D C 3 R D C L A S S B O I L E R O P E R AT O R · C E R T I F I C AT I O N
E X A M I N AT I O N
DC BOILER
EXAM PREP
2026/2027
120 certification-style questions with complete
solutions, aligned with ASME code practice and
District of Columbia licensing standards.
120 Questions · 7 Sections · Complete Solutions
Formulas and Constants · Design and Safety · Operations · Water
Treatment · Combustion · Auxiliaries · DC Regulations
F O R M U L A S A N D C O N S TA N T S E D I T I O N — 2 0 2 0 2 7
,DC BOILER EXAM PREP 2026/2027 - 3RD CLASS BOILER OPERATOR QUESTIONS WITH COMPLETE SOLUTIONS
Table of Contents
EXAMINATION OVERVIEW 2
SECTION 1 - BOILER FORMULAS AND CONSTANTS (Questions 1-25) 3
SECTION 2 - DESIGN, CONSTRUCTION, AND SAFETY (Questions 26-45) 12
SECTION 3 - BOILER OPERATIONS AND CONTROLS (Questions 46-65) 19
SECTION 4 - WATER TREATMENT AND CHEMISTRY (Questions 66-80) 26
SECTION 5 - COMBUSTION AND FUELS (Questions 81-95) 32
SECTION 6 - PUMPS, DRIVES, AND AUXILIARY EQUIPMENT (Questions 96-110) 37
SECTION 7 - DC REGULATIONS, LICENSING, AND CODE COMPLIANCE (Questions
111-120) 42
APPENDIX A - QUICK-REFERENCE ANSWER KEY 47
DC 3rd Class Boiler Operator Certification Practice 1
,DC BOILER EXAM PREP 2026/2027 - 3RD CLASS BOILER OPERATOR QUESTIONS WITH COMPLETE SOLUTIONS
EXAMINATION OVERVIEW
This preparation examination contains 120 multiple-choice questions with complete solutions, written to the
scope of the District of Columbia Third Class Boiler Operator certification. The questions follow the DC
licensing framework, ASME Boiler and Pressure Vessel Code practice, and ASME CSD-1
burner-management requirements, and they are organized into seven sections that mirror the topics covered
on the actual examination: formulas and constants, design and construction safety, operations and controls,
water treatment and chemistry, combustion and fuels, pumps and auxiliary equipment, and DC regulations
and licensing.
The question mix is deliberately weighted the way licensing examinations are weighted. Approximately 70
percent of the items are scenario-based, placing you in the operator's chair at a working plant and asking for
a judgment or a calculation; the remaining 30 percent are direct knowledge items covering formulas,
constants, and code facts. The cognitive levels are balanced at roughly 25 percent recall, 50 percent
application, and 25 percent analysis, so you will be tested on remembering the rule, using the rule, and
recognizing when the rule has been broken. Distractors throughout include the classic formula errors,
unit-conversion traps, operational misconceptions, and code misunderstandings that examiners rely on.
Work each question before reading its solution. Every solution restates the correct option, identifies the
answer letter, and explains why the answer is right and why the tempting distractors are wrong, citing the
relevant ASME section or DC exam standard where applicable. Candidates who can score a consistent 90
percent or better on this practice set, without reference material, are generally well prepared for the DC
Third Class examination. A quick-reference answer key appears in the appendix for review and self-scoring.
Section Focus Area Questions Primary Skills
Area, work, power, gas laws, BHP,
1 Boiler Formulas and Constants 1-25
MAWP
ASME I/IV, CSD-1, safety valves, level
2 Design, Construction, and Safety 26-45
protection
Start-up, shutdown, feedwater control,
3 Boiler Operations and Controls 46-65
layup
pH, TDS, softeners, oxygen scavenging,
4 Water Treatment and Chemistry 66-80
blowdown
Air requirements, fuel values, flue gas
5 Combustion and Fuels 81-95
analysis
Pump math, cavitation, traps, electrical
6 Pumps, Drives, and Auxiliaries 96-110
basics
License scope, logs, inspections, code
7 DC Regulations and Licensing 111-120
compliance
Table 1. Examination structure and question distribution.
