CFPS Questions and Answers

Aqueous film-forming agents (AFFF) are synthetic foam concentrates that can be proportioned into final concentrations of 1%, 3%, and 6%, depending on the type of fuel and application method12. AFFF forms a thin aqueous film on the surface of the flammable liquid, which prevents vapor release and provides rapid fire knockdown and extinguishment3. AFFF is suitable for Class B fires involving hydrocarbon fuels such as gasoline, diesel, kerosene, etc. References:

• Fire Fighting Foams - Chemguard
• Extinguishing foam: types, operation and application areas
• [NFPA 11: Standard for Low-, Medium-, and High-Expansion Foam]

0.62

The discharge coefficient of a solid stream nozzle for a standard orifice with sharp edges is a dimensionless number that indicates the ratio of the actual flow rate to the theoretical flow rate of the nozzle. The discharge coefficient depends on the geometry and the flow conditions of the nozzle. According to the web search results, the typical discharge coefficient of a solid stream nozzle for a standard orifice with sharp edges is about 0.62, which means that the actual flow rate is about 62% of the theoretical flow rate.This value is based on the experiments conducted by the National Bureau of Standards (now NIST) and reported in the paper “Discharge Coefficients of Fire Nozzles”1.The paper also provides a formula to calculate the discharge coefficient for different nozzle diameters and pressures123

Fire pump

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A multistage centrifugal fire pump is defined as having two or more impellers on one shaft as a single unit. A multistage centrifugal pump is a type of centrifugal pump that uses multiple impellers to increase the pressure and flow of water.Each impeller acts like a single-stage pump within a chain of pumps, and the water passes through each impeller in series, gaining pressure and velocity at each stage1.A multistage centrifugal fire pump is used to provide high-pressure water for fire protection systems, especially in high-rise buildings or large industrial facilities2.A multistage centrifugal fire pump can be driven by an electric motor, a diesel engine, or a steam turbine3.References:

• Our Guide to Multistage Centrifugal Pumps | C&B Equipment
• Fire Pump Types | NFPA
• NFPA 20: Changes to the fire pump standard - Consulting

The removal of flammable vapors by displacement for cleaning a storage tank can be accomplished by displacement with air, inert gas, and water. Water is a common method of displacing flammable vapors from tanks, as it is readily available, inexpensive, and non-reactive with most fuels. Water can be sprayed into the tank to create a water seal that prevents the vapors from escaping and reduces the oxygen concentration in the tank. Water can also be used to rinse the tank walls and remove any residual fuel. However, water displacement may not be suitable for some tanks that contain water-sensitive or water-soluble fuels, or for tanks that have limited drainage or disposal facilities.

References:ust permanent closure requirements - Nevada;A Guide to Safety in Confined Spaces - CDC Stacks;Fire Explosion Prevention – Visual Encyclopedia of Chemical Engineering …

Cellulose nitrate products begin to decompose at about 300 °F (150 °C). This is the temperature at which the nitrate ester bonds start to break down and release nitric acid, which further catalyzes the decomposition. The decomposition temperature depends on the nitrogen content, the stabilizers, and the external heating rate of the cellulose nitrate. Higher nitrogen content, lower stabilizer concentration, and faster heating rate lower the decomposition temperature and increase the risk of thermal runaway.

References:Nitrocellulose - Wikipedia;Comparative analysis of stable decomposition and combustion kinetics of nitrated cellulose;Degradation of aged nitrocellulose investigated by thermal analysis methods;Nitrocellulose;Effect of stabilizers and nitrogen content on thermal properties of nitrocellulose

Critical radiant flux is used to classifyinterior floor finishes. Critical radiant flux is a measure of the minimum radiant heat energy required to sustain flame propagation on a floor material or covering. It is determined by exposing a specimen to a radiant heat gradient and observing the distance from the ignition point to the flame-out point.The shorter the distance, the higher the critical radiant flux and the better the fire performance of the floor material or covering1.Critical radiant flux is used to classify floor materials and coverings according to their fire hazard and resistance, and to specify the minimum requirements for different occupancies and applications2.For example, the International Building Code (IBC) requires that interior floor finishes and coverings in exit access corridors and exit enclosures have a critical radiant flux of not less than 0.45 W/cm2, while those in other spaces have a critical radiant flux of not less than 0.22 W/cm23.Critical radiant flux is also used to evaluate the fire safety of floor materials and coverings in transportation vehicles, such as aircraft, trains, and buses4.

