Space and access

A chamber has three sets of dimensions and buyers usually only see one. There is the internal space the occupant uses, the external footprint the room has to hold, and the service dimension — the clearance the equipment needs around it to be opened, maintained and repaired. The third one is the one that turns a workable room into an unworkable one, and it is published far less often than the first two.

Published dimensions, and the gap between internal and external

Sechrist publishes all three families of its monoplace H-series in full, which makes it a useful worked example even if you are buying something else entirely:

Note the relationship. Going from a 32.50 in to a 41.00 in internal diameter — an 8.5 in gain inside — costs 10.25 in of external width and 1,470 lb of weight. Internal comfort is bought with external footprint and floor loading at a distinctly unfavourable exchange rate, which is why "get the biggest one that fits" is bad advice unless you have checked the floor as well as the floor plan.

For fabric chambers the published figures are the chamber's own dimensions: the Summit to Sea Grand Dive is published as 40 in × 90 in, weighing approximately 55 lb for the chamber alone (retailer specification). That does not include the compressors, the concentrator, or the space a person needs to get in and out, and it is a footprint on the floor rather than a frame you walk around.

The service dimension, which almost nobody asks about

Sechrist's 3600H installation diagram shows a service dimension of 193.0 in — about 4.9 m (Sechrist H-series specifications). The chamber itself is 106 in long. The service requirement is therefore nearly twice the chamber's length, because the gurney and internal assembly have to withdraw fully from the shell for service.

This is the single most useful number on this page. A room that is 12 ft long will hold a 106 in chamber with room to walk past it, and will not allow that chamber to be serviced without moving it. If the chamber has to be moved out of the room every time it needs internal service, on a floor and through a doorway that were only checked for the delivery, you have built a recurring problem into the installation.

Floor loading is a structural question, not a rug question

NFPA 99 Chapter 14 states that the foundation "shall be designed to support the chamber and all associated equipment" (NFPA 99, 2015 edition, clause 14.2.1.1.9). UHMS puts the practical version in its FAQ: the floor must be able to carry the weight, and it references an indentation rating for flooring under chamber loads (UHMS standards and codes FAQ).

Do the arithmetic for your own case rather than trusting an impression. A 3,500 lb 4100H (Sechrist specifications) with a 700 lb occupant limit is 4,200 lb before compressors, concentrators or an operator standing beside it. Distributed across a 107 × 67.75 in footprint that is a modest average pressure, but chamber loads are not distributed evenly — they land on cradles or feet, which is exactly why the indentation question exists and why point loads matter more than the average. On a wooden joisted floor, upstairs, or over a basement, this is a question for a structural engineer, and the cost of asking is trivial against the cost of not asking.

Getting it into the room

The path matters as much as the destination. Measure, in order: the exterior door, every interior doorway on the route, every corridor width and every turn, stair widths and landing dimensions, ceiling heights including any soffit or light fitting, and lift internal dimensions and rated capacity if a lift is involved. Then compare against the chamber's crated dimensions, which are larger than the published external dimensions and which the manufacturer must supply.

A 106 in long, 61 in wide chamber (3600H) does not turn a tight 90-degree corridor corner, and no amount of goodwill on delivery day changes that. Where the path does not work, the options are removing a window or door frame, craning through an opening, or choosing a different chamber — and all three are decisions to make before the deposit, not on the day.

Room conditions the equipment expects

Chambers publish operating environment limits and those limits are room requirements. The Sechrist H-series specifies an operating temperature range of 50–100 °F and relative humidity of 30–90% at 77 °F (Sechrist H-series specifications). UHMS reports that Sechrist recommends a room temperature of 68–74 °F, notes that below 50 °F seal performance is affected, and that above 100 °F is beyond the acrylic's design conditions (UHMS standards and codes FAQ).

That rules out a number of rooms people would otherwise choose: an uninsulated garage in a cold climate, a Florida outbuilding without cooling, a loft that sits above 100 °F in summer. It also rules out putting the concentrator somewhere hot — its published operating range is 41–95 °F (AirSep NewLife Intensity 10 specifications), and it is itself a heat source at 590 W.

Humidity has a safety dimension as well as an equipment one: ">60 percent humidity will nearly eliminate static potential," per UHMS, while the same FAQ calls for antistatic procedures whenever chamber atmospheres exceed 23.5% oxygen (UHMS). So the room's humidity target sits between the equipment's 30–90% tolerance and a static-control preference for the upper part of that range.

Exclusive use, for commercial installations

If the chamber goes into a building under NFPA 99 Chapter 14 as a Class A or Class B chamber, "the room or rooms in which the chamber(s) is located shall be for the exclusive use of the hyperbaric operation" (NFPA 99, 2015 edition, clause 14.2.1.1.7; applicable edition per your authority having jurisdiction). Combined with the service dimension above, that means a commercial room has to be sized for the chamber plus its full service withdrawal plus its ancillary equipment, and cannot borrow adjacent space for storage. Rooms are routinely specified too small on exactly this point.

A room checklist you can measure today

• Chamber external dimensions and crated dimensions, from the manufacturer.
• Service withdrawal dimension from the installation drawing.
• Every doorway, corridor, turn, stair and lift on the delivery path.
• Floor construction and, where relevant, a structural opinion on point loads.
• Room temperature range across the year, against the published operating range.
• Room humidity range, against both the equipment range and static control.
• Where the compressor and each concentrator will physically sit, and their heat output.
• For commercial installations: NFPA 99 class, exclusive-use status, and suppression requirements.

Nothing on that list requires a specialist to start. Every item on it is cheaper to check now than after a chamber is on a truck. The pre-install checklist collects this together with the electrical, ventilation and freight items in one place.