,2026 NYC CUSTODIAN ENGINEER EXAM
COMPLETE PRACTICE TEST BANK — QUESTIONS 1-250
WITH CORRECT ANSWERS AND DETAILED RATIONALES
Question 1
What is the maximum allowable pressure for a low-pressure steam boiler
according to NYC Mechanical Code?
A) 5 psi
B) 10 psi
C) 15 psi
D) 30 psi
Answer: C) 15 psi
Rationale: Low-pressure steam boilers are limited to a maximum operating
pressure of 15 psig. Any boiler operating above this pressure is classified as a
high-pressure boiler and requires a different class of licensure and stricter
operating protocols. This is a critical safety limit that all custodians must
know and monitor daily.
Question 2
Which safety device automatically releases pressure from a boiler when it
exceeds the maximum safe operating pressure?
A) Low-water cutoff
B) Pressure relief valve
C) Thermostat
D) Feedwater regulator
,Answer: B) Pressure relief valve
Rationale: Safety relief valves are critical safety devices designed to
automatically open and release excess pressure when the boiler exceeds its
maximum operating pressure, preventing catastrophic boiler explosions.
These valves must be tested monthly by manually lifting the try lever to
ensure they operate freely and are not stuck.
Question 3
A Custodian Engineer detects a faint odor of natural gas in the boiler room.
What is the FIRST and most critical action to take?
A) Open windows to ventilate the area
B) Locate the main gas shut-off valve and close it
C) Evacuate the area and call 911 from a remote location
D) Use a gas detector to find the source of the leak
Answer: C) Evacuate the area and call 911 from a remote location
Rationale: Any action taken inside the boiler room, including using a phone,
operating electrical switches, or even turning on lights, could create a spark
and ignite the gas. Evacuation and calling 911 from a safe remote location is
the mandated first step per FDNY safety protocols. After evacuating, the
engineer should then close the main gas shut-off valve if it is safe to do so
from outside the building.
Question 4
What is the primary function of a low-water cutoff (LWCO) on a steam
boiler?
A) To regulate the water temperature
B) To shut off the burner if water level drops below a safe level
, C) To control the steam pressure
D) To circulate water through the system
Answer: B) To shut off the burner if water level drops below a safe level
Rationale: Low-water cutoffs are essential safety devices that automatically
shut down the burner when the water level drops below the safe operating
level. Without this protection, boiler tubes can overheat, weaken, and cause a
catastrophic boiler explosion. LWCO devices must be tested regularly by
simulating a low-water condition.
Question 5
What causes water hammer in steam piping systems?
A) High steam pressure
B) Low water pressure in the boiler
C) Condensate accumulation in steam lines propelled by flowing steam
D) Excessive water treatment chemicals
Answer: C) Condensate accumulation in steam lines propelled by
flowing steam
Rationale: Water hammer occurs when condensate (water) accumulates in
steam pipes and is propelled at high velocity by flowing steam. The impact of
the water slug against pipe fittings, valves, and elbows creates a loud
banging or hammering noise that can damage pipes and fittings. The
engineer must properly drain condensate from steam lines and ensure proper
pitch of piping to prevent water hammer.
Question 6
A boiler's pilot light fails to ignite. Which component should the engineer
check FIRST?
COMPLETE PRACTICE TEST BANK — QUESTIONS 1-250
WITH CORRECT ANSWERS AND DETAILED RATIONALES
Question 1
What is the maximum allowable pressure for a low-pressure steam boiler
according to NYC Mechanical Code?
A) 5 psi
B) 10 psi
C) 15 psi
D) 30 psi
Answer: C) 15 psi
Rationale: Low-pressure steam boilers are limited to a maximum operating
pressure of 15 psig. Any boiler operating above this pressure is classified as a
high-pressure boiler and requires a different class of licensure and stricter
operating protocols. This is a critical safety limit that all custodians must
know and monitor daily.
Question 2
Which safety device automatically releases pressure from a boiler when it
exceeds the maximum safe operating pressure?
A) Low-water cutoff
B) Pressure relief valve
C) Thermostat
D) Feedwater regulator
,Answer: B) Pressure relief valve
Rationale: Safety relief valves are critical safety devices designed to
automatically open and release excess pressure when the boiler exceeds its
maximum operating pressure, preventing catastrophic boiler explosions.
These valves must be tested monthly by manually lifting the try lever to
ensure they operate freely and are not stuck.
Question 3
A Custodian Engineer detects a faint odor of natural gas in the boiler room.
What is the FIRST and most critical action to take?
A) Open windows to ventilate the area
B) Locate the main gas shut-off valve and close it
C) Evacuate the area and call 911 from a remote location
D) Use a gas detector to find the source of the leak
Answer: C) Evacuate the area and call 911 from a remote location
Rationale: Any action taken inside the boiler room, including using a phone,
operating electrical switches, or even turning on lights, could create a spark
and ignite the gas. Evacuation and calling 911 from a safe remote location is
the mandated first step per FDNY safety protocols. After evacuating, the
engineer should then close the main gas shut-off valve if it is safe to do so
from outside the building.
Question 4
What is the primary function of a low-water cutoff (LWCO) on a steam
boiler?
A) To regulate the water temperature
B) To shut off the burner if water level drops below a safe level
, C) To control the steam pressure
D) To circulate water through the system
Answer: B) To shut off the burner if water level drops below a safe level
Rationale: Low-water cutoffs are essential safety devices that automatically
shut down the burner when the water level drops below the safe operating
level. Without this protection, boiler tubes can overheat, weaken, and cause a
catastrophic boiler explosion. LWCO devices must be tested regularly by
simulating a low-water condition.
Question 5
What causes water hammer in steam piping systems?
A) High steam pressure
B) Low water pressure in the boiler
C) Condensate accumulation in steam lines propelled by flowing steam
D) Excessive water treatment chemicals
Answer: C) Condensate accumulation in steam lines propelled by
flowing steam
Rationale: Water hammer occurs when condensate (water) accumulates in
steam pipes and is propelled at high velocity by flowing steam. The impact of
the water slug against pipe fittings, valves, and elbows creates a loud
banging or hammering noise that can damage pipes and fittings. The
engineer must properly drain condensate from steam lines and ensure proper
pitch of piping to prevent water hammer.
Question 6
A boiler's pilot light fails to ignite. Which component should the engineer
check FIRST?
