HyperbaricStore guide
PVHO-1 and Hyperbaric Chamber Safety
ASME PVHO-1 is the safety standard written specifically for pressure vessels that contain people while under pressure. That makes it one of the most important standards to understand when evaluating a hyperbaric chamber, but it is not a shortcut around the rest of the project’s code and permitting work.
ASME currently lists the 2023 edition of PVHO-1 — Safety Standard for Pressure Vessels for Human Occupancy. Standards are updated and adopted differently across projects, so confirm the edition named by the engineer, purchaser, and authority having jurisdiction before design or fabrication.
PVHO-1 is about the pressure vessel and its human-occupancy hazards. NFPA 99 is about the hyperbaric facility and its surrounding systems. A compliant project may need both.
What PVHO-1 covers
ASME defines a PVHO as a pressure vessel that encloses a human being within its pressure boundary while it is under an internal or external pressure differential exceeding 2 psi. The standard provides requirements for the design, fabrication, inspection, testing, marking, and stamping of PVHOs. It also addresses the design, fabrication, inspection, testing, cleaning, and certification of piping systems for PVHOs.
Examples include decompression and recompression chambers, medical hyperbaric chambers, diving bells, personnel transfer capsules, submersibles, and high-altitude chambers. The project team still has to determine whether a specific product and use fall within the standard and what other codes apply.
What a manufacturer must demonstrate
PVHO-1 is not satisfied by a product label alone. The manufacturer and design team should be able to connect the finished vessel to a controlled body of technical evidence:
- Design basis: intended use, occupancy, pressure range, cycles, materials, temperature, and applicable load cases.
- Pressure boundary: calculations, drawings, dimensions, openings, penetrations, closures, and details that protect the integrity of the vessel.
- Human-occupancy components: viewports, doors, locks, seals, internal fittings, communication systems, and emergency provisions as applicable to the design.
- Materials and joining: traceability, welding or brazing procedures, personnel qualifications, heat treatment, and repair controls where required.
- Inspection and examination: examinations, acceptance criteria, inspector involvement, and records retained in the vessel’s data book.
- Testing: pressure, leak, functional, and other tests required by the standard and the approved design.
- Marking and certification: nameplate, serial number, pressure information, documentation, and any required stamp or certification statement.
PVHO-1, ASME BPVC, and NFPA 99: how they fit together
| Reference | Primary question | Typical project owner |
|---|---|---|
| PVHO-1 | Is the pressure vessel for human occupancy designed, built, inspected, tested, and documented to the PVHO safety standard? | Manufacturer, design engineer, Authorized Inspector or qualified inspector |
| ASME BPVC | Does the manufacturer hold the applicable authorization and build within the selected Boiler and Pressure Vessel Code scope? | Manufacturer and ASME certification program |
| NFPA 99 | Does the chamber installation and facility address the electrical, fire, pressure, gas, and operational hazards required by the adopted facility code? | Owner, design team, fire/building/health AHJ |
There can be overlap, and the exact division of responsibility depends on the project and jurisdiction. Treat the table as a starting map, then document the governing requirements in the project specifications.
Questions to ask before purchasing a chamber
- Which edition of PVHO-1 is the chamber designed and documented to meet?
- Which pressure-vessel code or certification program is used in addition to PVHO-1?
- What are the design pressure, operating pressure, pressure cycles, occupancy, and intended service conditions?
- Who performed the design review and independent inspection, and what records are supplied with the vessel?
- How are viewports, closures, penetrations, piping, emergency systems, and maintenance intervals addressed?
- What testing and inspection is required after installation, relocation, repair, or alteration?
- Which local permits, registrations, fire reviews, medical-gas requirements, and facility standards apply at the destination?
Existing chambers and lifecycle safety
A chamber’s original documentation matters throughout its service life. Before relocating, modifying, repairing, or returning an older chamber to service, preserve the nameplate and serial number, locate the original data book, review inspection and repair history, and have the proposed work evaluated by the manufacturer or a qualified pressure-vessel professional. Do not assume that a new test or a visual inspection alone establishes compliance with the original design basis.