Fire Accidents in Building

Foreword

12 min readMay 11, 2021

All of us might have noticed the disturbing news of the repeated Fire Accidents in Hospitals, Residential Buildings and Industries over last a few months in many parts of the country, which has resulted loss of many lives, mainly the poor covid 19 patients in Hospital. The fire in Sunrise Hospital in Mumbai, Vijay Vallabh Hospital at Virar and Welfare Hospital at Bharuch are as fresh as yesterday. To our utter surprise none or most of these buildings did not have totally Non-functional Fire Fighting System. And some of these properties managed to get Fire safety certificate from the concerned Department around a month before the fire took place.

Highlighted below about the history of fire accidents covering number of deaths, causes of fire, characterization of materials in use in building, its behaviors under fire, Fire protection and Firefighting system in buildings, national Building Codes and vis a vis the role of Fire safety Officer.

Definition of Fire & Its History

Fire is the visible effect of process of combustion — a special type of chemical reaction. It occurs among oxygen in air, some fuel and heat, which are necessary for the fire to happen. This is known as Fire Triangle. Combustion happens when fuel reacts with oxygen to release heat energy.

The oldest fire recorded in Earth was identified from charcoal in rocks formed during late Silurian period around 420 million years ago. The first stage of human interaction with fire, perhaps as early as 1.5 million years ago in Africa is likely to be opportunistic, Fire may have been conserved by adding fuel, which is dung, that is slow burning.

Fire would have been useful not only for light and warmth at night but also to frighten off predatory animals and the smoke would have been effective to keep away the insects. This ability of stretching fire would have been a phenomenal step by human being in the development of civilization.

History of Fire Accidents in India and Vis a vis Death

Fire Accidents in India by category of Building

Fire in Buildings

Building Design

Buildings need to be designed to offer a fair level of fire safety and minimize the risk from heat and smoke. The major objective is to reduce the potential death or injury of the residents and as well as others like fire and rescue services team along with the protection of contents. Also, it is expected the building to function after adequate repair. The risk to the neighboring buildings also needs to be considered and as well as environmental pollution.

Fire Growth

Fire passes through a series of stages from the moment of ignition to a stage where most of the combustible materials catches fire. A critical stage occurs when fire has touched the ceiling resulting transfer of radiant heat back to the surface of fuel significantly. This usually happens when the temperature at ceiling reaches at around 550 deg C. Thereafter, balance combustible materials would arrive at its fire points and ignite within 3 to 4 seconds. This sudden transition is known as Flashover. If there is insufficient ventilation during the growth period, Fire may not reach to the stage of Flashover and die out or continue to smoulder. A fresh supply of oxygen at this stage through opening of door or window may turn out to be hazardous.

After the stable face of fire, followed by Flashover flaming is seen throughout the enclosure and highest temperature is attained. At this stage the fire resistance coating on the materials forming the enclosure need to play a critical role by sustaining the maximum temperature and the period of continued fire enabling to protect the structure from collapsing, which makes the rescue of people and fire service agency to perform better.

Heat

The severity of fire can be assessed by the amount of heat load generated. The quantum of potential fuel within the building is known as Fuel load. This also depends on the fabric of the building and the character of the content. The rate of burning shall be fully dependent on type of fuel load and available ventilation.

Smoke

Smoke is a combination of gaseous and partly solid products (burnt and unburnt) as effect of combustion. All smoke is dangerous. Ideally, its production should be limited and movement under control. Most of deaths in fire accidents is caused by smoke either by inhalation of toxic gases or carbon monoxide poisoning.

Categorization of Materials Used in Building Construction

All building materials can be grouped as follows:

a) Combustible b) Non — Combustible

c) Fire Resistant d) Ignition Resistance

Combustible

Combustible materials are those which catch flame easily and burns. It could be classified based on its fire rating, which is related to Flame spread Index. The flame spread rating is determined by exposing the materials to a gas flame in a horizontal furnace.

Details of Classification of Flame spread Rate is given as below:

Class A: Flame spread Index <25 (Numerical)

Class B: Flame Spread Index 25 to 75

Class C: Flame Spread Index >75

Another parameter of assessment of Combustible material is Heat Release Rate (HRR), which is measured by loss of mass of a burning material or by total rate of energy release during burning.

Non- Combustible

This group of materials are not capable of undergoing combustion under specified conditions. The evaluation of the non- combustibility is done by testing the material in a vertical Tube Furnace at 750 deg C, four specimens are tested at a time and three of them must meet the specified characteristics denoted as CI and CII. Materials under CI group are preferred as construction materials for exterior uses as it deemed to be non- combustible. Materials under CI losses maximum 50% or less of its weight during test and maintains surface temperature as 30 deg C along with no flaming after 30 seconds of burning.