DC 3rd Class Boiler Operator Certification Practice 2
, DC BOILER EXAM PREP 2026/2027 - 3RD CLASS BOILER OPERATOR QUESTIONS WITH COMPLETE SOLUTIONS
HOW TO USE THIS EXAMINATION
Simulate exam conditions. Set aside uninterrupted time, work through a full section at a sitting, and answer
every question before consulting any solution. Exam stamina and pacing are skills of their own, and licensing
exams rarely allow reference material.
Score by section, not just in total. A 90 percent overall score can still hide a 50 percent score in one
section. Your weakest section, not your average, is where the licensing examiner will find you, so drill the
weak topic until its numbers match the rest.
Read every distractor explanation. Each solution explains why the wrong answers are wrong, because
those wrong answers are built from the formula and unit errors that appear on the real exam. Understanding
the traps is as valuable as memorizing the constants.
Memorize the constants sheet. The DC 3rd class exam expects fluency with 0.7854, 34.5 lb/BHP, 33,475
Btu/BHP, 970.3, 144, 62.4, 8.33, 7.48, 2.31 ft per psi, 0.433 psi per foot, 33,000 ft-lb/min, 3,960, 1.732, and
17.1 ppm per gpg. Keep drilling until each constant is automatic.
SECTION 1 - BOILER FORMULAS AND CONSTANTS
(Questions 1-25)
Q1. A boiler room floor measures 45 ft long by 28 ft wide. Before new refractory tile is ordered for a
maintenance lay-down area, the engineer must calculate the floor area. What is the area in square feet?
A. 630 ft2
B. 1,575 ft2
C. 1,260 ft2
D. 146 ft2
C. 1,260 ft2 [CORRECT]
Correct Answer: C
Explanation: Area of a rectangle equals length times width: 45 ft × 28 ft = 1,260 ft2. The value 146 ft2 is
the perimeter result (2 × (45 + 28)), a common error when the two dimensions are added instead of
multiplied. DC 3rd class exam standards require fluency with basic area formulas before any steam-sizing
work.
Q2. Which formula gives the area of a circle when the diameter D is known, as used for circular patches,
tank ends, and manway openings?
A. A = π × D
B. A = 0.7854 × D2
C. A = 0.7854 × D
D. A = D2
B. A = 0.7854 × D2 [CORRECT]
DC 3rd Class Boiler Operator Certification Practice 3
E X A M I N AT I O N
DC BOILER
EXAM PREP
2026/2027
120 certification-style questions with complete
solutions, aligned with ASME code practice and
District of Columbia licensing standards.
120 Questions · 7 Sections · Complete Solutions
Formulas and Constants · Design and Safety · Operations · Water
Treatment · Combustion · Auxiliaries · DC Regulations
F O R M U L A S A N D C O N S TA N T S E D I T I O N — 2 0 2 0 2 7
,DC BOILER EXAM PREP 2026/2027 - 3RD CLASS BOILER OPERATOR QUESTIONS WITH COMPLETE SOLUTIONS
Table of Contents
EXAMINATION OVERVIEW 2
SECTION 1 - BOILER FORMULAS AND CONSTANTS (Questions 1-25) 3
SECTION 2 - DESIGN, CONSTRUCTION, AND SAFETY (Questions 26-45) 12
SECTION 3 - BOILER OPERATIONS AND CONTROLS (Questions 46-65) 19
SECTION 4 - WATER TREATMENT AND CHEMISTRY (Questions 66-80) 26
SECTION 5 - COMBUSTION AND FUELS (Questions 81-95) 32
SECTION 6 - PUMPS, DRIVES, AND AUXILIARY EQUIPMENT (Questions 96-110) 37
SECTION 7 - DC REGULATIONS, LICENSING, AND CODE COMPLIANCE (Questions
111-120) 42
APPENDIX A - QUICK-REFERENCE ANSWER KEY 47
DC 3rd Class Boiler Operator Certification Practice 1
,DC BOILER EXAM PREP 2026/2027 - 3RD CLASS BOILER OPERATOR QUESTIONS WITH COMPLETE SOLUTIONS
EXAMINATION OVERVIEW
This preparation examination contains 120 multiple-choice questions with complete solutions, written to the
scope of the District of Columbia Third Class Boiler Operator certification. The questions follow the DC
licensing framework, ASME Boiler and Pressure Vessel Code practice, and ASME CSD-1
burner-management requirements, and they are organized into seven sections that mirror the topics covered
on the actual examination: formulas and constants, design and construction safety, operations and controls,
water treatment and chemistry, combustion and fuels, pumps and auxiliary equipment, and DC regulations
and licensing.
