Abstract: A modular hyperbaric chamber for treatment of at least one patient that includes at least one spacer module having a first flange and a second flange. The spacer module may be formed from a plurality of sections, with each section including opposing lip portions to form air-tight junctions. A first half cylinder module includes a first peripheral contact edge for releasable sealed connection to the first flange of the spacer module. Similarly, a second half cylinder module includes a second peripheral contact edge, for releasable sealed connection to the second flange of the spacer module. An access door, formed in at least one of the half cylinder modules provides access to the interior of the chamber. The overall size of a hyperbaric chamber may be conveniently increased by inserting additional spacer modules between the half cylinder modules.