications where these principles can be put to use –
8. Steps to a Turn Key Ventilation System
These are generic guidelines based on country and type of building. System requirements vary and do consult a specialist in your region.
9. So, What Is The Take Away Here?
Bangalore International Airport, India
Safety of occupants during day to day operations and in an emergency play a vital role in having a successfully built infrastructure among other aspects. These days many if not all buildings are enveloped in glass and aluminium for its many benefits like light transmittance, lowering power consumption by day, providing great views of the surroundings and maintaining the internal ambient conditions.
When the glass façade is already doing so much, then why not make it more useful for its occupants by automating it for the release of smoke and toxic gases in the early stages of a fire. This is beneficial in many ways, the immediate reduction of toxic gasses and smoke levels, increased time to exit the building and improved visibility therefore reduces panic and overall reduces the risk factor for the occupants, fire fighters and the building itself.
Atria and Roof
Our latest NBC 2016 is not only paving the way to safer, secure and well engineered buildings but is the only building code to have a chapter in sustainability. The automatic venting system on glazing can not only be used for smoke ventilation but also for free cooling, night purge and natural ventilation. There by ‘creating a healthier and safer environment’.
Smoke control systems form a part of fire safety from building owners and adaptive natural ventilation and smoke control are often integrated into today’s modern buildings. Preventative maintenance of these systems is crucial to ensure that smoke ventilation takes place when required and to ensure people in the building have a safe passage of exit. Badly maintained systems are the responsibility of the building owners and prosecutions are on the increase. Newer systems are now becoming more intelligent and offer intelligent feedback of opening and closing operations so that equipment failures often caused by obstructions, can be identified and repaired at scheduled planned preventative maintenance visits, to ensure even higher levels of safety provision.
Director - India and SAARC Region
Nikhil ParasuRaman is the Director of India and the SAARC Region, SE Controls. Born in Mumbai, educated and raised in Chennai, he has a Bachelor’s Degree in Mechanical Engineer from Sri Venkateswara College of Engineering, Chennai. He has been serving customers with SE Controls India and the SAARC region since its inception in Indian market in 2012. He now leads a team in India that oversees designs for all the global offices and handles business development for his region. Over the past few years, he has come to be known for his technical knowledge in automatic smoke ventilation and control and his customer experience. He also happens to be a qualified commercial pilot from Melbourne, Australia and India, which he treats as a hobby alongside his passion for photography.