This guide covers Maryland’s stationary engineer licensing end to end: the State Board of Stationary Engineers in the Department of Labor, the five grades and the horsepower of the largest single piece of plant machinery that assigns them, the PSI Qualification Information Bulletin’s examinations — sixty open-book questions at Grades 5 and 4, eighty closed-book at Grades 3, 2, and 1, seventy percent and one hundred twenty minutes throughout — the experience qualifications grade by grade, the sixty-five dollar PSI examination fee, and the content outlines PSI publishes, as set out in the Board’s pages and the PSI bulletin.
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The licence at a glance
| Item | Verified position |
|---|---|
| Licence | Maryland Stationary Engineer — Grades 1, 2, 3, 4, and 5 |
| Regulator | State Board of Stationary Engineers, Maryland Department of Labor (Division of Occupational and Professional Licensing) |
| Legal basis | Maryland Stationary Engineers Act, Business Occupations and Professions Article, Title 6.5, Annotated Code of Maryland; COMAR Title 09, Subtitle 17 |
| Grade 1 authority | Take charge of plant machinery of 500 or more horsepower (any building) |
| Grade 2 authority | 300 to 499 horsepower (any building) |
| Grade 3 authority | 100 to 299 horsepower (any building) |
| Grade 4 authority | 30 to 99 horsepower (any building regardless of use) |
| Grade 5 authority | 30 to 99 horsepower (in a building not open for public use) |
| Grade assignment rule | By the horsepower and operating pressure of the largest single piece of equipment in the plant, not the combined total (Board FAQ; Act section 6.5-302) |
| Examination vendor | PSI Services LLC — prior PSI approval required; examinations Monday through Friday by appointment at Maryland test centres |
| Grades 5 and 4 examination | 60 questions, 70% passing (42 items correct), 120 minutes, OPEN BOOK — listed references may be brought, under the bulletin’s marking and tabbing rules |
| Grades 3, 2, and 1 examination | 80 questions, 70% passing (56 items correct), 120 minutes, CLOSED BOOK |
| Examination fee | PSI examination registration fee $65 per sitting (a vendor fee per the PSI bulletin; valid for one examination, 90 days) |
| Direct entry | It is not necessary to start at a lower grade: an applicant may apply for any grade whose minimum requirements they meet (PSI bulletin) |
Maryland publishes more about its examinations than any other jurisdiction in this family — full content outlines with item counts, book rules down to the permitted brands of index tab, and qualification routes for every grade — because its examinations are built by a professional testing vendor to a board’s specification. This guide uses that published record in full: the PSI Qualification Information Bulletin’s outlines, forms, and fees, the Board’s grade authorities and its single-piece horsepower rule, and the two-step route in which the examination precedes the licence.
The regulator and the law behind the licence
The State Board of Stationary Engineers sits in the Division of Occupational and Professional Licensing of the Maryland Department of Labor. Its statutory home is the Maryland Stationary Engineers Act — Title 6.5 of the Business Occupations and Professions Article — with regulations at COMAR Title 09, Subtitle 17. The statewide board dates from 2005, when it replaced the Baltimore-centred Board of Examining Engineers whose licences had nonetheless been used across the state, usually for insurance purposes; the modern system’s statewide grades and PSI examinations are the product of that replacement.
The Board contracts its examination program to PSI Services LLC, and the division of labour is visible in the documents: the Board and the Act set the grades, their authorities, and the qualifications; PSI’s Qualification Information Bulletin operationalizes them — eligibility review, scheduling, the outlines, the book rules, score reporting. A Maryland candidate therefore reads two authorities at once, and this guide keeps them distinct: grades and qualifications from the Board, examination mechanics from the bulletin.
The five grades — in full
Each grade states its authority, the qualification routes the PSI bulletin publishes for its examination, and its examination form. The outlines are PSI’s published subject areas with their item counts.
