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Performance-based and prescriptive based fire design should be ensured  

Published : Thursday, 16 May, 2019 at 12:00 AM  Count : 139
Munaz Ahmed Noor

Munaz Ahmed Noor

Munaz Ahmed Noor

Fire is a tetrahedron- heat, oxygen; fuel and chain reaction among these three ignite fire. But sparks could not make fire if the oxygen level of air remains under 16 percent. Fire is a part of our nature and exists everywhere around us. So, fire can easily originate everywhere with the chain reaction of heat, Oxygen and fuel. We, the engineers, use codes while constructing buildings keeping fire incidents in mind. These codes are the minimum requirement in building construction. We call it prescription based code. But in Bangladesh, around 93 percent of buildings do not maintain the minimum requirement of prescription based codes.

Recently, our administration has moved up after the massive fire at Churihatta in Old Dhaka and Banani FR Tower fire. RAJUK has already started drives against the buildings which were not constructed maintaining the minimum requirement of prescription based code. According to RAJUK sources, there are 25 lakh buildings under their purview. Among them, around 21, 50, 00 are six-story building, and 88 thousand buildings are ranged seven-story to twenty-five-story. According to the RAJUK statements, now there is no scope of backtracking. A total of 24 RAJUK delegate visits field every day to collect information on all kind of irregularities. They hoped that they will take steps after getting full reports. No one should be spared after committing irregularities in construction of buildings.

Now, the point comes is that what will be the 93 percent of buildings that could not follow the minimum prescription -based code. Will the buildings be demolished? If these 93 percent buildings were demolished, what would be the losses? On the other hand, following prescription-based code in construction of the buildings does not guarantee 100 percent fire security. Many things also depend on building dwellers. How they are using the instruments suggested in prescription -based code is also very important. So, the world is now considering coming out of prescription -based code gradually. Now, they are thinking to shift performance based design to prescription -based design.

What is performance based design?

Performance-based design is a strategy where some goals are set to accomplish, which does not depend on the base of prescription. This idea can be applied in the construction of new buildings as well as in the code non-compliant old buildings. Setting some goals for the people who are abiding in these two types of buildings is called performance based design.

What is the difference between prescription-based design and performance-based design?

The first and foremost difference between these two types of design is prescription -based design only says a method; it does not asses any fire risk of the building. It does not observe whether the building is on high risk or low. But, the performance based design asses the risks and suggests actions accordingly. Secondly, prescription -based design is only applicable to the general buildings. Where performance based fire design can be applicable for both generic and non-generic buildings.

What are the goals of performance-based fire design?

Some goals should be kept in mind in assessing performance-based fire design. The goals are life safety, environment, building operation, security, risk assessment, risk analysis, workplace safety, content, smoke control, mission protection and identify the floors which are under fire-risk.

How can I set performance-based fire design?

Fire incidents can be classified in three stages- pre flashover, flashover and post flashover. In pre flash stage- both life and wealth can be saved easily. But, in flashover and post flashover stage- it becomes very tough to save the people inside the building. So, what should be done must be done in the pre-flash stage. If we look into the fire incidents occurred all over the world, we see that most damage and calamity caused when the fire could not be distinguished in the pre-flash stage.

On the other hand, when the fire could be extinguished in the pre-flashover stage, no damage occurred. The fire remains in pre flash over stage for very shortest period of time 3-5 minutes. But, the problem is fire brigades could not reach with in this shortest period of time. Fire shifts to flashover stage from pre flashover stage. Then it would become impossible for the fire fighters to save life and wealth. When fire stays in flashover and over stage, fire brigades try to decelerate the speed of fire, they try to stop the extension of fire and try to manage smokes. That is the task for them in those two levels. They have nothing else to do.

It should be kept in mind that the people in intimate contact of fire are very tough to save in performance based fire design. Except them, all other people can be saved. Then, it comes to the safety of wealth. In this case, first of all, it should be ascertained that the contents remaining inside the building carry how much value. Because, if the affected building is considered as archaeological heritage, there might be many artefacts' those can be considered more valuable than everything. If that artefacts damage, history can be lost.  

