NFPA 72 Understanding Supervisory Signal–Initiating Devices: Simplified Guide with Key Requirements"

Supervisory Signal–Initiating Devices

This post explains the requirements for supervisory signal–initiating devices used to monitor systems like valves, pressure, water levels, and temperature.

1. Control Valve Supervisory Signal–Initiating Device

• Purpose: Monitors the position of control valves.
• Signals:
  • Off-normal signal: Triggered when the valve moves from its normal position.
  • Restoration signal: Triggered when the valve returns to its normal position.
• Trigger Conditions: Off-normal signal is activated:
  • Within 2 handwheel revolutions or
  • Within 1/5 of the valve’s travel distance.
• Restrictions: Device must not interfere with valve operation, obstruct indicators, or prevent maintenance.

2. Pressure Supervisory Signal–Initiating Device

• Purpose: Monitors system pressure for deviations.
• Signals:
  • Off-normal signal: Triggered when pressure increases or decreases.
  • Restoration signal: Triggered when pressure returns to normal.
• Applications:
  • Pressure Tank: Detects changes of ±10 psi (70 kPa).
  • Dry Pipe Sprinkler System: Same as pressure tank.
  • Steam Pressure: Detects low pressure before it falls below 110% of the required level.
  • Other Sources: Must comply with local authority requirements.

3. Water Level Supervisory Signal–Initiating Device

• Purpose: Monitors water levels to ensure safe operation.
• Signals:
  • Off-normal signal: Triggered when water level rises or falls outside limits.
  • Restoration signal: Triggered when water level returns to normal.
• Applications:
  • Pressure Tanks: Triggered by a ±3 in. (70 mm) change.
  • Other Containers: Low water signal triggered by a drop of 12 in. (300 mm).

4. Water Temperature Supervisory Signal–Initiating Device

• Purpose: Monitors water temperature in freezing conditions.
• Signals:
  • Off-normal signal: Triggered when water temperature drops to 40°F (4.4°C).
  • Restoration signal: Triggered when water temperature rises above 40°F (4.4°C).

5. Room Temperature Supervisory Signal–Initiating Device

• Purpose: Monitors room temperature to prevent freezing.
• Signals:
  • Off-normal signal: Triggered when room temperature drops to 40°F (4.4°C).
  • Restoration signal: Triggered when room temperature rises above 40°F (4.4°C).

Penetratio Firestop Systems: Key Ratings, Applications, and Standards

Penetration Firestop Systems

Penetration firestop systems are those that penetrate one side, as is the case with a membrane penetration, or both sides, in the case of a through penetration. These systems are used to restore the hourly rating of a tested vertical or horizontal assembly when penetrated by elements like pipes or cables. The systems are essential in maintaining the integrity of fire-rated barriers.

Key Elements of Firestop Systems

• F Rating: Evaluates the time the system prevents flame passage (in hours).
• T Rating: Measures the time the system limits temperature rise on the unexposed side.
• L Rating: Determines air leakage rates at specific pressures and temperatures.
• W Rating: Assesses water resistance and performance after water exposure.

Explanation

Firestop systems are critical for ensuring the safety of fire-rated assemblies like walls, floors, and ceilings. They restore the fire resistance rating after these assemblies are penetrated. The ratings (F, T, L, W) are determined based on standardized tests like ASTM E814 and UL 1479, which assess performance against flame, temperature rise, air leakage, and water exposure.

Determining Fire Barrier Location and Rating

The process of determining fire barrier locations and their hourly ratings is essential for ensuring building safety and compliance with fire protection standards. Here's a detailed breakdown:

1. New Construction Projects

• Architectural Drawings: Fire-resistance-rated barriers are typically marked in architectural blueprints. These include walls, floors, or ceilings with specific fire ratings.
• Fire Protection Engineer Input: If a fire protection engineer is involved, separate fire barrier drawings are often provided, showing precise locations and their hourly fire resistance ratings.

