Key considerations in hotel fire safety design

Hotels are often tall, large buildings with complex internal functions, high occupancy and lavish interiors. If a fire breaks out, these characteristics can make firefighting extremely difficult and cause devastating loss of life and property.

 

Fire protection system design has therefore always been a top priority in hotel development and design, particularly for high-rise hotels.

In terms of building use, hotels and apartments serve similar functions: primarily accommodation, supported by other commercial or service functions.

 

However, fire safety design for hotels is often more complex than for apartments, because hotels commonly present the following challenges:

· Guests unfamiliar with the building (short-term guests lack familiarity with the building, increasing evacuation time)

 

· Banquet halls and ballrooms (high occupant density puts greater pressure on evacuation)

 

· Atrium design (enhances the hotel's sense of space but presents fire safety design challenges)

 

· Open stairwells (save space but allow smoke and flames to spread quickly)

 

· Places of safety and escape routes (places of safety must meet strict requirements, while escape routes must be numerous and spacious)

Hotel fire protection system design therefore requires careful study of the building's architectural characteristics, functions and interior finishes, with detailed consideration of every aspect;

 

strict compliance with all applicable current codes; and reliable fire protection measures that are safe, fit for purpose, technically advanced and reasonably priced.

 

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An atrium can enhance a hotel's sense of space, extending the interior height beyond the limits of a single storey;

 

and, where it contains a garden or carefully designed sculptures, guests on upper floors can enjoy views of the courtyard through the atrium's open space.

 

Many high-end hotels therefore have atriums.

However, atriums often pose greater fire safety design challenges because they connect multiple floors to create an open space.

Without an atrium, these spaces can be divided into separate compartments by fire-rated floors and walls, greatly reducing the risk of fire and smoke spreading.

With an atrium, flames can spread more easily through the open space, while rising smoke entrains fresh air. Although this fresh air dilutes the smoke, the diluted smoke can still harm occupants on upper floors and even pose a potentially fatal gas hazard.

The large volume of an atrium reduces the radiant heat from flames reaching the uppermost floors, making it difficult for fire sprinklers to respond quickly.

 

This is because sprinkler heads are usually installed at the top ceiling. As hot smoke rises, surrounding air cools it, leaving it too cool to activate the sprinkler heads above.

 

If the sprinklers fail to activate, an initially small fire may develop into a large one, causing greater losses.

Hotel atrium design therefore requires particular attention.

The main approaches currently used to protect hotel atriums against fire are:

Installing smoke curtains: smoke curtains can be installed in open areas on upper floors.

 

Under normal, safe conditions, the curtains remain retracted, out of guests' sight, without affecting the atrium's appearance;

 

when a smoke alarm sounds, they descend automatically to prevent smoke entering upper floors through the atrium.

Precise smoke or flame detection: Because smoke may become diluted as it rises, conventional point-type smoke detectors may not respond during the early stages of a fire.

 

Laser smoke detectors or infrared flame detectors can be used in these circumstances.

 

These newer detectors can be installed near ground level in the atrium, cover a wide area and detect fires at an early stage, raising the alarm.

Automatic deluge fire suppression systems: These systems can address the slow response of conventional sprinkler heads because they are activated solely by smoke or flame alarms, rather than high temperatures.

 

Used alongside precise smoke or flame detection, an automatic deluge system can discharge jets of water early in a fire and extinguish it quickly.

 

Hotel designs generally include social spaces such as banquet halls and ballrooms, which have some of the highest occupant densities of any functional area in a hotel;

 

in practice, these halls also host DJ events or operate as nightclubs or clubs, further increasing occupant density.

 

Fire safety design therefore needs to address the following three points:

· Hotel banquet halls and ballrooms generally require multiple escape routes so that crowds can be evacuated promptly within a short time;

 

· Banquet halls and ballrooms should have ceilings as high as possible and natural or mechanical smoke extraction systems. Removing smoke during a fire reduces harmful gas concentrations and extends the time available for safe escape.

 

· Fire sprinkler systems are generally essential in banquet halls and ballrooms, particularly banquet halls with capacity for more than 1000 people.

 

 

Ideally, stairwells should have their own fire-rated walls and doors to provide effective fire separation from the hotel's functional areas.

 

In practice, hotel designers often favour open stairwells, which reduce the space required for stairwell construction and improve connections within the building.

Like atriums, open stairwells make it easier for flames and smoke to spread, reducing safety.

 

Hotels with open stairs therefore often need additional smoke extraction systems to remove smoke promptly and give guests more time to escape.

 

Fire sprinkler systems are also generally essential.

 

To save building space and increase guest room numbers, developers may consider providing only one stairwell or keeping the number of stairwells to a minimum.

 

During a fire, the relatively confined stairwell space and high smoke concentrations mean visibility can drop immediately when a guest opens a stairwell door.

 

Where a hotel has only one stairwell, or a stairwell serves more than 250 people, fire safety design requires visibility to remain at least 5 metres during evacuation.

If the developer is unwilling to add more stairwells, installing a stairwell pressurisation system is a good solution.