Grade 5 — 30 to 99 horsepower, buildings not open for public use
The entry grade, and the only one whose qualification is educational rather than experiential: an applicant qualifies for the Grade 5 examination by possessing a high school diploma or graduate equivalence diploma. The licence it leads to is the system’s narrowest — charge of plant machinery from thirty to ninety-nine horsepower, in a building not open for public use: the private industrial and institutional plant whose boilers serve the building’s own operations rather than the visiting public. The examination is the sixty-question open-book sitting: general knowledge and problem solving carrying twenty of the sixty items, with basic electricity, boiler types and equipment, burners and fuel train, pumps and valves, inspections and maintenance, water treatment, emergency operations, and auxiliary equipment at five each.
The open-book rules are part of the examination: candidates may bring the listed reference books, indexed, highlighted, or underlined — but unmarked by writing, with no additional papers, and only the bulletin’s permitted self-adhesive tabs. Study guides are not allowed in the room.
Grade 4 — 30 to 99 horsepower, any building
Grade 4 removes Grade 5’s building restriction: the same horsepower band, in any building regardless of use — the grade for the operator of the school, the hospital annex, the public building. Qualification is by one of two routes: six months of documented experience as an active Grade 5 stationary engineer, or three credit hours or continuing education units of classes in boiler operations or safety together with verification of work experience. The examination is the same sixty-question, one-hundred-twenty-minute, open-book form as Grade 5, with the same published outline and passing standard of seventy percent — forty-two items correct.
Because Grades 5 and 4 share an examination form and outline, the honest study strategy is a single preparation aimed at the outline, with the grade distinction carried by the qualification route and the building restriction rather than by different questions.
Grade 3 — 100 to 299 horsepower
Grade 3 is the system’s hinge: the horsepower band rises to one hundred through two hundred ninety-nine, and the examination changes character — eighty questions, closed book, in the same one hundred twenty minutes, seventy percent requiring fifty-six correct. Qualification routes: two years of documented experience as an active Grade 4 or Grade 5 engineer; or one such year plus six credit hours or continuing education units in boiler operations or safety; or a valid marine engineer’s certificate or a United States Navy Chief Petty Officer’s certificate; or equivalent experience submitted to the Board. The outline deepens: sequential operations and central station and chillers enter, boiler types, burners, pumps, and sequential operations rise to ten items each, and general knowledge falls to ten.
The closed-book line at Grade 3 is the single most consequential fact in Maryland preparation: the candidate who prepared Grades 5 or 4 by learning where answers live in the reference books must, for Grade 3, learn the answers themselves.
Grade 2 — 300 to 499 horsepower
Grade 2 takes charge of plant machinery from three hundred to four hundred ninety-nine horsepower — the large institutional and industrial plant. Its principal qualification route is thirty-six months of documented experience as an active Grade 3 engineer under the direction and control of a licensed Grade 2 or Grade 1 engineer, with credit available: one year for six credit hours of boiler safety or operations classes, and one year for holding a current active licence as a master plumber, master HVACR contractor, or master restricted HVAC contractor. Alternative routes include a four-year mechanical engineering degree, licensing as a professional engineer with six months of documented experience at Grades 3 to 5, or a marine or Navy Chief Petty Officer certificate. The examination is eighty questions, closed book, seventy percent, with the outline’s weight shifted toward inspections and maintenance and water treatment at ten items each.
The direction-and-control clause matters to documentation: Grade 3 years count toward Grade 2 when they were served under the direction and control of a Grade 2 or Grade 1 engineer, so the applicant’s experience letters should say exactly that.
Grade 1 — 500 or more horsepower
The unlimited-floor grade: charge of plant machinery of five hundred or more horsepower in any building — the central plants of hospitals, universities, and industry. The principal route is five years of documented experience as an active Grade 2 engineer under the direction and control of a Grade 1 engineer, toward which the same class-credit and master-licence credits may be received. A four-year mechanical engineering degree is an alternative route, as is licensing as a professional engineer with one year of documented experience as a professional engineer and one year as a Grade 2 engineer under a Grade 1’s direction and control. The examination shares the eighty-question closed-book form and the Grade 2 outline family: burners, pumps, sequential operations, inspections, and water treatment at the heavy end.