2. Existing Construction

• Limited Guidance: In older buildings, fire-rated barriers may not be clearly indicated in the original drawings or may not exist at all.
• Building Study: A thorough examination of the structure and the local building codes is required to locate fire-rated assemblies.
• Common Fire-Resistant Areas:
  • Floors: Typically rated for 1 or 2 hours to provide fire separation between stories.
  • Shafts and Stairs: Enclosed vertical spaces like stairwells and elevator shafts are usually rated for 1 or 2 hours, depending on the building’s height.
  • Special Rooms:
    • Boiler Rooms, Incinerator Rooms, and Large Storage Areas: Rooms larger than 100 ft² (9.3 m²) often have 2-hour fire-resistance ratings.
    • Paint Shops and Maintenance Areas: Generally require 2-hour-rated construction.
  • Tenant and Dwelling Separations: Spaces between different tenants or units (like apartments) are often rated for 1 hour.
  • Corridors: Hallways leading to exits typically require 1-hour ratings, though this may vary if automatic sprinklers are installed.

3. Special Cases

• Smaller Storage Rooms (<100 ft² or 9.3 m²): These usually require only a 1-hour fire resistance rating.
• Trash and Linen Chute Access Rooms: Commonly separated with 1-hour-rated barriers.
• Laboratories: Often classified for 1-hour fire separation due to the nature of activities conducted there

  Multiple Choice Questions

  1. What does the F rating measure in firestop systems?

  1. The system's resistance to water.
  2. The time to limit temperature rise.
  3. The time to withstand flame passage.
  4. The air leakage rate.

  Correct Answer: C

  2. Which test generates both F and T ratings?

  1. ASTM E814
  2. UL 1479
  3. NFPA 101
  4. ISO 9001

  Correct Answer: A

  3. Which rating is optional in UL 1479 but not included in ASTM E814?

  1. F Rating
  2. T Rating
  3. L Rating
  4. W Rating

  Correct Answer: C

  4. What is the main purpose of penetration firestop systems?

  1. To protect against water damage.
  2. To restore fire-rated assembly integrity after penetration.
  3. To provide ventilation in enclosed spaces.
  4. To reduce noise transmission between rooms.

  Correct Answer: B

Understanding the Storage and Discharge of Liquid Carbon Dioxide

Properties of Carbon Dioxide: Storage and Discharge

Carbon dioxide (CO₂) is stored and discharged under specific conditions to ensure safety and effectiveness in fire suppression. Its storage methods and discharge properties are critical in maintaining its effectiveness as a fire-extinguishing agent.

Storage of Liquid Carbon Dioxide

Liquid carbon dioxide can be stored in high-pressure cylinders or low-pressure refrigerated containers. High-pressure cylinders have a storage temperature that varies with the surrounding environment, while low-pressure systems are designed to maintain a storage temperature of approximately 0°F (-18°C).

High-pressure cylinders typically range from 5 lb (2.27 kg) to 120 lb (54.4 kg) in capacity, whereas low-pressure storage units have capacities ranging from 750 lb (340 kg) to a massive 60 tons (54,431 kg) per unit.

High-pressure cylinders are equipped with siphon tubes that draw liquid CO₂ from the bottom of the cylinder. The contents are then discharged through a control valve to the fire zone. When the discharge valve opens, the entire content is typically released.

Discharge Properties

The discharge of liquid carbon dioxide has a white, cloudy appearance due to the formation of a water fog as the air is cooled below its dew point. This fog results from both the cooling of the air and the fine dry ice particles produced. The water fog can persist for a time after the dry ice particles have sublimed.

Even after the fog dissipates, dangerous concentrations of CO₂ may remain in the area, making proper ventilation crucial during and after discharge.

Static Electricity Concerns

During the discharge process, dry ice particles can accumulate static electricity. Additionally, static charge can build up on ungrounded discharge nozzles. To avoid the risk of electric shocks or unwanted static discharges—especially in explosive environments—all discharge nozzles must be grounded.

Vapor Density of CO₂

Carbon dioxide vapor is much denser than air. Its density is one and a half times greater than air at the same temperature. As CO₂ vapor discharges to the atmosphere, it can approach temperatures as low as -110°F (-79°C), making it denser than the surrounding air. This greater density allows CO₂ to replace the oxygen above burning surfaces, maintaining a smothering atmosphere and effectively suppressing the fire.

Physiological Effects of Carbon Dioxide

Carbon dioxide is a natural component of Earth's atmosphere, typically present at 0.04%. It is also a normal by-product of cellular respiration in both humans and animals. In the human body, CO₂ plays a crucial role in regulating breathing, ensuring a sufficient supply of oxygen to the system.

© 2024 Knowledge on Carbon Dioxide Properties. All rights reserved.

Storage of Liquid Carbon Dioxide

Which of the following statements about the storage of liquid carbon dioxide is correct?

