Nevada Fixed Fire Extinguishing Systems Contractor Examination

Under NFPA 17 (2009), what is a dry chemical extinguishing agent?

• AA powder of very small particles, usually sodium bicarbonate-, potassium bicarbonate-, or…
• BA liquid potassium-acetate or potassium-citrate solution listed for commercial cooking
• CA liquefied compressed gas stored at 850 psi and 70°F
• DA protein hydrolysate mixed with water at 3 percent or 6 percent

Which dry chemical is the multipurpose (ABC) agent used on ordinary combustibles as well as flammable liquids and energized electrical equipment?

• ASodium bicarbonate
• BMonoammonium phosphate
• CPotassium bicarbonate (Purple-K)
• DUrea-based potassium bicarbonate only

What is a local-application dry chemical system under NFPA 17 (2009)?

• AA system that fills an entire enclosure to a uniform extinguishing concentration
• BA wheeled or hand-carried dry chemical extinguisher with no fixed piping
• CA supply of dry chemical permanently piped to nozzles that discharge directly onto the fi…
• DA water-sprinkler system with dry-pipe valves and dry chemical additive

What is a total-flooding dry chemical system intended to do?

• ACool a flammable-liquid surface with a floating aqueous film
• BReduce oxygen in the room to about 15 percent using stored nitrogen
• CDeliver water through closed-head sprinklers at a listed density
• DCreate a fire-extinguishing concentration of dry chemical in all parts of an enclosure

Which expellant must be used when recharging a dry chemical extinguishing cylinder unless the manufacturer recommends otherwise?

• ANitrogen or approved dry air
• BCarbon dioxide from a high-pressure cylinder
• COrdinary shop compressed air with no dryer
• DSteam or moist plant air

How often must the owner perform the NFPA 17 (2009) “quick check” inspection of a dry chemical system?

• AOnly after a discharge
• BAt least monthly
• COnce every 12 years at hydrostatic test
• DOnly when the AHJ requests it

What is a pre-engineered dry chemical system under NFPA 17 (2009) and NAC 477.180?

• AAny system whose pipe sizes are calculated from first principles on every job
• BA portable extinguisher mounted on a vehicle
• CA packaged, listed system installed only within the manufacturer’s pretested limitations
• DA foam-water deluge system listed to NFPA 16

Why must personnel-warning devices be provided on many dry chemical total-flooding and local-application systems?

• ADry chemical is always lethal at the listed design concentration
• BNFPA 17 requires a wintergreen odorizer on every dry chemical cylinder
• CDry chemical reduces oxygen to below 12 percent in every enclosure
• DA dry chemical discharge can obscure vision and impair breathing in the protected space

Which Class B/C dry chemical is commonly called Purple-K?

• APotassium bicarbonate
• BSodium bicarbonate
• CMonoammonium phosphate
• DPotassium acetate wet chemical

For an NFPA 17 (2009) total-flooding enclosure, unclosable openings up to what fraction of the total enclosure surface (sides, top, and bottom) need no extra dry chemical?

• A5 percent
• B1 percent
• C15 percent
• D25 percent

A total-flooding dry chemical enclosure has 8,000 ft² of total surface (sides, top, and bottom) and 240 ft² of unclosable openings. How much supplemental dry chemical does NFPA 17 (2009) require, and how is it applied?

• AAt least 240 lb applied by simultaneous local application over the openings
• BNo supplemental agent, because the openings are under 5 percent
• CAt least 120 lb through the regular distribution system
• DAt least 1,200 lb added to the flooding quantity

A paint-booth enclosure has 6,000 ft² of total surface and 480 ft² of unclosable openings. What NFPA 17 (2009) compensation applies?

• AAt least 240 lb added through the regular flooding nozzles only
• BNo extra agent; 8 percent is still within the 1 percent free allowance
• CConvert the system to a water-sprinkler deluge
• DAt least 480 lb of extra dry chemical applied simultaneously by local application over th…

Why does NFPA 17 (2009) prohibit mixing different types of dry chemical in the same cylinder or piping?

• AIncompatible powders can cake, react, or change flow and extinguishing performance
• BMixing always raises the hydrostatic test pressure above 600 psi
• CMixed powders become wet chemical and fall under NFPA 17A
• DDOT forbids any refill of a dry chemical cylinder

How often must a stored-pressure dry chemical system cylinder typically be hydrostatically tested when it remains in continuous service?

• AEvery month with the owner inspection
• BAt 12-year intervals, and whenever required by DOT or the listing
• CEvery 5 years for all dry chemical hardware without exception
• DNever, because dry chemical cylinders are exempt from pressure testing

After a dry chemical system discharges, what must be done before the hazard is left protected again?

• AOnly wipe residue off the nozzles; the remaining powder in the tank is enough
• BConvert the system to a closed-head water sprinkler
• CRecharge or replace the agent supply, restore detection and actuation, and return the sys…
• DWait 12 years for the next hydrostatic test before refilling

Which industrial hazards does NFPA 17 (2009) identify as typical local-application dry chemical candidates?