Fire Resistant

Fire resistant materials or its assembly are designated based on their capability to contain a fire within a compartment or building or continue to support the structural function in the event of a fire (internal) providing enough time to people to evacuate.

Testing is done in a large vertical furnace exposing a panel or wall to radiant heat from gas burners. The duration of test ranges from 20 minutes to several hours, depending on the desired rating of the material/assembly at a temperature of 925 deg C inside the furnace. In this case also material/assembly is graded as A, B and C but signifying different characteristics.

Ignition Resistant

This group of material has the lowest rate flame spread after being subjected to a specified wetting and drying weather cycle. These materials are tested in a Horizontal Flame Spread Tunnel and the duration of test is 30 minutes against the duration of flame spread test of 10 minutes. Materials with pressure impregnated fire retardant coating results very slow burning and may be recommended for exterior use in building.

Behaviors of MOST Used Building Materials at Elevated Temperature

In construction major and materials used are concrete, steel and Timber (very less in comparison to two other materials).

Concrete and steel are non-combustible materials, its integrity can be compromised at high temperature, Reinforced concrete can actually resist the spread of and as well as bear high temperature till the spalling of concrete begins.

Steel

Structural steel can withstand high temperature around 425 deg C, before it begins to soften. Steel loses half of its strength at temperature between 600 to 650 deg C and will pose a risk of failing. Colour of steel changes according to its temperature as it undergoes a process known as thermal expansion. The colour changes from pale Yellow (220 deg C) to a wide range of Purple shade (260- 285 deg C) to blue (290–330 deg C) and finally to Red, yellow and White Sparkle at 1400 deg C. After the fire ends, steel would try to contract to its original shape, presuming the deformation is elastic. In case of a permanent set occurs, which threatens integrity based on its original and residual loads.

If a fire is below 700 deg C for less than 20 minutes, the reduction in stiffness and strength is temporary only. It may look deformed; but it would go back to its original property though may be buckled.

Steel starts melting at different temperature depending on its composition. Carbon Steel starts melting at 1130 deg C and when there is zero content of carbon, steel melts at 1492 deg C. However, steel would melt totally in liquid form at 1550 deg C.

The most cost- effective method to improve fire resistance property of structural steel is by applying intumescent coating. This special coating acts by swelling up in to a layer of carbonaceous char on exposure to heat and protects the steel from further damage. This coating slows down the transfer of heat to steel, delaying the time to reach its critical temperature. Thicker coating offers higher resistance.

Alternatively, cementitious coating with vermiculite, gypsum, etc., is used, forming a thick layer around steel resisting the fire, Cementitious coating is well suited for dry environment, where higher level of moisture is absent in the air.

Concrete/ Structural Concrete (RCC)

Concrete and masonry do not catch flame and also do no not spread fire. It can withstand fairly high temperature. However, the structural concrete starts changing its behaviour at a certain high temperature due to several factors.

The behaviour of structural concrete member at elevated temperature depends on the followings:

a) Composition of concrete

b) Thermal conductivity

c) Moisture content / water cement ratio & Permeability

d) Aggregate minerology

e) Cement hydration products

The following changes may take place in reinforced concrete on exposure to fire:

a) Uneven volume changes in affected members resulting in distortion, buckling and cracking. The temperature gradient is extreme from ambient (21 deg C) to higher than 800 deg C at source of the fire and near the surface.

b) Spalling of concrete rapidly expands at the extreme heat region near the source of fire. Some aggregates expand in bursts, spalling the adjacent matrix.

c) Cement mortar converts to quick lime at temperature of 400 deg C, thereby, causing disintegration of concrete

d) Reinforcing steel loses tensile capacity as the temperature rises.

e) Once the reinforcing steel is exposed by spalling action, the steel expands more rapidly than the surrounding concrete, causing buckling and loss of bond to adjacent concrete where the reinforcement is fully encased.

At high temperature the spalling of concrete occurs due to flow of water vapour outward and accumulation of condensed water vapour (moisture clog), which finally increases the pore pressure at saturated front and thermal expansion.

Aggregate in concrete plays an important role. Ability of absorbing heat by an aggregate fast without increase in temperature much, is good against fire resistance. Aggregate with high thermal conductivity is bad performer against fire. Porous aggregate and aggregate with high specific heat resist fire better.

Permeability in concrete leads to lesser distress. High strength concrete with silica fume and low water cement ratio may cause explosive spalling.

Use of Plastic Fibre in concrete

Incorporation of plastic fibre improves the performance of concrete under fire. Plastic fibre like polypropylene helps in relieving the pressure created within the concrete. Moisture content of 2–3 % in concrete may not cause problem. Plastic fibres melt at 160 deg C and release the moisture by occupying the space, which may reduce damages in concrete. However, plastic fibres do not improve any other property under fire.