High-pressure cylinders typically have a capacity ranging from 750 lb (340 kg) to 60 tons (54,431 kg).
Low-pressure storage units are designed to maintain a storage temperature near 0°F (-18°C).
High-pressure cylinders do not require siphon tubes for discharge.
The discharge of carbon dioxide from storage cylinders has a white, cloudy appearance due to water fog.

CFPS QUIZ "Comprehensive Quiz on the Properties and Safety of Carbon Dioxide as a Fire-Extinguishing Agent

Quiz on Carbon Dioxide Properties as a Fire-Extinguishing Agent

Carbon dioxide (CO₂) is an effective fire-extinguishing agent due to its various properties. It is non-combustible, does not react with most substances, and provides its own pressure for discharge. As a gas, CO₂ can easily penetrate fire areas and is capable of suppressing flames by displacing oxygen. It is safe to use on energized electrical equipment as it does not conduct electricity. Additionally, it leaves no residue, eliminating the need for cleanup. CO₂ has unique thermodynamic properties. At room temperature and pressure, it is a colorless and odorless gas. It can be easily liquefied by compressing and cooling, and further compression and cooling can turn it into a solid. Its pressure and temperature influence its state (gas, liquid, or solid), with transitions occurring at critical points, including the triple point.

Multiple-Choice Questions

1. Which of the following properties makes carbon dioxide an effective fire-extinguishing agent?

• a) It reacts with most substances.
• b) It can conduct electricity and is safe for electrical equipment.
• c) It leaves no residue after use.
• d) It requires an external source of pressure for discharge.

Answer: c) It leaves no residue after use.

2. What state does carbon dioxide exist in above the critical temperature of 87.8°F (31°C)?

• a) Solid
• b) Liquid
• c) Gas
• d) Gas and liquid

Answer: c) Gas

3. At what temperature does carbon dioxide exist in all three phases (gas, liquid, and solid) simultaneously?

• a) -69.9°F (-57°C)
• b) 0°F (-18°C)
• c) 87.8°F (31°C)
• d) 75 psia (517 kPa)

Answer: a) -69.9°F (-57°C)

4. What happens to liquid carbon dioxide when it is discharged into the atmosphere?

• a) It remains as a liquid and evaporates slowly.
• b) It instantly flashes to vapor and a portion becomes dry ice (snow).
• c) It freezes into solid dry ice immediately.
• d) It solidifies into a compact block.

Answer: b) It instantly flashes to vapor and a portion becomes dry ice (snow).

5. What is a critical safety measure when discharging carbon dioxide?

• a) The discharge nozzles should be insulated.
• b) The nozzles must be grounded to prevent static electricity buildup.
• c) The system should be pressurized with air.
• d) Discharge should be performed in an open area to avoid contamination.

Answer: b) The nozzles must be grounded to prevent static electricity buildup.

6. What happens to the density of carbon dioxide vapor when it is discharged at very low temperatures?

• a) It becomes lighter than air and rises.
• b) It maintains the same density as the surrounding air.
• c) It becomes much denser than air and sinks.
• d) It disperses evenly in the atmosphere.

Answer: c) It becomes much denser than air and sinks.

7. What is the standard storage temperature for low-pressure carbon dioxide containers?

• a) 87.8°F (31°C)
• b) 0°F (-18°C)
• c) -69.9°F (-57°C)
• d) 70°F (21°C)

Answer: b) 0°F (-18°C)

© 2024 Fire Safety Knowledge Quiz. All rights reserved.

CFPA EXAM :Fire Pump Installation Quiz: Test Your Knowledge on Power Supplies and Standards

Fire Pump Installation Quiz

1. Among acceptable power supplies for fire pumps, which can be used as a stand-alone power source without a backup?

• a) Battery backup system
• b) Solar panels
• c) Reliable utility service
• d) Hybrid power system

Answer: c) Reliable utility service

2. According to NFPA 70, Article 100, a service begins where the utility wiring stops. This point is referred to as the:

• a) Service disconnect
• b) Service point
• c) Load center
• d) Circuit breaker

Answer: b) Service point

3. For fire pump installations, electrical power should ideally be provided through:

• a) A shared circuit with other equipment
• b) A battery backup system
• c) A dedicated circuit to the fire pump controller
• d) A general-purpose extension cord

Answer: c) A dedicated circuit to the fire pump controller

4. The service equipment for fire pump installations should be located to:

• a) Increase power efficiency
• b) Minimize the possibility of damage by fire
• c) Allow easy access for maintenance
• d) Support multiple electrical loads