• AThe entire liquid surface of a 200-ft crude-oil cone-roof tank
• BA normally occupied data hall that must stay breathable after discharge
• CA light-hazard office protected only by NFPA 13 sprinklers
• DDip tanks, quenching-oil tanks, spray booths, oil-filled transformers, and similar open h…

Why do dry chemical discharge nozzles use blow-off caps or similar covers?

• ATo keep insects, grease, and debris out of the orifice until the system operates
• BTo increase the listed flow rate by 30 percent
• CTo convert the nozzle into a foam chamber
• DTo satisfy the NFPA 13 sprinkler-guard rule

A pre-engineered dry chemical installer wants to add two extra 90-degree elbows and 10 ft of pipe beyond the manufacturer’s listed limits. What is required?

• AAdd 25 percent more agent and proceed
• BDo not install it that way; the listing limits on pipe, fittings, and nozzles are mandato…
• CUse Schedule 80 pipe and ignore the listing
• DTreat the extra fittings as equivalent to a foam concentrate line

How often must a qualified person perform maintenance on a dry chemical extinguishing system under NFPA 17 (2009)?

• AOnly at the 12-year hydrostatic date
• BDaily, by the building owner
• CAt least semiannually, and after any actuation or impairment
• DOnce, at acceptance, with no further service

Sodium bicarbonate-based dry chemical is suitable for which fire classes in a fixed system?

• AClass A ordinary combustibles as a melting coating agent
• BClass D combustible metals such as magnesium and sodium
• CPolar-solvent alcohol fires that require AR-AFFF
• DClass B flammable liquids and gases and Class C energized electrical equipment

In the presence of moisture, potassium bicarbonate, sodium bicarbonate, and urea-based potassium bicarbonate dry chemicals can corrode which metals?

• AAluminum, aluminum brass, aluminum bronze, and titanium
• BOnly 304 and 316 stainless steel
• COnly gold and platinum electrical contacts
• DCast-iron dry-pipe valves on a water sprinkler riser

A closed-recovery dry chemical fill station is required in a Nevada shop that services fixed dry chemical systems. What is its purpose?

• ATo generate finished foam at 20:1 expansion
• BTo empty and refill cylinders without releasing powder into the workroom air
• CTo hydrostatically test CO2 cylinders to 3,000 psi
• DTo proportion 3 percent AFFF into a water stream

Why is the extinguishing action of a dry chemical total-flooding system described as transient?

• AThe powder continues to evolve CO2 for at least 20 minutes
• BThe system holds a 10-minute clean-agent concentration by enclosure integrity
• CThe suspended powder settles, so a lingering inert atmosphere is not maintained
• DDry chemical forms a permanent floating foam blanket on the fuel

When may a pre-engineered dry chemical system use opening-compensation quantities different from the 0.5 lb/ft² and 1 lb/ft² NFPA 17 (2009) rules?

• AWhenever the installer prefers a round number of cylinders
• BWhenever the enclosure exceeds 15 percent open area
• CNever; pre-engineered systems cannot protect any opening
• DOnly when the pre-engineered system is specifically listed for those different amounts

A 12-ft by 10-ft by 8-ft enclosed paint kitchen is to be total-flooded with a listed pre-engineered dry chemical unit whose maximum protected volume is 1,200 ft³. Which statement is correct?

• AThe volume is 960 ft³ and is within 1,200 ft³, but the listing still governs openings, no…
• BAny unit whose volume number is larger than 960 ft³ may be piped in any layout
• C960 ft³ always requires an engineered carbon dioxide system
• DC-41B pre-engineered systems have no listing volume limits

An enclosure measures 20 ft × 16 ft × 10 ft high. Unclosable openings total 48 ft² in the walls. What is the opening percentage, and what NFPA 17 (2009) compensation applies?

• AAbout 3.5 percent; add at least 48 lb as local application over the openings
• BAbout 3.5 percent; add at least 24 lb through the regular distribution system
• C1.5 percent; no compensation is required
• D8.0 percent; add 48 lb as local application

A listed pre-engineered dry chemical flow chart allows 3 nozzles, 30 ft of 1/2-in. pipe, and six 90-degree elbows from the tank. The layout needs 4 nozzles and eight elbows. What is the correct C-41B action?

• AInstall it and add 10 lb of agent for each extra elbow
• BUpsize the tank only and keep the extra fittings
• CStop and obtain a listed arrangement or an engineered design; the extra nozzle and elbows…
• DIgnore the chart because Nevada C-41B exams never test listing limits

A 4,000 ft² enclosure surface has 80 ft² of unclosable openings (2 percent) and a listed flooding quantity of 280 lb. What is the minimum total dry chemical that must be provided under the NFPA 17 (2009) 1–5 percent rule?

• A280 lb
• B360 lb
• C80 lb
• D320 lb

Why can a dry chemical total-flooding system that is sized only for a Class B vapor fire fail on a deep-seated ordinary-combustible fire in the same room?