The question mix is deliberately weighted the way licensing examinations are weighted. Approximately 70
percent of the items are scenario-based, placing you in the operator's chair at a working plant and asking for
a judgment or a calculation; the remaining 30 percent are direct knowledge items covering formulas,
constants, and code facts. The cognitive levels are balanced at roughly 25 percent recall, 50 percent
application, and 25 percent analysis, so you will be tested on remembering the rule, using the rule, and
recognizing when the rule has been broken. Distractors throughout include the classic formula errors,
unit-conversion traps, operational misconceptions, and code misunderstandings that examiners rely on.
Work each question before reading its solution. Every solution restates the correct option, identifies the
answer letter, and explains why the answer is right and why the tempting distractors are wrong, citing the
relevant ASME section or DC exam standard where applicable. Candidates who can score a consistent 90
percent or better on this practice set, without reference material, are generally well prepared for the DC
Third Class examination. A quick-reference answer key appears in the appendix for review and self-scoring.
Section Focus Area Questions Primary Skills
Area, work, power, gas laws, BHP,
1 Boiler Formulas and Constants 1-25
MAWP
ASME I/IV, CSD-1, safety valves, level
2 Design, Construction, and Safety 26-45
protection
Start-up, shutdown, feedwater control,
3 Boiler Operations and Controls 46-65
layup
pH, TDS, softeners, oxygen scavenging,
4 Water Treatment and Chemistry 66-80
blowdown
Air requirements, fuel values, flue gas
5 Combustion and Fuels 81-95
analysis
Pump math, cavitation, traps, electrical
6 Pumps, Drives, and Auxiliaries 96-110
basics
License scope, logs, inspections, code
7 DC Regulations and Licensing 111-120
compliance
Table 1. Examination structure and question distribution.
DC 3rd Class Boiler Operator Certification Practice 2
, DC BOILER EXAM PREP 2026/2027 - 3RD CLASS BOILER OPERATOR QUESTIONS WITH COMPLETE SOLUTIONS
HOW TO USE THIS EXAMINATION
Simulate exam conditions. Set aside uninterrupted time, work through a full section at a sitting, and answer
every question before consulting any solution. Exam stamina and pacing are skills of their own, and licensing
exams rarely allow reference material.
Score by section, not just in total. A 90 percent overall score can still hide a 50 percent score in one
section. Your weakest section, not your average, is where the licensing examiner will find you, so drill the
weak topic until its numbers match the rest.
Read every distractor explanation. Each solution explains why the wrong answers are wrong, because
those wrong answers are built from the formula and unit errors that appear on the real exam. Understanding
the traps is as valuable as memorizing the constants.
Memorize the constants sheet. The DC 3rd class exam expects fluency with 0.7854, 34.5 lb/BHP, 33,475
Btu/BHP, 970.3, 144, 62.4, 8.33, 7.48, 2.31 ft per psi, 0.433 psi per foot, 33,000 ft-lb/min, 3,960, 1.732, and
17.1 ppm per gpg. Keep drilling until each constant is automatic.
SECTION 1 - BOILER FORMULAS AND CONSTANTS
(Questions 1-25)
Q1. A boiler room floor measures 45 ft long by 28 ft wide. Before new refractory tile is ordered for a
maintenance lay-down area, the engineer must calculate the floor area. What is the area in square feet?
A. 630 ft2
B. 1,575 ft2
C. 1,260 ft2
D. 146 ft2
C. 1,260 ft2 [CORRECT]
Correct Answer: C
Explanation: Area of a rectangle equals length times width: 45 ft × 28 ft = 1,260 ft2. The value 146 ft2 is
the perimeter result (2 × (45 + 28)), a common error when the two dimensions are added instead of
multiplied. DC 3rd class exam standards require fluency with basic area formulas before any steam-sizing
work.
Q2. Which formula gives the area of a circle when the diameter D is known, as used for circular patches,
tank ends, and manway openings?
A. A = π × D
B. A = 0.7854 × D2
C. A = 0.7854 × D
D. A = D2
B. A = 0.7854 × D2 [CORRECT]
DC 3rd Class Boiler Operator Certification Practice 3