Five documented years at Grade 2 makes Grade 1 the family’s longest qualification, and the bulletin is explicit that equivalent experience may be submitted to the Board for consideration and approval — the route for the candidate whose career does not match the printed ladder exactly.
Eligibility and experience, in full
Eligibility is grade-specific and documentary, and PSI reviews it before scheduling: the applicant uploads the required documentation, PSI processes it — the bulletin allows up to a week — and only the approved applicant may pay and schedule. The bulletin’s recurring currency is documented experience as an active licensee of the grade below, served, at the senior grades, under the direction and control of a licensee of the grade above, and every route ends with the same safety valve: equivalent experience may be submitted to the Board for consideration and approval.
Credit rules reward the classroom and the neighbouring trades: six credit hours or continuing education units in boiler operations or safety convert to a year of experience credit where the bulletin allows, and a current active licence as a master plumber, master HVACR contractor, or master restricted HVAC contractor likewise earns a year at the grades that name it. The degree routes — a four-year mechanical engineering degree, or professional-engineer licensing with specified operating experience — stand as full alternatives at Grades 2 and 1, and the marine and Navy certificates recur as alternatives at Grades 3 and 2.
The examination in detail
The bulletin’s five examinations share a skeleton — multiple choice, one hundred twenty minutes, seventy percent — and divide on the two variables that matter: count and books. Grades 5 and 4 present sixty questions and permit the listed references in the room; Grades 3, 2, and 1 present eighty questions and permit none. Passing scores are printed as item counts: forty-two of sixty, fifty-six of eighty.
The outlines repay close reading. Grades 5 and 4 rest on general knowledge and problem solving — twenty items, a third of the paper — over an eight-area base of five-item subjects. Grade 3 redistributes: general knowledge falls to ten, boiler types, burners, pumps, and sequential operations rise to ten, and central station and chillers appears. Grades 2 and 1 shift weight again toward inspections and maintenance and water treatment. The reference lists track the same divide: the open-book grades bring the boiler operator’s guide, the Maryland boiler safety act and regulations, the Stationary Engineers Act itself, and COMAR Title 09 Subtitle 17 into the room; the closed-book grades list those same works as preparation references that may not enter it.
Applying, scheduling, and fees
Apply to PSI, not to the Board: since September 2024 the application is online only — mailed, faxed, and emailed applications are returned — through PSI’s Maryland stationary engineer portal. Upload the grade’s eligibility documentation, allow the processing week, and on the approval email, pay the sixty-five dollar registration fee and schedule at a Maryland test centre. The fee buys one examination within ninety days; a missed appointment or late cancellation forfeits it under the bulletin’s procedures.
On examination day the bulletin requires the identification and security procedures of a professional test centre, and enforces the book rules at the door for the open-book grades: references may be indexed, highlighted, or underlined, but must carry no writing and no added papers, and tabs must be of the permanent self-adhesive kinds the bulletin names — removable flag tabs are expressly unacceptable. After a passing score, score reporting flows to the Department, and the licence application follows from the Department to the candidate.
Renewal and standing obligations
Licensing after examination is the Board’s, and the licence for the grade passed is the credential the holder thereafter maintains under the Act and COMAR Title 09, Subtitle 17. The PSI bulletin’s role ends at the examination; this guide states no renewal fee or continuing-education figure, because the bulletin relied on does not print them and the Board’s renewal terms are a separate publication — candidates should take renewal terms from the Board’s current licensing pages at the time they apply.
Licences from other jurisdictions
Maryland’s Act contemplates an examination-waiver possibility for an applicant holding an active licence in good standing in another state who otherwise meets Maryland’s requirements — but the Board’s published position is that Maryland currently holds no reciprocal agreement for a stationary engineer’s licence examination waiver with any other state. The practical route for the out-of-state engineer is therefore the Maryland route: PSI eligibility review on the strength of documented experience — where the equivalent-experience clause does real work — and the grade’s examination.
