NYC CUSTODIAN ENGINEER EXAM 350 QUESTIONS WITH
VERIFIED SOLUTIONS & DETAILED RATIONALES LATEST
UPDATE | ACTUAL EXAM MCQs STYLE| EXPERT VERIFIED FOR
GUARANTEED PASS 2026
SHORT POINT FORM (QUICK REVISION)
- Boilers → operation, pressure, safety valves, water level, blowdown
- HVAC → airflow, filters, maintenance, thermostats, chillers
- Electrical → circuits, breakers, safety, lighting, motors
- Fire Safety → alarms, extinguishers, evacuation, sprinklers
- Plumbing → leaks, drainage, fixtures, backflow prevention
- Codes → OSHA, NYC regulations, DOB, DEP
- Custodial → cleaning, supervision, floor care, supplies
- Records → logs, compliance, maintenance schedules
- Safety → PPE, hazard control, lockout/tagout
SECTION 1: BOILER OPERATION AND MAINTENANCE (Questions 1–50)
Q1. When operating a low-pressure steam boiler in a school building, what is the
most critical safety device that must be checked regularly to prevent overpressure
conditions?
A. Thermostat
B. Pressure relief valve
C. Circulating pump
D. Expansion tank
Correct Answer: B
Rationale: The pressure relief valve is the primary safety device that prevents
dangerous pressure buildup. If pressure exceeds the set point, the valve opens to
release steam. The thermostat controls temperature, the circulating pump moves
water, and the expansion tank accommodates water expansion. None prevent
overpressure like the relief valve.
Reference: NYC Building Code § 1008; ASME Boiler and Pressure Vessel Code
1
,Q2. During routine maintenance, a custodian engineer notices uneven heating in
classrooms. What is the most likely cause within a steam heating system?
A. Dirty burner
B. Air trapped in radiators
C. Low water pressure
D. Faulty thermostat
Correct Answer: B
Rationale: Air trapped in steam radiators prevents steam from entering, causing
uneven or no heat. Bleeding the radiators releases trapped air. A dirty burner
affects heat production, low water pressure affects the entire system, and a faulty
thermostat affects individual room control but not systemic uneven heating.
Reference: NYC DEP Steam System Guidelines
Q3. What is the proper water level in a boiler sight glass?
A. Completely full
B. Completely empty
C. Approximately half to two-thirds full
D. One-quarter full
Correct Answer: C
Rationale: The correct water level in a boiler sight glass is approximately half to
two-thirds full. This ensures adequate water for steam production while leaving
space for expansion. A full sight glass may indicate carryover or flooding; an
empty sight glass indicates low water, which is dangerous.
Reference: ASME Boiler Code; NYC Boiler Operating Instructions
Q4. How often should the low-water cutoff device on a steam boiler be tested?
A. Daily
B. Weekly
C. Monthly
D. Annually
Correct Answer: B
2
,Rationale: The low-water cutoff should be tested weekly to ensure it will shut
down the burner if water drops to unsafe levels. Daily testing is excessive;
monthly or annually is too infrequent and risks boiler damage.
Reference: NYC Building Code; ASME CSD-1
Q5. A custodian engineer notices the boiler pressure gauge reading is fluctuating
widely. What is the most likely cause?
A. Defective gauge or water level fluctuation
B. High fuel pressure
C. Clogged burner nozzle
D. Overfilled expansion tank
Correct Answer: A
Rationale: Wide fluctuations in pressure gauge readings typically indicate a
defective gauge (sticking or worn mechanism) or water level fluctuations causing
steam pressure changes. High fuel pressure affects flame, not pressure reading; a
clogged nozzle affects combustion; an overfilled expansion tank affects water
expansion but not pressure readings.
Reference: Boiler maintenance manuals
Q6. What is the maximum allowable working pressure for a low-pressure steam
boiler?
A. 15 PSI
B. 30 PSI
C. 50 PSI
D. 100 PSI
Correct Answer: A
Rationale: By definition, a low-pressure steam boiler operates at or below 15 PSI.
High-pressure boilers operate above 15 PSI. 30 PSI, 50 PSI, and 100 PSI exceed
low-pressure limits.
Reference: ASME Section IV; NYC Building Code
Q7. During a boiler blowdown procedure, the operator should:
A. Open the blowdown valve fully and close immediately
3
, B. Open the blowdown valve, allow water to discharge, and close slowly
C. Never perform a blowdown
D. Open only the surface blowdown valve
Correct Answer: B
Rationale: Proper blowdown involves opening the valve, allowing the discharge to
flush sediment from the bottom, and closing slowly to prevent water hammer.
Immediate closing does not clear sediment; never performing blowdown allows
sludge buildup.
Reference: Boiler operation manuals; ASME guidelines
Q8. A boiler's safety relief valve must be tested:
A. Annually by a qualified technician
B. Monthly by the custodian
C. Only when pressure is abnormal
D. Once per shift
Correct Answer: A
Rationale: Safety relief valves must be tested annually by a certified technician to
ensure proper operation. Monthly testing by custodians is not recommended due
to safety risks; testing only when abnormal is too late; daily testing is excessive
and can damage the valve.
Reference: ASME Section VI; NYC DOB
Q9. What is the purpose of a boiler's low-water cutoff?
A. To maintain water temperature
B. To shut off the burner if water drops below safe level
C. To regulate steam pressure
D. To circulate water through the boiler
Correct Answer: B
Rationale: The low-water cutoff is a safety device that shuts down the burner
when water level drops to prevent boiler damage or explosion. It does not
maintain temperature (thermostat does); does not regulate pressure (pressure
controls do); does not circulate water (pump does).
