Fire safety in modern indoor and built environment

Introduction

The rapid rise of the economy all over the world has led to many large-scale new or renovative construction projects with tall building complexes. ¹ People change living style in travelling around frequently with mass transport systems through intra-city subway systems, inter-city high-speed railways and intercontinental air passages. They also enjoy leisure sea cruising voyages. As the number of fires, including arson and terrorist attack fires, appears to be increasing in the past decades, fire safety has to be considered carefully in all such indoor and built environment. There are even conflicting requirements ² on green energy use and fire safety. Using flammable clean refrigerant may lead to explosions. ³ Design and operation of indoor and built environment must include protection against fire and explosion hazards. Associated standards and regulations for the design, operation and maintenance of the building or indoor enclosure have to be kept updated with the scenario together with the advancement of science and technology.

This special issue is to present the latest developments in fire safety in indoor and built environment and possible implications in the associated regulations and standards. City fires, tunnel fires, green building fires, fire protection systems and fire safety management are included in this special issue.

Fire safety of tall buildings as an example

Numerous tall buildings were built in the past two decades, even residential buildings are up to 80 storeys. ⁴ A supertall building is taken to be of height over 300 m by the Council on Tall Buildings and Urban Habitat (CTBUH). ⁵ The term ‘very tall building’ ⁶ is used by the Society of Fire Protection Engineers. Buildings taller than 40 storeys are understood as supertall (or ultra-highrise) buildings in the Hong Kong Special Administrative Region (HKSAR). ⁷ Different terms were used for very tall buildings, ‘mega-high-rise buildings’ ⁸ and ‘super-high-rise buildings’. ⁹ The problems when a very tall building catches fire are long evacuation time for occupants, rescue difficulty for high occupancy, impossible from outside to suppress the fire at high level, etc.

Evacuation is the key part in a fire safety strategy for providing fire safety objectives.^10,11 Evacuation time in a 65-level residential building ⁷ cannot be shorter than 25 min even for low occupant loading. Evacuation time for offices in a supertall commercial building was studied. ¹² It would take almost an hour ¹² in a 300-m tall building under normal occupancy. Additional evacuation routes cannot be provided easily for existing supertall buildings. Using lifts would shorten the evacuation time, but there is controversy in using lifts in case of fire. Consequently, refuge floors and more staircases are provided. But is it adequate?

More challenges in tall buildings are coming from sustainability, green energy, use of ecological products, high levels of automatization, smart solutions and artificial intelligence. While ordinary buildings usually cover basic functions for people’s lives, modern tall and supertall buildings significantly go beyond these borders. All these predetermine that tall buildings in their essence represent an emanation of modern scientific achievements and the efforts of architects, engineers and builders to present a new kind of lifestyle in an urban environment. There are various ways of providing fire safety, from complying with regular prescriptive codes (PC), to specific measures such as fire engineering approach, performance-based designs and engineering performance-based fire codes for extraordinary buildings where the PC could be inadequate due to various reasons. This only shows the seriousness of the safety measures that cannot be resolved without smart solutions and the creation of a sustainable environment based on the achievements of the latest scientific research and innovative technologies.

Fire safety requirements

Basically, each country has the main commitments and responsibilities in ensuring the safety and security of the people, according to their laws, where fire safe indoor and built environment is a big challenge all around the world. In some countries like Bulgaria, used as a case study for the current research, there are no real experience as well as in-depth research and full-scale burning tests concerning tall buildings. Bulgaria’s government targeting on encouraging investors as much as possible for sustainable, green and eco-friendly development of this type of tall construction in compliance with all regulations, both at the national and European Union level, as a result of the emerging crises with the supply of natural resources and a profound reorientation of the entire economy to green and renewable resources in the coming decades. In this regard, although there are strict fire safety regulations for tall buildings in Bulgaria, they will be reviewed and checked whether there are significant inadequacies by comparison with countries having a large number of tall buildings and experience, like the HKSAR and Mainland China. HKSAR has many tall buildings over 150 m, where over half of the top 100 tallest residential buildings in the world are located in HKSAR, with some of them over 200 m in height. Moreover, six of the top 10 tallest completed buildings in the world measured by height to architectural top, which is the most widely utilized classification in the rankings of the ‘World’s Tallest Buildings’, are located in China. ⁴

As a rule, when more people are living or working in a tall building, the greater would be the fire load density. ¹³ As there are two types of buildings – newly built and old ones, a very big challenge is to ensure fire safe indoor and built environment in existing old tall buildings. These are usually around 10-storey buildings that fall on the edge of the tall building definitions but do not meet the codes, and belong to the ‘status quo ante’ case. Usually, these buildings do not have two emergency exits, they do not have a fireman lift, and they do not have devices for overpressure in the staircases.

