# Maryland — US boiler and pressure vessel inspection requirements by state For Maryland, governing body is Department of Labor, Licensing and Regulation's Safety Inspections Unit; statute citation is Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9; power boiler inspection interval is annual internal inspections, where construction permits and annual external inspections performed while under pressure; low-pressure boiler inspection interval is biennial certificate inspections; accepted inspector types is commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request, recorded from its source on 2026-08-05. - **State:** Maryland _(verified: appears in the quote below)_ - **Governing body:** Department of Labor, Licensing and Regulation's Safety Inspections Unit - **Statute citation:** Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9 _(verified: appears in the quote below)_ - **Power boiler inspection interval:** annual internal inspections, where construction permits and annual external inspections performed while under pressure _(verified: appears in the quote below)_ - **Low-pressure boiler inspection interval:** biennial certificate inspections _(verified: appears in the quote below)_ - **Accepted inspector types:** commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request _(verified: appears in the quote below)_ - **Pressure vessel inspection interval:** Pressure vessels: a biennial certificate inspection. _(per nationalboard.org, not stated by the source above)_ - **Exemptions:** Boilers and pressure vessels under federal control or regulation. Pressure vessels used for the transportation and storage of compressed gases when constructed in compliance with specifications of the US Department of Transportation. Air tanks installed on the right-of-way of railroads and used directly in the operation of trains. Air tanks located on vehicles operating under the rules of other state authorities. Pressure vessels operating at a working pressure not exceeding 15 psig. Hot-water supply boilers directly fired with oil, gas, or electricity when none of the following limitations is exceeded: A heat input of 200,000 BTU per hour; A water temperature of 210°F; A nominal water-containing capacity of 120 gallons. Boilers or pressure vessels located on farms and used solely for agricultural purposes. Heating boilers which are located in private residences or in apartment houses of fewer than six family units. _(per nationalboard.org, not stated by the source above)_ ## What the source says > Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9. Authorized inspector types: Maryland accepts commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request. Inspection frequency: High-pressure boilers require annual internal inspections, where construction permits and annual external inspections are performed while under pressure. Low-pressure boilers require biennial certificate inspections. ## Sources disagree More than one authority states this, and they do not state the same thing. Both are reproduced with the source each came from. ### Governing body chardonlabs.com says governing body is **Department of Labor, Licensing and Regulation's Safety Inspections Unit**, as of 2026-08-05. > Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9. Authorized inspector types: Maryland accepts commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request. Inspection frequency: High-pressure boilers require annual internal inspections, where construction permits and annual external inspections are performed while under pressure. Low-pressure boilers require biennial certificate inspections. Source: https://www.chardonlabs.com/resources/commercial-boiler-inspection-regulations-by-state/ nationalboard.org says governing body is **Department of Labor, Licensing, and Regulation, Division of Labor and Industry, Safety Inspections Unit, Boilers and Pressure Vessels**, as of 2026-08-05. > Power boilers and high-pressure, high-temperature boilers: Annual internal inspection when construction permits; otherwise, as complete an inspection as possible; Annual external inspection while under pressure, if possible. Low-pressure boilers: a biennial certificate inspection. Pressure vessels: a biennial certificate inspection. Amusement attractions with low-pressure boiler and pressure vessel parts: annual certificate inspection. Nuclear vessels within the scope of this act shall be inspected and reported on such form (Section XI) with appropriate information as designated by the board. Model steam boilers (individually fabricated for noncommercial use, and primarily for demonstration, exhibition, or educational purposes, and not for profit): an annual external inspection and, to the extent possible, an internal inspection. Antique boilers: An annual internal inspection; Externally inspected while under pressure, if possible. Extended interval between internal inspections: the Board of Boiler Rules may extend the interval between inspections of certain power boilers to two years where: The boiler has internal continuous water treatment under the general supervision of a registered professional engineer having experience in the treatment of boiler water; The owner/user of such boiler keeps available for examination by the chief boiler inspector accurate records showing: The date and actual time such boiler is out of service and the reason or reasons therefor; Such chemical and physical analysis of samples of the boiler water taken at regular intervals of not more than 48 hours of operation, as well as adequately showing the condition of such water and any elements or characteristics thereof which are capable of producing corrosion or other deterioration of the boiler or its parts. Source: https://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select ### Statute citation chardonlabs.com says statute citation is **Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9**, as of 2026-08-05. > Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9. Authorized inspector types: Maryland accepts commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request. Inspection frequency: High-pressure boilers require annual internal inspections, where construction permits and annual external inspections are performed while under pressure. Low-pressure boilers require biennial certificate inspections. Source: https://www.chardonlabs.com/resources/commercial-boiler-inspection-regulations-by-state/ nationalboard.org says statute citation is **Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9, Boiler and Pressure Vessel Safety Act.