A study plan built to this examination
Prepare arithmetically, as the bulletin invites. Convert each outline into study weights: at Grades 5 and 4, a third of your time to general knowledge and problem solving, the rest spread evenly across the eight five-item areas; at Grade 3, to the four ten-item areas; at Grades 2 and 1, to the five areas the senior outlines weight heaviest. For the open-book grades, prepare the books as instruments — tab the act, the regulations, and the guide at the sections the outline names, within the bulletin’s tab rules — and practise timed retrieval: a fact found in ninety seconds is a mark; in four minutes, a loss.
For the closed-book grades, the same references become memory work: read them as the examiners wrote the questions from them, and drill the numbers Maryland runs on — the grade bands, the seventy percent line, the single-piece rule — until the administrative questions are reflexes. Sequence the campaign to the ninety-day fee window: apply when the preparation is nearly ripe, not before.
Examination day
At the test centre, expect PSI’s standard discipline: identity checked against the registration, security procedures, no unlisted materials. Open-book candidates should expect their references to be inspected against the bulletin’s rules — writing in a book, a loose paper, or a removable tab can cost the sitting. The one hundred twenty minutes is generous for sixty questions and exacting for eighty; the closed-book candidate should hold a ninety-second average and bank time for the sequential-operations sets.
Scores are reported through PSI to the Department; the passing candidate’s next document is the Department’s application for original licensing, and the Board’s licence for the grade passed completes the route the bulletin began.
Worked examples: the single-piece rule in practice
A university plant houses three boilers: two at two hundred horsepower and one at four hundred fifty. The plant’s combined nameplate is eight hundred fifty horsepower, and a candidate reasoning from totals would call it a Grade 1 plant. Maryland’s rule answers differently: the largest single piece is four hundred fifty horsepower, so the engineer in charge needs Grade 2. The Board prints this rule in its FAQ because it reverses the intuitive answer, and the PSI outlines test in a system built on it — candidates should run the single-piece analysis on every plant description they meet, in study and in the examination room.
Two smaller cases fix the floor. A private warehouse with a single eighty-horsepower boiler in a building not open for public use is Grade 5 territory — the one grade reachable on a diploma alone. Move the same boiler into a public school and the building limb changes the answer to Grade 4, at the same horsepower: identical machinery, different grade, decided entirely by the building’s public character. Maryland’s grades are as much about where the plant sits as what it is.
Finally, the candidate’s own file. A Grade 3 engineer with thirty months of service under a Grade 1’s direction and control, plus a current master HVACR licence, assembles the Grade 2 route from parts: thirty-six months required, one year of credit for the master licence where the bulletin allows it, and the balance in documented Grade 3 service. Building that file — months, credits, and the direction-and-control wording in the experience letters — is the unglamorous half of Maryland preparation, and it is the half PSI reviews before any question is asked.
What the PassProfessor program will cover
Practice in the examination’s own shape. Maryland’s PSI examinations are multiple-choice sittings of sixty questions (Grades 5 and 4, open book) or eighty questions (Grades 3, 2, and 1, closed book), each in one hundred twenty minutes at a seventy percent standard. The program in the works practises in those shapes: timed sets at the grade’s own count and pace, open-book technique drills for Grades 5 and 4 under the bulletin’s marking rules, and closed-book recall sets for Grades 3 to 1, with study weighted to PSI’s published outlines item by item.
Written from the primary sources. The program is written from the PSI Qualification Information Bulletin for the Maryland State Board of Stationary Engineers and the Board’s own pages — the outline counts, examination forms, fees, and qualification routes the bulletin prints, and the grade authorities the Act and the Board’s FAQ state. Where Maryland’s single-piece horsepower rule differs from other states’ plant-total rules, the program teaches the Maryland rule and names the difference.