Recent history shows that the topic cannot be neglected because fires in tall buildings are not uncommon. ¹⁴ Unfortunately, there are lots of examples of tragic experiences in tall buildings: the Grenfell Tower fire in a 24-storey apartment block in London with a total of 72 deaths caused by hazardous combustible materials used for facade insulation ¹⁵ ; fire in the 25-storey Joelma building in São Paulo, Brazil, with a total of 189 deaths; fire in the 21-storey Taeyongak Hotel in Seoul, South Korea, with a total of 163 deaths; as well as the terrorist attacks in New York which are stated as a benchmark of the new beginning of fire safety science in the whole world with a total of 2606 victims; and many more.

Inadequacy of existing fire codes or even the absence of certain rules has to be reviewed and identified as soon as possible, because they could be the major causes for such painful lessons.

Fire codes in several areas with active development

The definition of tall buildings in Bulgaria generally means a building above 28 m. These buildings are categorized into four groups for the purpose of fire safety as from 28.01 m to 50 m – Group I, from 50.01 to 75 m – Group II, from 75.01 m to 125 m – Group III and over 125 m – Group IV. ¹⁶ The definition of a tall building (which is termed as high-rise building) in HKSAR means any building of which the floor of the uppermost floor exceeds 30 m.^17–20 In Mainland China, all residential buildings above 27 m and all office buildings above 24 m are defined as tall. They are additionally categorized into two groups for the purpose of fire safety as: Group I – residential buildings above 54 m and office buildings above 50 m; and Group II – residential buildings from 27.01 m to 54 m included and office buildings from 24.01 m to 50 m included. ²¹

Fire safety requirements can be generally specified according to:

New challenges and fire engineering approach

The new challenges for sustainability, green energy, eco-friendliness, smart solutions and the use of artificial intelligence force the use of fire engineering approach (FEA). It can be described as an option where the fire engineers shall demonstrate that their innovative design and smart solutions are equivalent to the safety level of PC. However, there is no extensive data, a comparison methodology is usually adopted. While it is very important to use appropriate design fire for FEA, the performance-based design has clear acceptance criteria and the engineers work with clear supplementary data obtained from fire tests and reliable design handbooks. Engineering performance-based fire code is a specific approach and very few professionals are able to follow it. It takes time to transfer previous fire data to this code system and there may be a high compensation cost when a big fire occurs.

In HKSAR, fire engineers mainly use FEA to provide an acceptable fire safe environment in buildings not covered by the PC, such as supertall buildings and buildings with tall atria as PC cannot be applied in buildings beyond their specification range. There might be adverse effects such as water spray discharged from high headroom atrium sprinkler and putting at risk the effectiveness of the total sprinkler performance in atriums, ²² on top of smoke control.^23,24 In this kind of buildings, a special innovative approach and new technologies are needed to provide fire safe indoor and built environment for the people. In Bulgaria, there are not many buildings that need a fire engineering approach but this is a good opportunity to take a look and learn from experienced regions in this sphere like the HKSAR and Mainland China. As a global rule, the fire engineering approaches for these buildings are increasingly accepted on a case-by-case basis by the national authorities. Also, the latest expectations of the people are that the solutions found must meet high sustainability, green and ecological standards, which makes the task even more complex.

Cost reduction is a strong driver for performance-based fire safety design. While it is an important factor to consider in engineering solutions, it needs to be used with care. Cost reduction cannot justify unsafe solutions, nor can it be recommended without an analysis of the hazardous consequences. The pressure of cost reduction can result in unjustified fire scenarios in fire hazard assessment. Therefore, more attention should be paid to hidden fire problems in the approved fire engineering approach/performance-based design projects. ¹⁹

Innovative practices and new technologies in fire safety science are important tools for engineers in ensuring effective fire safety indoor and built environments using FEA faced high sustainability, green and ecological challenges. They are diverse methods to ensure safety for the extraordinary building which cannot comply with the PC. Only in the last decade, there have been many options for innovative materials for which properties should be thoroughly researched.

Research for safe environment

Important research topics for new technologies and methods for the purpose of FEA, as an option to solve the challenges, are suggested.

A recapitulation

This special issue is to present the latest developments in fire safety in indoor environments and possible implications in the associated regulations and standards. City fires, tunnel fires, green building fires, fire protection systems and fire safety management are included.

Some important points had been studied. For example, evacuation has been identified as a key fire safety concern of supertall buildings. Occupants are supposed to leave the fire room to a safe place with minimum injuries and life loss. The fire codes for safe egress are frequently updated. However, more challenges are coming. There is another Special Issue planning with a tentative title: Fire Safety Regulations and Standards in Indoor and Built Environment - Revisiting and Update.

The aim of this special issue is to provide a review and update on standards/regulations on ‘Fire Safety’ and ‘Explosion Hazards’ associated with building environments of different countries and organizations. Colleagues are invited to present the latest developments and requirements in research in relation to fire safety and to identify implications in the updating of the associated regulations and standards. Both research and review papers on the following topics are welcome:

• Development and update of standards/regulations on ‘Fire Safety’ and ‘Explosion Hazards’ associated with building environments of different countries and organizations.