Answer: b) Minimize the possibility of damage by fire

5. On-site electrical power production includes:

• a) Utility-provided power
• b) Renewable energy from off-site sources
• c) Prime movers and generators located on the premises
• d) Electrical power purchased from third-party vendors

Answer: c) Prime movers and generators located on the premises

6. What is the primary role of on-site generation in fire pump installations?

• a) To supplement utility power during peak hours
• b) To supply all electrical loads in the facility
• c) To reduce energy costs
• d) To ensure compliance with NFPA 70

Answer: b) To supply all electrical loads in the facility

7. What is the connection method for electrical power when a dedicated service is not possible for fire pump installations?

• a) Tap ahead of the service disconnect
• b) Shared connection with general building circuits
• c) Connection via an extension cord
• d) Integration with solar inverters

Answer: a) Tap ahead of the service disconnect

NEC 314.27 Outlet Box Requirements for Luminaires and Ceiling Fans

Understanding NEC 314.27: Requirements for Outlet Boxes

The NEC 314.27 outlines the standards and requirements for outlet boxes used to support electrical fixtures like luminaires, ceiling fans, and other utilization equipment. These regulations ensure that the outlet boxes are adequately rated for the weight and installation of electrical equipment, preventing potential hazards such as equipment failure or electrical fires.

A) Boxes at Luminaire or Lampholder Outlets

• Vertical Surface Outlets: Outlet boxes must be marked with the maximum weight they can support if different from 23 kg (50 lb).
• Exception: Luminaires or lampholders that weigh no more than 3 kg (6 lb) can be mounted on other boxes, provided they are securely fastened with at least two screws.
• Ceiling Outlets: The box must support a luminaire weighing a minimum of 23 kg (50 lb). If the luminaire weighs more, it must be independently supported unless the outlet box is rated for the additional weight.

B) Floor Boxes

Floor boxes used for receptacles must be specifically listed for this application. If located in elevated floors of show windows or similar locations, the authority having jurisdiction may permit other boxes as long as they are not exposed to physical damage, moisture, or dirt.

Exception: In some cases, receptacles and covers in elevated floors may use boxes that are not listed for floor applications, provided they are not exposed to damage.

C) Boxes at Ceiling-Suspended (Paddle) Fan Outlets

• Ceiling-Fan Boxes: The outlet boxes must be listed for ceiling fans and marked by the manufacturer to indicate their suitability for this purpose. The maximum weight supported is 32 kg (70 lb).
• For heavier fans: If the ceiling fan weighs more than 16 kg (35 lb), the box must include a weight limit marking.

D) Utilization Equipment

Boxes supporting other equipment must meet the same weight requirements as those supporting luminaires of similar size and weight.

Exception: Equipment weighing no more than 3 kg (6 lb) can be mounted on other boxes or plaster rings, as long as they are secured with at least two screws.

E) Separable Attachment Fittings

Outlet boxes may also support listed locking support and mounting receptacles used with compatible attachment fittings. These must be identified for use within specific weight and mounting orientation limits. When a supporting receptacle is installed within a box, it must be included in the fill calculation for box size.

Key Takeaways

The guidelines in NEC 314.27 are essential for maintaining safe electrical installations. Ensuring that outlet boxes are correctly rated and marked according to the weight and type of equipment they will support can help avoid electrical failures, fires, and other hazards. Always ensure you choose the correct outlet box based on the manufacturer’s specifications to ensure safety and compliance with NEC regulations.

These requirements help ensure long-term safety and performance in residential, commercial, and industrial electrical systems.

© 2024 NEC Electrical Installations. All Rights Reserved.

Understanding NEC 408.4: Proper Circuit Identification for Electrical Safety and Compliance"

Understanding NEC 408.4: Importance of Proper Circuit Identification for Electrical Safety

Proper circuit identification is essential for ensuring safety, efficiency, and compliance in electrical installations. In this article, we will explore NEC 408.4, which outlines the importance of clear circuit identification in electrical systems. Whether you're an electrician, contractor, or homeowner, understanding these requirements can help avoid costly mistakes and improve the safety of your electrical system.