OSHA regulation 1910.110 addresses storage and handling of liquefied petroleum gas (LPG). This regulation covers the general requirements for the design, construction, installation, operation, inspection, and maintenance of LPG systems, including containers, piping, valves, fittings, regulators, burners, and appliances. The regulation also specifies the safety precautions and procedures for the prevention of fire and explosion hazards involving LPG. The regulation applies to all employers who store, handle, or use LPG in their workplaces.References:

• OSHA: 1910.110 - Storage and handling of liquefied petroleum gases1
• Nebula Safety: Storage & Handling of Liquefied Petroleum Gases (LPGs)2

According to the web search results, 79% of fire departments surveyed participate in the delivery of emergency medical services (EMS).This is based on the NFPA report “US Fire Department Profile 2020”1, which states that nationwide, 37% of fire departments provided no EMS, 46% provided basic life support (BLS), and 17% provided advanced life support (ALS). Therefore, the percentage of fire departments that provided either BLS or ALS is 46% + 17% = 63%. However, this does not include fire departments that provided EMS through a third-party contract or agreement.According to the NFPA fire service survey from 2018–20202, 16% of fire departments reported having such an arrangement. Therefore, the percentage of fire departments that participated in the delivery of EMS in some form is 63% + 16% = 79%.References:

• NFPA report - U.S.fire department profile3
• US Fire Department Profile 2020 Supporting Tables2

The two classes of fire models arephysical and mathematical. Physical fire models are scaled-down representations of real fire scenarios, using laboratory experiments and measurements to study the fire behavior and effects.Physical fire models can be used to test hypotheses, validate mathematical models, and provide empirical data for fire analysis1. Mathematical fire models are numerical or analytical solutions of the equations that govern the fire phenomena, such as heat transfer, fluid dynamics, combustion, and chemical kinetics.Mathematical fire models can be used to simulate fire scenarios, predict fire outcomes, and optimize fire protection systems2. There are two major categories of mathematical fire models: zone models and field models. Zone models divide the fire compartment into two or more homogeneous zones, such as upper and lower layers, and apply mass and energy conservation equations to each zone.Zone models are relatively simple, fast, and easy to use, but they have limitations in accuracy and applicability3. Field models solve the partial differential equations that describe the fire-driven fluid flow and heat transfer in three dimensions, using computational fluid dynamics (CFD) techniques.Field models are more detailed, realistic, and flexible, but they require more computational resources and expertise4.References:

• Fire modelling with Computational Fluid Dynamics - BRE Group
• Fire modeling programs | NIST
• interFIRE, A site dedicated to improving fire investigation worldwide.
• Computer Fire Models for Fire Investigation and Reconstruction

The maximum discharge time permitted for halocarbon clean agent systems is10 seconds. This is the requirement of NFPA 2001, which is the standard for clean agent fire extinguishing systems.NFPA 2001 states that the discharge time for halocarbon agents shall not exceed 10 seconds, unless otherwise permitted by the authority having jurisdiction1. Halocarbon agents are synthetic compounds that contain carbon, fluorine, and sometimes other elements, such as hydrogen, chlorine, or bromine.Examples of halocarbon agents include HFC-227ea, HFC-125, and FK-5-1-122. Halocarbon agents work by absorbing heat and interrupting the chemical chain reaction of the fire.They are electrically nonconductive and leave no residue upon evaporation3.Halocarbon agents are suitable for protecting Class A, B, and C fires involving electrical equipment, flammable liquids, and ordinary combustibles4. The discharge time is the time required to release the agent from the storage containers to the protected enclosure.A short discharge time is important to achieve the design concentration of the agent before the fire grows or spreads5.References:

• NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems
• Clean Agent System Basics | NFPA
• Fire Fighting Foams - Chemguard
• Clean Agent Fire Suppression Systems | Fike
• Category | Rotarex Firetec

Fire extinguisher

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smothering.