Reference: ASME CSD-1
4
VERIFIED SOLUTIONS & DETAILED RATIONALES LATEST
UPDATE | ACTUAL EXAM MCQs STYLE| EXPERT VERIFIED FOR
GUARANTEED PASS 2026
SHORT POINT FORM (QUICK REVISION)
- Boilers → operation, pressure, safety valves, water level, blowdown
- HVAC → airflow, filters, maintenance, thermostats, chillers
- Electrical → circuits, breakers, safety, lighting, motors
- Fire Safety → alarms, extinguishers, evacuation, sprinklers
- Plumbing → leaks, drainage, fixtures, backflow prevention
- Codes → OSHA, NYC regulations, DOB, DEP
- Custodial → cleaning, supervision, floor care, supplies
- Records → logs, compliance, maintenance schedules
- Safety → PPE, hazard control, lockout/tagout
SECTION 1: BOILER OPERATION AND MAINTENANCE (Questions 1–50)
Q1. When operating a low-pressure steam boiler in a school building, what is the
most critical safety device that must be checked regularly to prevent overpressure
conditions?
A. Thermostat
B. Pressure relief valve
C. Circulating pump
D. Expansion tank
Correct Answer: B
Rationale: The pressure relief valve is the primary safety device that prevents
dangerous pressure buildup. If pressure exceeds the set point, the valve opens to
release steam. The thermostat controls temperature, the circulating pump moves
water, and the expansion tank accommodates water expansion. None prevent
overpressure like the relief valve.
Reference: NYC Building Code § 1008; ASME Boiler and Pressure Vessel Code
1
,Q2. During routine maintenance, a custodian engineer notices uneven heating in
classrooms. What is the most likely cause within a steam heating system?
A. Dirty burner
B. Air trapped in radiators
C. Low water pressure
D. Faulty thermostat
Correct Answer: B
Rationale: Air trapped in steam radiators prevents steam from entering, causing
uneven or no heat. Bleeding the radiators releases trapped air. A dirty burner
affects heat production, low water pressure affects the entire system, and a faulty
thermostat affects individual room control but not systemic uneven heating.
Reference: NYC DEP Steam System Guidelines
Q3. What is the proper water level in a boiler sight glass?
A. Completely full
B. Completely empty
C. Approximately half to two-thirds full
D. One-quarter full
Correct Answer: C
Rationale: The correct water level in a boiler sight glass is approximately half to
two-thirds full. This ensures adequate water for steam production while leaving
space for expansion. A full sight glass may indicate carryover or flooding; an
empty sight glass indicates low water, which is dangerous.
Reference: ASME Boiler Code; NYC Boiler Operating Instructions
Q4. How often should the low-water cutoff device on a steam boiler be tested?
A. Daily
B. Weekly
C. Monthly
D. Annually
Correct Answer: B
2
,Rationale: The low-water cutoff should be tested weekly to ensure it will shut
down the burner if water drops to unsafe levels. Daily testing is excessive;
monthly or annually is too infrequent and risks boiler damage.
Reference: NYC Building Code; ASME CSD-1
Q5. A custodian engineer notices the boiler pressure gauge reading is fluctuating
widely. What is the most likely cause?
A. Defective gauge or water level fluctuation
B. High fuel pressure
C. Clogged burner nozzle
D. Overfilled expansion tank
Correct Answer: A
Rationale: Wide fluctuations in pressure gauge readings typically indicate a
defective gauge (sticking or worn mechanism) or water level fluctuations causing
steam pressure changes. High fuel pressure affects flame, not pressure reading; a
clogged nozzle affects combustion; an overfilled expansion tank affects water
expansion but not pressure readings.
Reference: Boiler maintenance manuals
Q6. What is the maximum allowable working pressure for a low-pressure steam
boiler?
A. 15 PSI
B. 30 PSI
C. 50 PSI
D. 100 PSI
Correct Answer: A
Rationale: By definition, a low-pressure steam boiler operates at or below 15 PSI.
High-pressure boilers operate above 15 PSI. 30 PSI, 50 PSI, and 100 PSI exceed
low-pressure limits.
Reference: ASME Section IV; NYC Building Code
Q7. During a boiler blowdown procedure, the operator should:
A. Open the blowdown valve fully and close immediately
3
, B. Open the blowdown valve, allow water to discharge, and close slowly
C. Never perform a blowdown
D. Open only the surface blowdown valve
Correct Answer: B
Rationale: Proper blowdown involves opening the valve, allowing the discharge to
flush sediment from the bottom, and closing slowly to prevent water hammer.
Immediate closing does not clear sediment; never performing blowdown allows
sludge buildup.
Reference: Boiler operation manuals; ASME guidelines
Q8. A boiler's safety relief valve must be tested:
A. Annually by a qualified technician
B. Monthly by the custodian
C. Only when pressure is abnormal
D. Once per shift
Correct Answer: A
Rationale: Safety relief valves must be tested annually by a certified technician to
ensure proper operation. Monthly testing by custodians is not recommended due
to safety risks; testing only when abnormal is too late; daily testing is excessive
and can damage the valve.
Reference: ASME Section VI; NYC DOB
Q9. What is the purpose of a boiler's low-water cutoff?
A. To maintain water temperature
B. To shut off the burner if water drops below safe level
C. To regulate steam pressure
D. To circulate water through the boiler
Correct Answer: B
Rationale: The low-water cutoff is a safety device that shuts down the burner
when water level drops to prevent boiler damage or explosion. It does not
maintain temperature (thermostat does); does not regulate pressure (pressure
controls do); does not circulate water (pump does).
Reference: ASME CSD-1
4