A) Circuit Directory or Circuit Identification

According to NEC 408.4, proper circuit identification is a critical aspect of electrical systems. Here’s why:

• Clear and Specific Identification: Every circuit, including modifications, must have a clear label indicating its purpose. This helps prevent confusion during installation, maintenance, or troubleshooting.
• Unused Circuits: Spare positions with unused overcurrent devices or switches must be labeled accordingly, ensuring clarity even for future use.
• Panel Directory: A circuit directory must be placed visibly inside the panelboard or near each switch or circuit breaker. This ensures electricians and technicians can quickly identify circuits without wasting time.
• Avoiding Temporary Descriptions: It’s important that circuit descriptions are permanent and do not rely on transient or temporary conditions, such as occupancy.

B) Source of Supply

NEC 408.4 also requires that the power source for electrical devices and equipment be clearly marked:

• Permanent Marking: For switchboards, panelboards, and switchgear, the power source must be permanently marked, especially if supplied by feeders in non-residential settings. This labeling helps ensure proper maintenance and troubleshooting.
• Durability of Labels: Labels must be durable enough to withstand the environment. Avoid handwritten labels, as they can fade or become illegible over time.

Why Proper Circuit Identification Matters

Proper identification of circuits plays a vital role in electrical safety. It allows electricians, maintenance teams, and emergency responders to work efficiently and safely. It’s also essential for preventing errors during repairs, upgrades, or emergency interventions.

By adhering to NEC 408.4 guidelines, you create a more organized and secure electrical system, making it easier to troubleshoot, maintain, and enhance the system in the future.

Spaces About Electrical Equipment.

Requirements for Working Spaces Around Electrical Equipment (NEC 110.26)

This section specifies the requirements for working spaces around electrical equipment operating at 1000 volts or less, ensuring safe operation and maintenance.

General Requirements

• Working spaces must always be maintained around electrical equipment for safe operation and maintenance.
• These requirements apply to equipment likely to require examination, adjustment, or servicing while energized.

(A) Working Space

This subsection defines the dimensions of working spaces required around electrical equipment. Details are as follows:

(1) Depth of Working Space

The depth required depends on the voltage and conditions around the equipment, as outlined in the table below:

Nominal Voltage to Ground	Condition 1	Condition 2	Condition 3
0-150	900 mm (3 ft)	900 mm (3 ft)	900 mm (3 ft)
151-600	900 mm (3 ft)	1.0 m (3 ft 6 in)	1.2 m (4 ft)
601-1000	900 mm (3 ft)	1.2 m (4 ft)	1.5 m (5 ft)

Notes on Depth:

• Dead-Front Assemblies: No rear/side working space is required if all maintenance is done from the front.
• Low Voltage: Smaller working spaces are allowed for live parts ≤30V RMS, ≤42V peak, or ≤60V DC.
• Existing Buildings: Reduced clearance is permitted with written maintenance procedures.

(2) Width of Working Space

The width must be at least 762 mm (30 in.) or the width of the equipment, whichever is greater, and must allow doors/panels to open at least 90 degrees.

(3) Height of Working Space

• Working space must extend from the floor to 2.0 m (6.5 ft) or the height of the equipment, whichever is greater.
• Equipment associated with the installation may protrude up to 150 mm (6 in.) beyond the front.
• Exceptions:
  • Panels ≤200A in existing dwellings.
  • Meters installed in meter sockets.
  • Open battery racks follow 480.10(D) clearance requirements.

(4) Limited Access

When equipment is installed in spaces with limited access:

• Ceiling openings must be at least 559 mm × 559 mm (22 in. × 22 in.), or crawl space openings must be 559 mm × 762 mm (22 in. × 30 in.).
• Working space width must be at least 762 mm (30 in.) or the width of the equipment, whichever is greater.
• Doors/panels must open at least 90 degrees.
• Depth must follow the requirements in the table above.

Interior Exit Stairways And Ramps Enclosures Fire Resistance.

Interior Exit Stairways And Ramps Enclosures.

Interior Exit Stairways And Ramps Enclosures . must be constructed as fire barriers according to Section 707 of the IBC, or as horizontal assemblies according to Section 711 IBC , or both.

Fire-Resistance Rating of Enclosures for interior exit stairways and ramps

1. Not less than 2 hours if connecting four stories or more.
2. Not less than 1 hour if connecting less than four stories.

Termination. 

Interior exit stairways and ramps shall terminate at an exit discharge or a public way.