• AMultipurpose dry chemical may still need additional local application on exposed Class A…
• BSodium bicarbonate always extinguishes Class A fuels better than MAP
• CNFPA 17 requires a 10-minute clean-agent hold that dry chemical automatically provides
• DClass A fires must be protected only with water sprinklers under C-41B

A listed dry chemical system uses fusible-link detection over a dip tank. The links are rated 360°F and are coated with process residue. What is the correct service action?

• AScrape the residue and reuse the same links indefinitely
• BReplace the links with new listed links of the same temperature rating and clean or repla…
• CSubstitute 165°F sprinkler bulbs because they are cheaper
• DRemove detection and leave the system manual-only to avoid nuisance trips

A 15 ft × 12 ft × 10 ft booth has 200 ft² of unclosable openings. What is the opening percentage, and what is the correct NFPA 17 (2009) path?

• AAbout 11 percent; apply 1 lb/ft² (200 lb) by local application over the openings and keep…
• BAbout 5 percent; apply 0.5 lb/ft² through the regular system
• CAbout 22 percent; the opening area exceeds 15 percent, so ordinary total-flood compensati…
• DAbout 1 percent; no compensation

What is the NFPA 12 (2015) minimum design concentration for a typical carbon dioxide total-flooding surface fire?

• A10 percent by volume
• B4 percent by volume
• C75 percent by volume for every Class B fuel
• D34 percent by volume

Within what time must the calculated carbon dioxide quantity for a surface-fire total-flooding system be discharged?

• A1 minute
• B10 seconds
• C7 minutes
• D20 minutes

At 70°F, a high-pressure carbon dioxide storage cylinder is at approximately what pressure?

• A300 psi
• B850 psi
• C150 psi
• D2,200 psi

How is a low-pressure carbon dioxide supply stored?

• AAs individual DOT cylinders at 850 psi and 70°F
• BAs a superpressurized 600 psi FK-5-1-12 cylinder
• CAs refrigerated bulk liquid at about 300 psi and 0°F
• DAs a dry chemical stored-pressure tank at 195 psi

What odorizer is commonly added to carbon dioxide so personnel can detect a leak or residual gas after discharge?

• AMercaptan as used in natural gas
• BChlorine
• CAmmonia
• DWintergreen (methyl salicylate)

At 70°F and 14.7 psia, one pound of carbon dioxide produces approximately how much vapor?

• A8.76 ft³
• B2.21 ft³
• C22.4 ft³
• D0.056 ft³

A carbon dioxide total-flooding system in a normally occupied or occupiable space that can expose people to more than 4 percent CO2 for more than 1 minute must include which warning device?

• AOnly a silent strobe, because CO2 is not hazardous below 34 percent
• BA pneumatic (pressure-operated) siren plus the required warning and caution signs
• CA wintergreen odorizer with no audible alarm
• DNo warning, because NFPA 12 treats 34 percent as a breathable atmosphere

What is the difference between a carbon dioxide total-flooding system and a local-application system?

• ATotal flooding is only for kitchens; local application is only for computer rooms
• BLocal application always uses water sprinklers as the discharge device
• CTotal flooding fills a capable enclosure to a design concentration; local application dis…
• DThere is no difference; NFPA 12 uses the terms interchangeably

For deep-seated carbon dioxide fires, the design concentration shall be reached within 7 minutes, but the flow rate shall not be less than that needed to produce what concentration in 2 minutes?

• A10 percent
• B4 percent
• C75 percent
• D30 percent

What minimum holding time does NFPA 12 require after a deep-seated carbon dioxide concentration is reached?

• A20 minutes
• B1 minute
• C10 seconds
• D55 minutes

Using the NFPA 12 surface-fire flooding-factor table, how much carbon dioxide is required for a 2,400 ft³ enclosure of ordinary 34 percent fuel with no special adjustments?

• A100 lb
• B134 lb
• C240 lb
• D77 lb

A 900 ft³ surface-fire enclosure of a 34 percent fuel is being sized from the NFPA 12 flooding-factor table. What quantity of CO2 is required before special adjustments?

• A35 lb
• B90 lb
• C57 lb
• D14 lb

Which NFPA 12 design concentration applies to dry electrical hazards (deep-seated) in a space of not more than 2,000 ft³?

• A34 percent, using 0.056 lb/ft³
• B75 percent, using 0.166 lb/ft³
• C9 percent, the HFC-227ea NOAEL
• D50 percent, using 0.100 lb/ft³ (10 ft³/lb)

Record or bulk paper storage, ducts, and covered trenches are carbon dioxide deep-seated hazards designed to which concentration?

• A65 percent (0.125 lb/ft³, 8 ft³/lb)
• B34 percent (0.056 lb/ft³)
• C50 percent (0.100 lb/ft³)
• D7 percent (HFC-227ea Class C)

Fur storage vaults and dust collectors are designed for which carbon dioxide concentration?

• A34 percent
• B75 percent (0.166 lb/ft³, 6 ft³/lb)
• C50 percent
• D10 percent

What is the minimum discharge time for a carbon dioxide local-application system on a liquid-surface fire?

• A10 seconds
• B1 minute for every local-application nozzle
• C30 seconds
• D7 minutes