Fire and Fire Protection Flashcards
(9 cards)
a) State the five stages of fire development.
(5 marks)
b) Explain how passive fire protection can affect fire development.
(4 marks)
Ignition
Growth
Flashover
Fully Developed
Decay
Passive fire protection affects fire development by containing a fire in its compartment of origin for a given/specified period; this allows time for safe evacuation of a building and firefighters access to extinguish a fire.
This is done by preventing flames and combustion products from leaving the compartment and minimising heat transfer between compartments that can cause ignition.
Passive fire protection to the structure of a building gives structural stability preventing collapse before evacuation or fire fighters entering the building.
In terms of means of escape, explain what is meant by the term “place of reasonable/relative
safety” and give two examples of places of reasonable/relative safety.
A location inside a building that will offer protection from the effects of fire for a limited period of
time, enabling the occupants to make their way to a floor exit or place of ultimate safety. Typically,
this will be a protected corridor or stairwell.
Fire-resisting protected stairwell or corridor
– These are designed to remain smoke-free and withstand fire for a specific period, allowing people to escape from upper floors to the ground safely.
Refuge area or compartment
– Found in healthcare buildings or high-rise structures, these are fire-resistant zones where people, particularly those with limited mobility, can wait for rescue or assistance.
In relation to fire resistance, explain the difference between “insulation” and “integrity”.
(4 marks)
Integrity (E):
Definition: The ability of a building element to prevent the passage of flames and hot gases through it during a fire.
Focus: Stops fire spread.
Failure Example: Cracks or holes appear that allow flames or smoke to pass through, even if the element hasn’t collapsed.
Insulation (I):
Definition: The ability of a building element to limit the temperature rise on the unexposed (non-fire) side during a fire.
Focus: Limits heat transfer.
Failure Example: The unexposed side becomes so hot that it could ignite nearby materials or cause harm to people.
One of the measures used in assessing the way in which a material will react to fire is the
extent to which it is combustible. Identify three other factors that can be used in measuring
how a material reacts to fire.
Surface spread of flame
Heat release
Smoke production
Flaming droplets
Explain the issues and limitations that need to be taken into consideration when interpreting
fire testing and assessments.
Fire test results are essential for ensuring safety, but interpreting them requires understanding their inherent limitations.
1 Fire test report
fire test reports are only applicable to the product or
construction as tested with only limited variations permitted in the direct field of application of the
particular test method. Further, they have none of the quality control aspects of third party
certification.
- Assessment / Expert Judgment from an accredited fire test laboratory or suitably qualified fire
consultant
This level of assessment will offer some of the process required to achieve third-party certification,
such as an evaluation of performance from a range of tests (not just a single test), and an assessment
of evidence from tests to enable a ‘field of application’ to be determined. It is the next best thing to
third party certification, but offers none of the quality control aspects.
3 Third-party certification
An independent assessment is undertaken by a Certification Body, themselves accredited by
the United Kingdom Accreditation Service (UKAS in the UK), declaring that specified
requirements pertaining to a product, person, process or management system have been met.
Passive fire protections measures should be taken into account when developing plans for
building projects. One reason for this is to ensure that the correct checks are carried out at
the right times. Identify and explain two other reasons.
Work is carried out in the correct order;
* That nothing is missed e.g. failing to complete firestopping or provide fire retardants;
* That the correct materials are purchased and or used
* Compliance with regulations
a) Explain what is meant by the term “active fire protection” and state how active fire
protection differs from passive fire protection.
(3 marks)
b) Identify and describe two types of smoke detection system.
(4 marks)
Active Fire protection
Active fire protection is a form of protection measure that requires special energisation or a command
signal to operate, and includes:
* Detection systems
* Alarm systems
* Sprinkler/water mist systems
* Other fire suppression system, e.g. gaseous
* Smoke control systems
Many active systems such as a fire alarm will be actuated by a signal in response to the triggering of a
detector responding to heat, smoke, CO, CO2 etc. within its proximity. Alternatively, or in addition,
these systems will usually be operable by manual triggering, e.g. from a control room or ‘break glass’
box.
Other active systems, such as powder, gas or water filled extinguishers may also be activated via a
detector system, or operated manually via a portable, hand held fire extinguisher.
Active fire protection differs from passive fire protection as it is designed to surpress, extinguish a fire or remove combustion products rather than contain a fire in a compartment
Ionisation smoke alarm
Ionization-type smoke alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.
Optical smoke alarm
uses light scattering to detect smoke particles. These alarms contain an infrared LED that pulses light into a sensor chamber, and when smoke enters the chamber, the particles scatter the light. The scattered light is then detected by a photodiode, which triggers the alarm if a sufficient amount of light is detected
Ionisation smoke detectors
An ionisation smoke detector uses a radioisotope, to ionize the air, and where a change in air quality
due to the passage of smoke is detected, an alarm is generated.
Ionization detectors are more sensitive to the flaming stage of fires, such as smoke generated from
paper and wood, and will detect this type of fire before the smoke gets too thick during its early stages.
Optical smoke detectors
An optical smoke alarm (also called photo-electric smoke alarm) operates using the principle of light.
The alarm detector commonly contains a pulsed Infra-red LED which pulses a beam of light into the
sensor chamber every few seconds to check for smoke particles
Aspirating smoke detectors
An aspirating smoke detector is based around a central detection unit or chamber which continually
draws air through a network of small pipes. As the air moves through the sampling chamber, the
detection unit commonly uses a laser, to detect the presence of smoke particles in the chamber.
Identify five locations in a building where emergency lighting should be located.
(5 marks)
- Each final exit door
- Escape routes
- Intersection of corridors
- Outside each final exit and on external escape routes
- Emergency escape signs
- Stairways so that each flight receives adequate light
- Changes in floor level
- Windowless rooms and toilet accommodation
- Fire-fighting equipment
- Fire alarm call points
- Equipment that would need to be shut down in an emergency
- Lifts
- First-aid equipment
- Areas in premises greater than a given m² (e.g. in the case of HM Government Publication Fire
safety risk assessment, this would equal 60m²)