 

A pressurisation system works by adding air supply outlets in the stairwell. When guests open a stairwell door, air pressure prevents smoke entering from the corridor, maintaining visibility inside.

Pressurisation is a relatively complex system: insufficient airflow will not effectively prevent smoke entry;

 

excessive airflow can keep out more smoke, but may prevent guests from opening the stairwell doors.

 

Designing a pressurisation system therefore requires fire engineers and mechanical engineers to work together on factors such as outlet locations and airflow volumes.

 

 

Behavioural researchers have found that people tend to escape along familiar routes, rather than strictly following the escape routes predetermined by designers.

 

For example, hotel guests usually enter through the lobby entrance and check in there.

 

If a fire alarm sounds, guests may first gather in the lobby and then leave through the lobby entrance.

 

This is because guests remember the route to the lobby clearly and consider escaping along a familiar route a safer choice.

This behavioural principle of familiarity can put greater pressure on hotel evacuation: the planned ideal routes may go unused, while main entrances and exits become overloaded and evacuation bottlenecks develop.

 

To address this, hotel fire safety design should provide more spacious doors and passageways at main entrances and exits. Larger main doors and wider passageways can effectively reduce queuing time during evacuation.

Safe areas within the building can also provide guests with additional protected space during escape.

 

However, a hotel's elevated gardens or balconies cannot simply be designated as safe areas.

 

In New Zealand, a safe area must meet all of the following conditions: enclosure by fire-rated walls and doors; a sprinkler system; sufficient space for the designated number of people; and enough routes connecting to the outside of the building.

 

Clearly, designing a safe area within a building is no simple matter, so hotel designers need to consider whether one is necessary;

 

and, if one is provided, how to maximise savings on fire protection construction costs, among other considerations.

 

In columns in previous issues of YIJU New Zealand, we have repeatedly discussed passive fire protection requirements in apartment development.

 

These requirements are equally important in hotel development, and may be even more demanding.

Passive fire protection for penetrations means that openings created when drainage pipes, cables and heating, ventilation and air-conditioning services pass through fire-rated walls and floors must receive fire protection to the same rating as those walls and floors.

 

Auckland Council explicitly requires passive fire protection in new buildings to meet new-build standards and achieve full compliance.

For passive fire protection of building penetrations, we recommend a detailed design approach: complete the detailed design and select penetration protection systems early, before applying for building consent.

 

This offers many benefits: the basic design can be adjusted, and passive fire protection construction and material costs can be reduced;

 

the detailed design documents can be used to tender the passive fire protection work, allowing selection of the most competitively priced contractor;

 

and at completion, having detailed design documents makes it easier to pass council inspections and obtain the fire engineer's PS4.

As Auckland's passive fire protection requirements become stricter and clearer, we believe similarly stringent requirements will soon be introduced elsewhere in New Zealand.

 

 

Located in central Auckland, this hotel has 12 storeys, including 2 basement levels.

 

The ground floor connects to the main street and also serves as the reception lobby.

 

To enhance the hotel's sense of space, the designers created a large atrium connecting the ground floor with every floor above. A large banquet hall and ballroom are located on the first floor.

We considered the following measures in the fire safety design:

· Install flame detectors and laser smoke detectors on the two levels above the atrium to detect flames or smoke at an early stage and provide a prompt fire alarm.

 

· Install a deluge system within the atrium to address the risk of the sprinkler system failing to respond because of the atrium's height.

 

The deluge system does not need high temperatures to activate. Instead, flame detectors and laser smoke detectors activate it promptly, releasing jets of water to control the fire.

 

· Install a stairwell pressurisation system to prevent corridor smoke entering the stairwell and maintain visibility inside.

 

· Design smoke extraction systems for the banquet hall and ballroom to remove smoke promptly and extend the time available for escape.

 

· Widen the lobby passageways and main doors and arrange them appropriately, allowing more guests to escape into the lobby, reducing queuing time and resolving evacuation congestion.

 

About the author: Alex Zhu
Dr Alex Zhu is a fire engineer and project development manager at Origin Fire (www.originfire.co.nz), a leading New Zealand building fire consultancy. He has many years of experience in building fire engineering design, practice and management, and has contributed to the fire engineering design and construction of numerous large buildings.

His doctoral research involved fluid dynamics, examining airflow dynamics and their relationship to fire safety design. His research is directly applied to Origin's precise modern fire engineering designs, using advanced virtual technology to build 3D fire simulations to understand where fires occur and how quickly they spread through large buildings.

 

About the author: Michael James
CEO and chief engineer of Originfire (www.originfire.co.nz), a leading New Zealand building fire consultancy, with more than 25 years of experience in building fire engineering design, management and practice. He has contributed to and led the fire engineering design and construction of numerous large buildings.

Michael has extensive experience, including working with city councils and fire service providers. He offers distinctive solutions to fire safety challenges in apartment buildings, high-rises and large buildings. Michael previously served as managing director of Pacific Engineering Consultants and is currently New Zealand president of the Society of Fire Protection Engineers.