The primary mechanism by which carbon dioxide extinguishes fire is smothering, or displacing the oxygen that the fire needs to sustain combustion. Carbon dioxide is a gas that is heavier than air, so when it is released from the extinguisher, it forms a blanket over the fire and pushes away the oxygen.Without oxygen, the fire cannot continue to burn and is extinguished1234

Cooling is a secondary mechanism by which carbon dioxide extinguishes fire. Carbon dioxide is stored as a liquid under high pressure in the extinguisher, and when it is released, it expands rapidly and cools down. The cold gas absorbs heat from the fire and lowers the temperature of the fuel below its ignition point.However, cooling is not the main effect of carbon dioxide, as it is less effective than water in reducing the heat of the fire1234

Saponification and chemical inhibition are not mechanisms by which carbon dioxide extinguishes fire. Saponification is a process by which wet chemical agents react with fats and oils to form a soapy foam that seals the surface of the fire and prevents re-ignition. Chemical inhibition is a process by which dry chemical agents interfere with the chemical chain reaction of the fire and stop the production of free radicals that propagate the combustion.These mechanisms are used by other types of fire extinguishers, such as Class K and Class D extinguishers, respectively1234

References:

• Carbon Dioxide Extinguishers - University of South Carolina4
• How Does A Co2 Fire Extinguisher Work2
• Why is Carbon Dioxide Used to Extinguish Oil Fires3
• What is a Carbon Dioxide Fire Extinguisher?- Safeopedia1

Potassium bicarbonate is a dry chemical agent that is considered to be twice as effective as sodium bicarbonate in fire suppression, especially for Class B fires involving flammable liquids and gases. This is because potassium bicarbonate has a higher melting point and a lower decomposition temperature than sodium bicarbonate, which allows it to form a more stable and insulating layer on the burning surface.Potassium bicarbonate also has a lower pH and a higher specific gravity than sodium bicarbonate, which enhances its penetration and dispersion abilities123.References:Dry Chemical Agents - Purple-K Powder is Purple - Chemguard;Evaluation of Dry Chemical Fire Extinguishing Standards - NFPA;Potassium bicarbonate - Wikipedia.

valve at the inspector’s test connection.

For wet-pipe automatic sprinkler systems, the only proper way to test the operation of a vane-type water flow alarm initiating device is to open the valve at the inspector’s test connection. This is a small valve that is located at the end of a pipe that is connected to the sprinkler system, usually at the most remote or highest point. The inspector’s test connection simulates the flow of a single sprinkler head and activates the vane-type water flow switch, which in turn triggers the fire alarm panel and the external alarm devices.Opening the valve at the inspector’s test connection also allows the water to drain from the system, preventing corrosion and freezing1234

Opening the main (2 in. diameter) drain is not a proper way to test the operation of a vane-type water flow alarm initiating device, because it does not create enough flow to activate the switch. The main drain is used to drain the entire sprinkler system for maintenance or repair purposes, and it is usually located at the main riser or the fire department connection.Opening the main drain may also cause a pressure drop in the system, which could affect the performance of the sprinklers1234

