NYC Custodian Engineer Exam Questions
& Correct Answers Plus Rationales 2026
Q&A | Instant Download Pdf
(100%CORRECT )
1. A Custodian Engineer notices a faint odor of natural gas in a school boiler room.
What is the FIRST course of action?
a) Locate the main gas shut-off valve and close it.
b) Open all windows and doors to ventilate the area.
c) Evacuate the area and call 911 (or the gas utility) from a remote location.
d) Attempt to locate the leak using a soapy water solution.
Correct Answer: c) Evacuate the area and call 911 (or the gas utility) from a remote
location.
Rationale: Safety is paramount. Any action that could create a spark (using a phone in
the area, or even operating electrical switches like lights or fans) poses an ignition risk.
Evacuation and calling emergency services from a safe, remote location is the mandated
first step per FDNY and utility safety protocols.
2. When performing a routine inspection of a fire sprinkler system, the Custodian
Engineer observes that the water pressure gauge on the wet pipe system reads 20
psi below the normal range. What is the most likely cause?
a) A closed main control valve.
b) A faulty fire alarm control panel.
c) A tripped circuit breaker on the fire pump.
d) A small leak in the system or a compromised city water supply.
,Correct Answer: d) A small leak in the system or a compromised city water supply.
Rationale: A gradual drop in pressure indicates a loss of water, often due to a slow leak,
a defective check valve, or a fluctuation in the municipal water supply. If the main
control valve were closed, the pressure would typically drop to zero or static city
pressure with no flow. A fire pump is for boosting pressure; if it were tripped, the system
would rely solely on city pressure, which might be low.
3. According to NYC Fire Code, how often must fire drills be conducted in a K-12
educational facility?
a) Monthly
b) Bi-monthly (every two months)
c) Quarterly
d) Semi-annually
Correct Answer: a) Monthly
Rationale: The New York City Fire Code mandates that fire drills be conducted monthly
in educational facilities (K-12) while school is in session. This high frequency ensures that
students and staff are well-practiced in evacuation procedures.
4. A Custodian Engineer is troubleshooting a three-phase induction motor that
hums but fails to start. Which of the following is the most probable cause?
a) An open circuit in the run winding.
b) A seized bearing.
c) A single-phasing condition (loss of one phase).
d) A low voltage supply to all three phases.
Correct Answer: c) A single-phasing condition (loss of one phase).
Rationale: A three-phase motor that hums and won't start is a classic symptom of
single-phasing, where one of the three power lines is disconnected. The motor lacks the
rotating magnetic field needed to generate starting torque. A seized bearing (b) would
likely cause the motor to draw high current and trip the overloads, possibly humming
,briefly. Low voltage (d) might cause slow starting but not a complete failure to rotate
with a hum.
5. What is the primary function of a backflow preventer in a building's plumbing
system?
a) To regulate the water pressure entering the building.
b) To prevent potable water from being contaminated by non-potable water.
c) To filter sediment and debris from the main water supply.
d) To allow for the drainage of the system for winterization.
Correct Answer: b) To prevent potable water from being contaminated by non-
potable water.
Rationale: Backflow preventers are critical safety devices required by NYC Department
of Environmental Protection (DEP) regulations. They protect the public water supply by
ensuring that water can only flow in one direction, preventing reverse flow (backflow)
that could draw contaminants from boilers, irrigation systems, or other sources into the
potable water supply.
6. Which type of fire extinguisher is rated for use on electrical fires (Class C)?
a) Class A
b) Class B
c) Class K
d) Class ABC (dry chemical)
Correct Answer: d) Class ABC (dry chemical)
Rationale: Class C extinguishers are specifically for energized electrical equipment.
However, the most common multi-purpose extinguisher in NYC public buildings is the
ABC dry chemical type, which is effective on Class A (ordinary combustibles), Class B
(flammable liquids), and Class C (electrical) fires.
7. A low-pressure boiler has a pressure gauge that reads 8 psi. The safety valve is
stamped with a set pressure of 15 psi. Under normal operating conditions, what
should the operating pressure control be set to?
, a) 8 psi
b) 10 psi
c) 12 psi
d) 15 psi
Correct Answer: c) 12 psi
Rationale: Operating pressure controls should be set below the safety valve set point to
prevent the safety valve from lifting unnecessarily. A common practice is to set the
operating control 3-5 psi below the safety valve's set pressure. 12 psi provides a safe
buffer below the 15 psi safety valve limit, preventing nuisance releases and ensuring the
safety valve remains a final failsafe.
8. When performing preventive maintenance on a rooftop HVAC unit, what is the
primary reason for cleaning the condenser coils?
a) To prevent the growth of mold and bacteria.
b) To reduce the noise level of the condenser fan.
c) To improve heat transfer and system efficiency.
d) To prevent corrosion of the copper tubing.
Correct Answer: c) To improve heat transfer and system efficiency.
Rationale: Condenser coils reject heat to the outdoors. Dirt, dust, and debris act as
insulators, reducing the coil's ability to transfer heat. This causes higher head pressures,
increased energy consumption, and can lead to compressor failure. Cleaning is essential
for efficiency and longevity.
9. A Custodian Engineer receives a report of a "sulfur" or "rotten egg" smell from
a classroom sink. What is the most likely source?
a) A natural gas leak from a nearby appliance.
b) A dry P-trap allowing sewer gas to enter the room.
c) A leaking refrigerant line from an AC unit.
d) A dead animal in the wall cavity.