Note:

1. The number of stories includes any basements but excludes mezzanines. The fire-resistance rating of the interior exit stairways and ramps should not be less than the floor assembly being penetrated, but it doesn't need to exceed 2 hours.
2. If a stairway or ramp does extend below the level of exit discharge, it must be equipped with an approved barrier at the exit discharge level. This barrier serves to prevent people from inadvertently continuing their descent into lower levels of the building.

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CFPS Exam Question Example (Fire pump suction under a positive pressure )

CFPS Exam Question Example ( Gravity tanks )

 

Q: What type of supply is considered acceptable as a single supply and is often made up of gravity tanks with adequate capacity and elevation?

 

a)       Secondary supply

b)      Cross-connected supply

c)       Dual supply system

d)      Primary supply

 Answer: D) Primary supply

FIRE PROTECTION HANDBOOK

15-64 SECTION 15 ■ Water Supplies for Fixed Fire Protection

Gravity Tanks

Gravity tanks of adequate capacity and elevation make a good primary supply and may be acceptable as a single supply.

CFPS Exam Question Example ( Size Of Street Mains supply )

Q:  What is the usual diameter considered inadequate and unreliable for street mains in the context of fire protection water supply?

 

a)       Less than 6 inches (152 mm)

b)      Less than 4 inches (102 mm)

c)       Less than 8 inches (203 mm)

d)      Less than 10 inches (254 mm)

 

Answer: A) Less than 6 inches (152 mm)

FIRE PROTECTION HANDBOOK

15-64 SECTION 15 ■ Water Supplies for Fixed Fire Protection

The size and arrangement of street mains and feeders from public water supplies are also important. Connections from large mains fed two ways or from two mains on a grid system may provide an excellent supply. Street mains less than 6 in. (152 mm) in diameter are usually considered inadequate and unreliable. Feeds from dead-end mains are also undesirable

IBC & SBC : Fire wall protection in Stepped buildings

Fire wall protection in Stepped buildings

1. Stepped buildings: This refers to buildings with different roof levels separated by a fire wall.

2- Termination of Fire Wall: If a fire wall also acts as an exterior wall for a building and separates buildings with different roof levels, it must terminate at least 30 inches (762 mm) above the lower roof level.

3. Fire resistance rating: the exterior wall for a height of 4.5 m above the lower roof is not less than 1-hour fire-resistance-rated construction from both sides with openings protected by fire assemblies having a fire protection rating of not less than ¾ hour.

4. Exception: There's an exception to the termination height requirement. If the fire wall terminates at the underside of the roof sheathing, deck, or slab of the lower roof, certain conditions must be met:

1. The lower roof assembly within 3.0 meters of the wall must have a fire-resistance rating of at least one hour.
2.  The supporting elements (such as beams or columns) for the rated roof assembly must have a fire-resistance rating of at least one hour for their entire length and span.
3. Openings in the lower roof must not be located within 3 meters of the fire wall.

These regulations aim to ensure that in buildings with different roof levels, fire containment and resistance are maintained adequately to prevent the spread of fire between sections or buildings.

CFPS Exam Question Example -operating principles can be used in a gas-sensing fire detector

 

 

CFPS Exam Question Example 

 Which operating principles can be used in a gas-sensing fire detector or a combination (multisensor) detector ?

A)      Semiconductor, catalytic element, or infrared absorption.

B)      Spot type, beam type, or air sampling type.

C)      Heat type, ionization type, or dual-sensor type.

D)      Optical type, thermal type, or particle type.

 

Answer: A) Semiconductor, catalytic element, or infrared absorption.

Section 14 

CHAPTER 2 ■ Automatic Fire Detectors 14-23

GAS-SENSING FIRE DETECTORS

Many changes occur in the gas content of the environment during a fire. It has been observed that detectable levels of gases are reached after detectable smoke levels and before detectable heat levels. One of three operating principles, that is, semiconductor, catalytic element, or infrared absorption, may be used in a gas-sensing fire detector or in a combination (multisensor) detector.

 

CFPS Exam Question Example : Which types of detectors are used to sense radiant energy emitted from combustion reactions?

CFPS Exam Question Example 

    Which types of detectors are used to sense radiant energy emitted from combustion reactions?

 

A)      Flame detectors and spark/ember detectors

B)      Smoke detectors and heat detectors

C)      Carbon monoxide detectors and gas detectors

D)      Motion detectors and occupancy sensors

 

Answer: A) Flame detectors and spark/ember detectors

----------------

Section 14

CHAPTER 2 ■ Automatic Fire Detectors 14-23

RADIANT ENERGY–SENSING FIRE DETECTORS.