Opening the alarm test by-pass valve at the system’s main riser is not a proper way to test the operation of a vane-type water flow alarm initiating device, because it does not simulate the actual flow of a sprinkler head. The alarm test by-pass valve is used to test the operation of the external alarm devices, such as the water motor gong or the electric bell, without activating the fire alarm panel. The alarm test by-pass valve is usually located near the alarm check valve or the water flow switch, and it allows water to flow through a small orifice to the alarm devices.Opening the alarm test by-pass valve does not create enough flow to activate the vane-type water flow switch1234

Opening the check valve from the city connection is not a proper way to test the operation of a vane-type water flow alarm initiating device, because it does not create any flow in the sprinkler system. The check valve from the city connection is used to prevent the backflow of water from the sprinkler system to the city water supply, and it is usually located at the fire department connection or the main riser.Opening the check valve from the city connection does not affect the water flow in the sprinkler system, and it does not activate the vane-type water flow switch1234

References:

• Fire Sprinkler Flow Switch & Tamper Switch Inspection & Maintenance3
• Sprinkler System Water Flow Device Testing - ORR Protection2
• VSR-AT Auto-Test Waterflow Alarm Switch | Potter Electric4
• WFDNA Series Vane-type Waterflow Detectors - Steel Fire Equipment5

The minimum pipe diameter size for direct discharge of steam inside a water tank is 2 in. (50 mm), according to NFPA 13, Standard for the Installation of Sprinkler Systems. This is to prevent water hammer, noise, and vibration caused by the rapid condensation of steam when it contacts the water. The pipe should also be equipped with a check valve to prevent backflow of water into the steam source.References: NFPA 13, Standard for the Installation of Sprinkler Systems, 2023 Edition, Chapter 8, Section 8.16.4.5.3; NFPA Fire Protection Handbook, 21st Edition, Chapter 14, Section 14.3.4.2.

According to the web search results, 79% of fire departments surveyed participate in the delivery of emergency medical services (EMS).This is based on the NFPA report “US Fire Department Profile 2020”1, which states that nationwide, 37% of fire departments provided no EMS, 46% provided basic life support (BLS), and 17% provided advanced life support (ALS). Therefore, the percentage of fire departments that provided either BLS or ALS is 46% + 17% = 63%. However, this does not include fire departments that provided EMS through a third-party contract or agreement.According to the NFPA fireservice survey from 2018–20202, 16% of fire departments reported having such an arrangement. Therefore, the percentage of fire departments that participated in the delivery of EMS in some form is 63% + 16% = 79%.References:

• NFPA report - U.S.fire department profile3
• US Fire Department Profile 2020 Supporting Tables2

According to NFPA 400, Table 5.2.1.1.3, the maximum allowable quantity (MAQ) of a nonliquified oxidizing gas per control area in an unsprinklered area is 2000 ft3 (56 m3) when stored in a gas cabinet. This quantity can be increased by 100% if the area is sprinklered or by 300% if the area is also provided with a gas detection system. A gas cabinet is a ventilated enclosure for the storage of one or more compressed gas containers that provides a method of control for potential leakage or fire exposure hazards [NFPA 400, 3.3.32].References:NFPA 400, Table 5.2.1.1.3;NFPA 400, 3.3.32;NFPA 400, 5.2.1.1.3.1;NFPA 400, 5.2.1.1.3.2.

Computers and other information technology equipment are particularly susceptible to heat, steam, and combustion products, which can damage their sensitive components, cause data loss or corruption, and impair their functionality.Therefore, fire protection for IT equipment should consider the potential sources of heat, steam, and combustion products, such as electrical faults, flammable liquids, dust accumulation, water-based sprinklers, or smoke from adjacent areas, and implement appropriate measures to prevent, detect, and suppress fires, as well as to minimize the exposure of IT equipment to these hazards1234.References:Standard for the Fire Protection of Information Technology Equipment;Fire Protection of Computer Rooms—Legal Obligations and Best Practices - ISACA;Exploring Requirements for Information Technology Equipment;Demystifying IT room protection requirements - Consulting.