& Correct Answers Plus Rationales 2026
Q&A | Instant Download Pdf
(100%CORRECT )
1. A Custodian Engineer notices a faint odor of natural gas in a school boiler room.
What is the FIRST course of action?
a) Locate the main gas shut-off valve and close it.
b) Open all windows and doors to ventilate the area.
c) Evacuate the area and call 911 (or the gas utility) from a remote location.
d) Attempt to locate the leak using a soapy water solution.
Correct Answer: c) Evacuate the area and call 911 (or the gas utility) from a remote
location.
Rationale: Safety is paramount. Any action that could create a spark (using a phone in
the area, or even operating electrical switches like lights or fans) poses an ignition risk.
Evacuation and calling emergency services from a safe, remote location is the mandated
first step per FDNY and utility safety protocols.
2. When performing a routine inspection of a fire sprinkler system, the Custodian
Engineer observes that the water pressure gauge on the wet pipe system reads 20
psi below the normal range. What is the most likely cause?
a) A closed main control valve.
b) A faulty fire alarm control panel.
c) A tripped circuit breaker on the fire pump.
d) A small leak in the system or a compromised city water supply.
,Correct Answer: d) A small leak in the system or a compromised city water supply.
Rationale: A gradual drop in pressure indicates a loss of water, often due to a slow leak,
a defective check valve, or a fluctuation in the municipal water supply. If the main
control valve were closed, the pressure would typically drop to zero or static city
pressure with no flow. A fire pump is for boosting pressure; if it were tripped, the system
would rely solely on city pressure, which might be low.
3. According to NYC Fire Code, how often must fire drills be conducted in a K-12
educational facility?
a) Monthly
b) Bi-monthly (every two months)
c) Quarterly
d) Semi-annually
Correct Answer: a) Monthly
Rationale: The New York City Fire Code mandates that fire drills be conducted monthly
in educational facilities (K-12) while school is in session. This high frequency ensures that
students and staff are well-practiced in evacuation procedures.
4. A Custodian Engineer is troubleshooting a three-phase induction motor that
hums but fails to start. Which of the following is the most probable cause?
a) An open circuit in the run winding.
b) A seized bearing.
c) A single-phasing condition (loss of one phase).
d) A low voltage supply to all three phases.
Correct Answer: c) A single-phasing condition (loss of one phase).
Rationale: A three-phase motor that hums and won't start is a classic symptom of
single-phasing, where one of the three power lines is disconnected. The motor lacks the
rotating magnetic field needed to generate starting torque. A seized bearing (b) would
likely cause the motor to draw high current and trip the overloads, possibly humming
,briefly. Low voltage (d) might cause slow starting but not a complete failure to rotate
with a hum.
5. What is the primary function of a backflow preventer in a building's plumbing
system?
a) To regulate the water pressure entering the building.
b) To prevent potable water from being contaminated by non-potable water.
c) To filter sediment and debris from the main water supply.
d) To allow for the drainage of the system for winterization.
Correct Answer: b) To prevent potable water from being contaminated by non-
potable water.
Rationale: Backflow preventers are critical safety devices required by NYC Department
of Environmental Protection (DEP) regulations. They protect the public water supply by
ensuring that water can only flow in one direction, preventing reverse flow (backflow)
that could draw contaminants from boilers, irrigation systems, or other sources into the
potable water supply.
6. Which type of fire extinguisher is rated for use on electrical fires (Class C)?
a) Class A
b) Class B
c) Class K
d) Class ABC (dry chemical)
Correct Answer: d) Class ABC (dry chemical)
Rationale: Class C extinguishers are specifically for energized electrical equipment.
However, the most common multi-purpose extinguisher in NYC public buildings is the
ABC dry chemical type, which is effective on Class A (ordinary combustibles), Class B
(flammable liquids), and Class C (electrical) fires.
7. A low-pressure boiler has a pressure gauge that reads 8 psi. The safety valve is
stamped with a set pressure of 15 psi. Under normal operating conditions, what
should the operating pressure control be set to?
, a) 8 psi
b) 10 psi
c) 12 psi
d) 15 psi
Correct Answer: c) 12 psi
Rationale: Operating pressure controls should be set below the safety valve set point to
prevent the safety valve from lifting unnecessarily. A common practice is to set the
operating control 3-5 psi below the safety valve's set pressure. 12 psi provides a safe
buffer below the 15 psi safety valve limit, preventing nuisance releases and ensuring the
safety valve remains a final failsafe.
8. When performing preventive maintenance on a rooftop HVAC unit, what is the
primary reason for cleaning the condenser coils?
a) To prevent the growth of mold and bacteria.
b) To reduce the noise level of the condenser fan.
c) To improve heat transfer and system efficiency.
d) To prevent corrosion of the copper tubing.
Correct Answer: c) To improve heat transfer and system efficiency.
Rationale: Condenser coils reject heat to the outdoors. Dirt, dust, and debris act as
insulators, reducing the coil's ability to transfer heat. This causes higher head pressures,
increased energy consumption, and can lead to compressor failure. Cleaning is essential
for efficiency and longevity.
9. A Custodian Engineer receives a report of a "sulfur" or "rotten egg" smell from
a classroom sink. What is the most likely source?
a) A natural gas leak from a nearby appliance.
b) A dry P-trap allowing sewer gas to enter the room.
c) A leaking refrigerant line from an AC unit.
d) A dead animal in the wall cavity.