**, as of 2026-08-05. > Power boilers and high-pressure, high-temperature boilers: Annual internal inspection when construction permits; otherwise, as complete an inspection as possible; Annual external inspection while under pressure, if possible. Low-pressure boilers: a biennial certificate inspection. Pressure vessels: a biennial certificate inspection. Amusement attractions with low-pressure boiler and pressure vessel parts: annual certificate inspection. Nuclear vessels within the scope of this act shall be inspected and reported on such form (Section XI) with appropriate information as designated by the board. Model steam boilers (individually fabricated for noncommercial use, and primarily for demonstration, exhibition, or educational purposes, and not for profit): an annual external inspection and, to the extent possible, an internal inspection. Antique boilers: An annual internal inspection; Externally inspected while under pressure, if possible. Extended interval between internal inspections: the Board of Boiler Rules may extend the interval between inspections of certain power boilers to two years where: The boiler has internal continuous water treatment under the general supervision of a registered professional engineer having experience in the treatment of boiler water; The owner/user of such boiler keeps available for examination by the chief boiler inspector accurate records showing: The date and actual time such boiler is out of service and the reason or reasons therefor; Such chemical and physical analysis of samples of the boiler water taken at regular intervals of not more than 48 hours of operation, as well as adequately showing the condition of such water and any elements or characteristics thereof which are capable of producing corrosion or other deterioration of the boiler or its parts. Source: https://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select ### Power boiler inspection interval chardonlabs.com says power boiler inspection interval is **annual internal inspections, where construction permits and annual external inspections performed while under pressure**, as of 2026-08-05. > Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9. Authorized inspector types: Maryland accepts commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request. Inspection frequency: High-pressure boilers require annual internal inspections, where construction permits and annual external inspections are performed while under pressure. Low-pressure boilers require biennial certificate inspections. Source: https://www.chardonlabs.com/resources/commercial-boiler-inspection-regulations-by-state/ nationalboard.org says power boiler inspection interval is **Annual internal inspection when construction permits; otherwise, as complete an inspection as possible; Annual external inspection while under pressure, if possible.**, as of 2026-08-05. > Power boilers and high-pressure, high-temperature boilers: Annual internal inspection when construction permits; otherwise, as complete an inspection as possible; Annual external inspection while under pressure, if possible. Low-pressure boilers: a biennial certificate inspection. Pressure vessels: a biennial certificate inspection. Amusement attractions with low-pressure boiler and pressure vessel parts: annual certificate inspection. Nuclear vessels within the scope of this act shall be inspected and reported on such form (Section XI) with appropriate information as designated by the board. Model steam boilers (individually fabricated for noncommercial use, and primarily for demonstration, exhibition, or educational purposes, and not for profit): an annual external inspection and, to the extent possible, an internal inspection. Antique boilers: An annual internal inspection; Externally inspected while under pressure, if possible. Extended interval between internal inspections: the Board of Boiler Rules may extend the interval between inspections of certain power boilers to two years where: The boiler has internal continuous water treatment under the general supervision of a registered professional engineer having experience in the treatment of boiler water; The owner/user of such boiler keeps available for examination by the chief boiler inspector accurate records showing: The date and actual time such boiler is out of service and the reason or reasons therefor; Such chemical and physical analysis of samples of the boiler water taken at regular intervals of not more than 48 hours of operation, as well as adequately showing the condition of such water and any elements or characteristics thereof which are capable of producing corrosion or other deterioration of the boiler or its parts. Source: https://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select ### Low-pressure boiler inspection interval chardonlabs.com says low-pressure boiler inspection interval is **biennial certificate inspections**, as of 2026-08-05. > Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9. Authorized inspector types: Maryland accepts commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request. Inspection frequency: High-pressure boilers require annual internal inspections, where construction permits and annual external inspections are performed while under pressure. Low-pressure boilers require biennial certificate inspections. Source: https://www.chardonlabs.com/resources/commercial-boiler-inspection-regulations-by-state/ nationalboard.org says low-pressure boiler inspection interval is **Low-pressure boilers: a biennial certificate inspection.