Radiant energy–sensing devices sense the radiant energy (electromagnetic radiation) emitted as a by-product of the combustion reaction, which obeys the laws of optics. This includes radiation in the ultraviolet, visible, and infrared portions of the spectrum, emitted by flames or glowing embers. They are categorized as flame detectors and spark/ember detectors.

CFPS Exam Example question - Which of the following statements is true about UV detectors used for fire detection?

 

CFPS Exam Question Example 

Which of the following statements is true about UV detectors used for fire detection?

A) UV detectors are not sensitive to hydrocarbons or metals.

B)  UV detectors are sensitive to all types of fires except hydrocarbons.

C) UV detectors are sensitive to most fires, including hydrocarbons, ammonia, sulfur, hydrogen, hydrazine, and metals

D) UV detectors are not effective in detecting fires caused by middle and heavy fraction petroleum distillates.

Answer: c) UV detectors are sensitive to most fires, including hydrocarbons, ammonia, sulfur, hydrogen, hydrazine, and metals.

SECTION 14 

14-24 SECTION 14 ■ Detection and Alarm

Flame Detectors.

Ultraviolet Flame Detectors. 

The ultraviolet spectrum comprises wavelengths ranging from approximately 0.1µm to 0.35µm.  UV detectors typically use a vacuum photodiode Geiger-Muller tube to detect the ultraviolet radiation that is produced by a flame. The photodiode allows a burst of current to flow for each UV photon that hits the active area of the tube. When the number of current bursts per unit time reaches a set level, the detector initiates an alarm. A special control unit is required to monitor the count rates from UV detectors and initiate alarm.

UV detectors are sensitive to most fires, including hydrocarbons (liquids, gases, and solids), ammonia, sulfur, hydrogen, hydrazine, and metals such as magnesium. However, the smoke produced by combustion of middle and heavy fraction petroleum distillates is highly absorptive in the UV end of the spectrum, and this must be compensated for in system design if UV detectors are used

 

جدار الحريق فى الاسقف المائلة

جدران الحريق فى الاسقف المائلة

لضمان تحقيق الهدف من جدران الحريق يجب تحقيق بعض الشروط فى الاسقف المائلة مع بعض المتطلبات.

المتطلبات :

عندما تكون السقف من جهة واحدة أو كلا الجهتين لجدار الحريق مائلة نحو الجدار الحريق بميل يتجاوز 2 وحدة عمودية في 12 وحدة أفقية (2:12)، فيجب تحقيق بعض المتطلبات و هى تمديد جدار الحريق.

تمديد جدار الحريق بالطريقة التالية :

قياس ارتفاع السقف الموجود على بعد 1200 مم (1.2 متر) من جدار الحريق. إضافة 750 مم (0.75 متر) إلى هذا الارتفاع. يجب أن يمتد جدار الحريق إلى هذا الارتفاع المحسوب. ومع ذلك، إذا أسفر هذا الحساب عن ارتفاع أقل من 750 مم، فإن جدار الحريق يجب أن يمتد على الأقل إلى ارتفاع 750 مم.

المرجع:
1- الكود السعودى 201 : 706.6.2 Buildings with sloped roofs

Requirements for Fire Wall Extension in Buildings with Sloped Roofs

Introduction

Fire Wall Extension in Buildings with Sloped Roofs.

Requirement :

When the roof on one side or both sides of the fire wall slopes towards the fire wall at a slope greater than 2 units vertical in 12 units horizontal (2:12), certain requirements need to be met.

Extension of the Fire Wall

The fire wall needs to extend to a certain height to effectively contain a potential fire. This height is calculated as follows:

1.    Measure the height of the roof located (4 ft.) 1200 mm (1.2 meters) from the fire wall.
2.   Add (30 in.)750 mm (0.75 meters) to this height.
3.  The fire wall should extend to this calculated height.
4.  However, if this calculation results in a height less than (30 in.)750 mm, then the fire wall should still extend to a minimum height of (30 in.) 750 mm.

In essence, the regulation ensures that the fire wall extends to a sufficient height to properly contain any fire that might occur in buildings with sloped roofs, based on the slope of the roof and its proximity to the fire wall.

Reference :

2021 International Building Code (IBC)-706.6.2Buildings with sloped roofs.

SBC 201-2018: 706.6.2 Buildings with sloped roofs