Performance of Unprotected Materials Under Fire

Recommended Use of Concrete Against Fire

Fire Protection System in Building

Two types of Fire protection systems are usually installed in any major building-

a) Passive Fire Protection, & b) Active Fire Protection.

Passive Fire Protection

This system breaks the building in to compartments and prevents fire through the fire resistance walls and floors. Passive Fire Protection (PFP) is based on structural fire

protection and compartmentalization for safe exit of the occupants out of the building and allow entrance of fire brigade team in to the building successfully.

a) Structural fire protection

It ensures the stability of structural elements in a building in case of fire. This may be achieved by applying suitable products on the structural elements in a building, like boards, paint or spray.

b)Compartmentalization

It is installation of Fire barriers, Fire walls, Fire partitions and Smoke barriers, which help to prevent the flow of fire.

c)Opening Protection

Fire doors and windows along with Fire & Smoke dampers and sealing of opening where air ducts enter fire and smoke resistant assemblies.

d)Fire Stopping Materials

This is used to limit fire spread through penetrations in a fire barrier.

f) Others

Other areas of PFP are cable coating, Joint system and Perimeter fire barriers.

Passive Fire Protection prevents the spread of fire successfully, but experts recommend redundancy in fire protection system.

Recommendation as Per Euro Code

Active Fire Protection

Active Fire Protection (AFP) system includes fire protection elements that need an action to function. The action may be manual like Fire extinguisher or Automatic Sprinkler system. These will help to overpower and stop a fire which has begun. An Alarm system will alert the fire department to trigger the sprinkler and to shut fire exits.

A well-functioning Alarm system makes it easier to stop fire, before it causes any major damage.

In addition, Fire Hose reels and Fire hydrant system also help the fire brigade team to initiate faster action.

Fire Retardant & Fire Resistance Coatings

There is a confusion between Fire retardant and Fire-resistant material.

The wide range of materials in form of organic, inorganic, synthetic or natural used in buildings are easily frameable or readily burns on exposure to high temperature and fire. To improve upon its property, a special coating is used over the surface of material.

This coating material limits the flame spread and smoke development.

Fire retardant coatings are typically based on chlorinated alkyds or brominated epoxy resin and filled aluminium hydroxide or a combination of chlorinated paraffin and antimony oxide system.

Fire resistance coating are mainly predominant in protection of structure, which occurs after flash over.

Fire resistance coating used on structural members, walls, floors, etc., is primarily intumescent coating. The major constituents are 15% of dehydration agent, 18% of foaming agent, 7% of resin binder and 40% of solvent. There could be other combination too.

The mechanism of functioning of intumescent coating is to undergo an endothermic decomposition reaction at an elevated temperature, that causes coating to swell and form in to a highly porous, thick and thermally stable char layer having low thermal conductivity.

National Building Code

National Building Code (NBC) Chapter 4 has set very clear guide lines regarding Fire and Life Safety for different types of building. It includes the fire protection systems based on passive and active fire protection systems. In addition, it suggests to have emergency lighting arrangements, fire lift, fire tower (enclosed staircase), roof exits. Any building following the guide line given in NBC can probably stop damages in case of a fire accident.

Role of A Fire Safety Officer

There is a critical role to play by Fire Safety Officer (representative of State Govt), who is supposed to inspect buildings to ensure safety and regulation codes are followed and guide on periodic maintenance, train and educate building staff. Finally, after inspection and evaluation, he is also supposed to notify violation, if any to the concerned authority for necessary rectification, installation, and if required, recommend penalization on failure by building society/authority.

Conclusion

Fire accidents are too frequent in our country even now, though the total number of accidents have a reducing trend over a number of years. As seen in last few months almost all the fire accidents occurred due to nonfunctional of Active firefighting system. It resulted killings of significant number human being and as well as loss of assets too. In my opinion this could be treated as serious negligence and criminal offences.

I believe the fire authority is equally guilty for not doing justice to their job. As reported in the news paper Vijay Vallabh Hospital at Virar managed to get the Fire safety clearance one month before the fire occurred. Fire Authority must strictly evaluate before releasing any safety clearance certificate

Also, there is not enough clarity among the plenum of people regarding the devasting fate of any serious fire accident, hence, hardly any safety measure is installed to protect the fire.

An awareness programme needs to be undertaken in wide scale across the nation on war footing involving residents/ users, Builders, Contractors, Designers and Fire Safety Authority. In fact, Fire safety authority must take the lead, which is an important part of their job profile. It may be worth to reward the builder/contractor, if the Passive & Active Fire protection systems are in place in the building.

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