Smoke purging, smoke removal, smoke exhaust, or smoke extraction are different terms for the same type of smoke management method, which is airflow. Airflow is the method of controlling smoke by creating a flow of air that either pushes or pulls the smoke away from the desired areas. Airflow can be achieved by natural or mechanical means, such as vents, fans, or dampers. Airflow can also be used to create a smoke layer above the occupant level in large spaces, such as atriums or warehouses, by exhausting the hot smoke and supplying fresh air below the layer.References:Smoke Extraction System - NAFFCO Smoke Management;Post-Fire Smoke Purge Systems: When Are They Required? - NY Engineers; NFPA Fire Protection Handbook, 21st Edition, Chapter 9, Section 9.2.1.

According to NFPA 13, Table 17.4.2.1 (a), the maximum distance between hangers for an automatic fire sprinkler system for a threaded lightwall steel pipe of 2 in. diameter is 10 ft. This is done to ensure that there are not long stretches of unsecured piping that could sag, leak, or break. The distance between hangers may vary depending on the type of pipe, the type of hanger, and the seismic design category of the building.References:NFPA 13, Table 17.4.2.1 (a);Hangers and Support of Sprinkler System Piping | NFPA | NFPA.

Large quantities of flammable or combustible liquids (all classes) are best transferred through piping by pumps. This method minimizes the risk of spills, leaks, fires, and explosions that may occur when transferring liquids by other means, such as air pressure, inert gas pressure, or gravity flow. Piping systems should be designed, installed, operated, and maintained in accordance with NFPA 30: Flammable and Combustible Liquids Code and other applicable standards. Piping systems should also include proper grounding and bonding, venting, and emergency shutoff devices to prevent static electricity, overpressure, and accidental release of liquids.

References: NFPA 30: Flammable and Combustible Liquids Code, 2021 Edition, Chapter 271; Fire Protection Handbook, 20th Edition, Volume 1, Chapter 8, Section 8.3.12.

25%

Explosions or fires from flammable gas or oil fuel vapor-air mixtures may be prevented by ventilation and controls that keep the flammable vapor content below 25% of the lower flammable limit (LFL) of the vapor-air mixture, according to the web search results. The LFL is the lowest concentration of a gas or vapor in air that can produce a flash of fire in the presence of an ignition source. Below the LFL, the mixture is too lean to burn. The LFL varies for different gases and vapors, and it is usually expressed as a percentage by volume of air at 25°C and atmospheric pressure. For example, the LFL of methane is 4.4%, which means that a mixture of methane and air with less than 4.4% methane cannot ignite. To prevent explosions or fires, the concentration of flammable gases or vapors should be kept below 25% of their LFL, which is equivalent to 1.1% methane in this case. Ventilation, natural or mechanical, is one of the methods to achieve this by diluting the flammable gases or vapors with fresh air.Controls, such as gas detectors, alarms, valves, and interlocks, are another method to monitor and regulate the flammable gas or vapor levels and prevent them from reaching dangerous concentrations1234

The correct answer is C. A thermocouple is a temperature measurement device that consists of a pair of wires of different metals or alloys welded together at a point to form a junction. The junction is exposed to the temperature to be measured, while the other end of the wires is connected to a reference junction at 0°C. The thermocouple produces a voltage difference between the two junctions that depends on the temperature difference.This voltage difference can be calibrated to give the temperature in degrees using a thermocouple table or a formula123

Wet chemical extinguishing agents, such as potassium acetate and potassium citrate, when sprayed on a grease fire, extinguish the fire by smothering and cooling. The wet chemical agent reacts with the hot grease and forms a layer of soap-like foam on the surface of the fat, which acts as an insulation between the hot grease and the atmosphere, preventing the escape of combustible vapors and oxygen supply.The wet chemical agent also absorbs heat from the grease and lowers its temperature below the ignition point12

References:

• What is the Difference Between a Wet and Dry Chemical Fire …
• Wet Chemical (Class K) Fire Extinguisher - Portable - WFX