Every measurement problem we get called about is the same problem. Somebody measured the door. Nobody measured the opening. Those are two different numbers, and the gap between them is usually about two inches — which is often exactly the margin that was never there in the first place.
The way to get this right is the way the federal accessibility standard does it. Under the 2010 ADA Standards, a door opening is measured “between the face of the door and the stop, with the door open 90 degrees” and must give a clear width of 32 inches minimum; an opening more than 24 inches deep has to give 36 inches (2010 ADA Standards for Accessible Design, 404.2.3). That is the geometry you are actually working with: the leaf sitting in the way, the stop, and in an altered opening a latch-side stop that is allowed to eat another 5/8 inch. A nominal 36-inch door does not hand you 36 inches. It hands you the clear opening, and you have to go and find out what that is with a tape.
We are not saying your house is subject to the ADA. We are saying the standard describes the only measurement that matters, and it is the one people skip.
On a rigid chamber the numbers do not even come close
Once you have the clear opening written down, compare it with what the manufacturer published to FDA. Sechrist's H-series clearance gives external widths of 44.50 inches for the 3300H and 3600H and 46.75 inches for the 4100H, all of them 106 inches long, weighing 2,030 lb, 2,220 lb and 3,500 lb respectively (FDA 510(k) K140559). Set 44.50 against a 32-inch clear opening and the conversation stops being about doorways. It becomes a question about which door leaf comes off its hinges, whether the frame comes out, which wall the chamber goes through instead, or whether the thing is rigged in before a wall is closed up. All of those are answerable. None of them are answerable on delivery morning with a truck idling outside.
We install and service this equipment and sell chambers from several manufacturers, including Prestige Hyperbaric. The measurements above are the manufacturers' own published figures, and we would rather you check them against your room before anyone quotes you.
Two doorways get confused with each other
There is a second doorway in this conversation and it belongs to the chamber. Multiplace clearances publish it directly: the HyperOx 101 lists a doorway opening of 30 × 60 inches clear on a chamber that is 72 inches wide, 88 inches high, 16 ft 6 in long and weighs 11,200 lb (FDA 510(k) K053498). When a spec sheet says “doorway,” read twice. That figure tells you how a person gets into the chamber. It tells you nothing about how the chamber gets into the building.
Soft chambers move the problem rather than removing it
A fabric chamber walks through a normal door because it arrives folded. The Revitalair 430+ clearance describes a cylinder 900 mm in diameter and 1,850 mm long, weighing 62 lb, that packs into a transport box, with the compressor living in a separate cabinet (FDA 510(k) K220290). The catch is the second measurement, the one taken after assembly: 900 mm is 35.4 inches of diameter that has to sit somewhere with room to walk around it, and an inflated chamber does not turn a corner or pass back through a 32-inch opening. People who measured for delivery and not for the finished installation end up assembling in the wrong room and taking it apart again.
You will not always find crate dimensions to check against. OxyHealth's own product page for the Fortius 420 publishes an operating pressure, a voltage requirement and the compressor type, but no chamber dimensions and no weight (OxyHealth Fortius 420). When that happens, ask the seller for the crated dimensions in writing before the freight is booked, and get them on the bill of lading rather than in a phone call.
One more thing, if you are cutting an opening
If your plan involves adding or widening a door into the chamber room, find out what kind of assembly that door has to be before anyone orders one. NFPA 99 requires that connecting doors through common walls of contiguity to a Class A or Class B chamber room be at least B-label 1½-hour fire doors, and it also requires the room to be for the exclusive use of the hyperbaric operation while it is in use (NFPA 99 (2015), 14.2.1.1.6 and 14.2.1.1.7). A rated door is a different lead time and a different price from a hollow-core one.
Chapter detail on room geometry lives in Space and access, and the delivery-day sequence is in Freight and delivery.
Sources in this note
- 2010 ADA Standards for Accessible Design, 404.2.3 Clear Width — ada.gov
- FDA 510(k) K140559, Sechrist H-series external dimensions and weights — accessdata.fda.gov
- FDA 510(k) K053498, HyperOx 101 doorway opening and dimensions — accessdata.fda.gov
- FDA 510(k) K220290, Revitalair 430+ construction, dimensions and weight — accessdata.fda.gov
- OxyHealth Fortius 420 product specifications — oxyhealth.com
- NFPA 99 (2015) Chapter 14, Hyperbaric Facilities — chapter PDF