Then it comes to the issue of the building's mission protection, companies like Google, Yahoo and Facebook never want to stop their service for a single minute. So, it also can be considered as a goal. Next comes to smoke management. How much space do you let to extend smoke? Around 70 percent of people killed due to smoke.
To save from smoke, we must try to distinguish the fire in its pre flashover stage which exists only 3-5 minutes. In this situation the victims must try to step down to the ground since, smoke always tends to go up. Here, I can put the example of the massive fire of the hotel MGM Grand Large at Nevada City in California in 1980. That incendiary claimed 85 lives and 650 were injured.

The hotel housed more than five thousands of people during the fire. The hotel was a 26-story building. Fire originated at the ground floor. Around 15-20 people those were in intimate contact of the fire all killed. They were trapped at the ground floor and could not come out. They were asked to stay at their respective rooms instead of fidgeting in panic. The people who followed the direction and stayed in their respective rooms remained unscathed. But the people residing in 14-24 floors who tried to step up were killed in smoke.   

But, if they could reach to the roof, the chances of escaping would go up. The same thing happened at Banani FR Tower. I noticed that a media report wrote, a woman was trying to stair up to the roof from 14th floor. She was asked to go to the roof. Allah knows what would have happened if she remained at the 14th floor. But she could not survive after going up to 21st floor as she could not reach to the rooftop. After reaching 21st floor, she was choked to death due to smoke.

So, this is also a vital point. After that a risk analysis assessment should be prepared on how much fire threat the building is carrying. Such as- it was suggested to keep 5 feet wide stairs in the prescription- based code. But the stairs are only 3 feet wide. Then what will we do? Will we demolish the building? Though, the three feet wide stair will slow down the evacuation rate, people will be able to come out if stairwell pressurisation is enforced.
The buildings those are in code non-compliant stage should be tried to bring them under performance goal stage.  If that is not possible then occupancy and content should be removed. For example- If there are 1,000 people in a building but advice comes to keep 700 after conducting performance analysis, then it must be done considering life safety. Then, it can be found out through risk analysis that which floors are more vulnerable to fire. Then the task is to develop a system to confine fire smoke to the floor so that the smoke could not extend to other floors. This can also be a performance goal.

In spite of all these initiatives, the authorities concerned in each building must keep a designated fire marshal. The building owners must keep a sub fire marshal in each commercial building too. The fire marshal will be designated to douse fire at pre-flash stage as he is expert at it. Everything within the building will be at his or her finger's tips. If he or she has no proper knowledge of everything during a fire incident, there will be no benefit rushing randomly.

If there is enough fuel, fire takes 3 to 5 munities to spread. If there is not, fire will douse itself. So he will get 5 munities in his hand to take appropriate action.  The first and foremost duty of the fire marshal will be to inform each person of the building about the fire incident and direct them what to do in this case. He will arrange fire drill at regular basis so that residents of the building get used to safeguard themselves from fire in their own.
At present, Fire fighting is no more confined to the professionals like civil engineers, architects, mechanical engineers or electrical engineers. There happened a paradigmatic shift in this field across the world. Subjects like Fire Protection Engineering, Bachelor of Science in Fire Protection Engineering, are in run in different universities of the developed countries of the world.

The universities of our country can also introduce this subject as their institutional capacity has been improved in recent years. Today or tomorrow, they have to open course on this topic. Then, why not today? The 'will be' graduates in Fire Protection Engineering might play a vital role in fire fighting. They might safeguard lives and properties of people utilizing the tools and techniques of modern science and technology.

Bangladesh has already fulfilled the eligibility criteria set by the United Nations (UNO) to be recognized as a developing country, crossing over from the list of least developed countries (LDC). Our country is going to become a middle-income country soon and a developed one in the near future under the wise and skilful leadership of honourable Prime Minister Sheikh Hasina.

We have to endure the brunt of the man-made hazards, by which the people of developed countries are being affected today, in the coming days. If we prepare ourselves to prevent and mitigate these probable hazards from now, we will be able to create a 'safe Bangladesh' for the people of our country.  

The writer is a vice-chancellor at the Bangabandhu Sheikh Mujibur Rahman Digital University (BDU)








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