The whole candidate, not only the test-taker. Around the item practice, the program carries the State Board of Stationary Engineers route as the authority publishes it — PSI approval and examination first, then the Board’s licence — with the grade set by the largest single piece of equipment in the plant — because a written examination is a means to a licence, and candidates plan better when the destination is mapped.
Preparation only. This is preparation for examinations administered by PSI for the Maryland State Board of Stationary Engineers. PassProfessor is not affiliated with PSI or the Board, no completion of this program is reported to either, and nothing in the program substitutes for the documented experience any grade requires or for any step in the licensing process.
Tell me when enrollment opens. The Maryland Stationary Engineer program is in the works and enrollment is not yet open. Leave an email address and PassProfessor will write to you when the program is ready — and only about this program. No date is promised, because the program will open when it meets the standard described above, not before.
Frequently asked questions
Why does Maryland use PSI rather than examining itself?
The Board contracts with PSI Services LLC to conduct its examination program. PSI reviews eligibility documentation, schedules and administers the examinations, and reports scores to the Department; the Board licenses.
What is the single-piece rule?
The grade of licence required — and the authority a grade carries — is set by the horsepower and operating pressure of the largest single piece of equipment in the plant, not the plant’s combined total. It is stated in the Act’s grade authorities and repeated in the Board’s FAQ.
Grades 5 and 4 have the same outline. Are they the same examination experience?
They share the published form — sixty questions, one hundred twenty minutes, open book, the same outline and passing standard. The grades differ in qualification route and in the licence’s building restriction: Grade 5 is limited to buildings not open for public use.
Exactly what may I write in my open-book references?
Nothing. The bulletin permits books that are indexed and contain highlighted or underlined text, but all materials must be unmarked — not written in — and may not contain additional papers, loose or attached. Study guides are not allowed at all.
Which tabs are acceptable?
The bulletin names permanent self-adhesive plastic index tabs (Avery Swift Tabs and Redi-Tag permanent adhesive) as acceptable, and Post-It index flags and flags as unacceptable — with the practical test that if the proctor can remove the tab without ripping the page, it comes out.
What counts as documented experience?
Experience the applicant can evidence to PSI’s review and the Board’s standard — service as an active licensee of the stated grade, under the direction and control the bulletin specifies at the senior grades, in the periods the routes state.
Can my master plumber licence really shorten the road to Grade 2?
The bulletin gives one year of credit toward the Grade 2 experience route for holding a current active licence as a master plumber, a master HVACR contractor, or a master restricted HVAC contractor — alongside a parallel one-year credit for six credit hours of boiler safety or operations classes.
Is the seventy percent scored differently at the open-book grades?
No. The standard is seventy percent at every grade, printed as forty-two of sixty items at Grades 5 and 4 and fifty-six of eighty at Grades 3, 2, and 1.
How long is my examination fee good for?
One examination, within ninety days of registration. The fee is not refundable and not transferable.
I hold a Grade 1 licence from another state. Must I examine?
Maryland currently has no reciprocal examination-waiver agreement with any other state, per the Board. Your documented experience may be presented — including under the equivalent-experience provision — but the grade’s PSI examination remains part of the route.
Where are the test centres?
The Board’s pages list PSI centres in Baltimore, College Park, Hagerstown, Lanham, and Salisbury, with examinations Monday through Friday by appointment; the bulletin describes six Maryland test centres. Confirm the current list when you schedule.
Does the bulletin cover licence renewal?
No — the bulletin ends at licensing’s threshold. Renewal terms come from the Board’s licensing publications, and this guide states no renewal fee the bulletin does not print.
What references are listed for the closed-book grades?
The same core works as the open-book grades — the boiler operator’s guide, the pump handbook, modern refrigeration and air conditioning, the electric circuits texts, the Maryland boiler safety act and regulations, the Stationary Engineers Act, and COMAR Title 09 Subtitle 17 — listed as preparation references that are not allowed in the examination room.
Does this program help with the PSI eligibility paperwork?
The program prepares candidates for the written examination and maps the route as published. The eligibility determination itself is PSI’s and the Board’s, on the documents the applicant submits.