**, as of 2026-08-05. > Power boilers and high-pressure, high-temperature boilers: Annual internal inspection when construction permits; otherwise, as complete an inspection as possible; Annual external inspection while under pressure, if possible. Low-pressure boilers: a biennial certificate inspection. Pressure vessels: a biennial certificate inspection. Amusement attractions with low-pressure boiler and pressure vessel parts: annual certificate inspection. Nuclear vessels within the scope of this act shall be inspected and reported on such form (Section XI) with appropriate information as designated by the board. Model steam boilers (individually fabricated for noncommercial use, and primarily for demonstration, exhibition, or educational purposes, and not for profit): an annual external inspection and, to the extent possible, an internal inspection. Antique boilers: An annual internal inspection; Externally inspected while under pressure, if possible. Extended interval between internal inspections: the Board of Boiler Rules may extend the interval between inspections of certain power boilers to two years where: The boiler has internal continuous water treatment under the general supervision of a registered professional engineer having experience in the treatment of boiler water; The owner/user of such boiler keeps available for examination by the chief boiler inspector accurate records showing: The date and actual time such boiler is out of service and the reason or reasons therefor; Such chemical and physical analysis of samples of the boiler water taken at regular intervals of not more than 48 hours of operation, as well as adequately showing the condition of such water and any elements or characteristics thereof which are capable of producing corrosion or other deterioration of the boiler or its parts. Source: https://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select ### Accepted inspector types chardonlabs.com says accepted inspector types is **commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request**, as of 2026-08-05. > Annotated Code of Maryland, Public Safety Article, Title 12, Subtitle 9. Authorized inspector types: Maryland accepts commissioned special inspectors from insurance companies. The Commissioner may also commission qualified owner company inspectors upon request. Inspection frequency: High-pressure boilers require annual internal inspections, where construction permits and annual external inspections are performed while under pressure. Low-pressure boilers require biennial certificate inspections. Source: https://www.chardonlabs.com/resources/commercial-boiler-inspection-regulations-by-state/ nationalboard.org says accepted inspector types is **Inspections made by inspectors employed by insurance companies (special inspectors) and commissioned by the division are accepted in lieu of inspections made by a deputy inspector.**, as of 2026-08-05. > Power boilers and high-pressure, high-temperature boilers: Annual internal inspection when construction permits; otherwise, as complete an inspection as possible; Annual external inspection while under pressure, if possible. Low-pressure boilers: a biennial certificate inspection. Pressure vessels: a biennial certificate inspection. Amusement attractions with low-pressure boiler and pressure vessel parts: annual certificate inspection. Nuclear vessels within the scope of this act shall be inspected and reported on such form (Section XI) with appropriate information as designated by the board. Model steam boilers (individually fabricated for noncommercial use, and primarily for demonstration, exhibition, or educational purposes, and not for profit): an annual external inspection and, to the extent possible, an internal inspection. Antique boilers: An annual internal inspection; Externally inspected while under pressure, if possible. Extended interval between internal inspections: the Board of Boiler Rules may extend the interval between inspections of certain power boilers to two years where: The boiler has internal continuous water treatment under the general supervision of a registered professional engineer having experience in the treatment of boiler water; The owner/user of such boiler keeps available for examination by the chief boiler inspector accurate records showing: The date and actual time such boiler is out of service and the reason or reasons therefor; Such chemical and physical analysis of samples of the boiler water taken at regular intervals of not more than 48 hours of operation, as well as adequately showing the condition of such water and any elements or characteristics thereof which are capable of producing corrosion or other deterioration of the boiler or its parts. Source: https://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select ## Source - https://www.chardonlabs.com/resources/commercial-boiler-inspection-regulations-by-state/ - https://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select Last verified: 2026-08-05. Review by: 2027-08-05. Part of [US boiler and pressure vessel inspection requirements by state](https://referencesource.org/boiler-inspection-requirements-by-state/).