International Building Code Section 420

International Building Code 420.6.1


System design. The flammable gas-detection
system shall be listed for use with hydrogen and any other
flammable gases used in the room. The gas detection system
shall be designed to activate when the level of flammable
gas exceeds 25 percent of the lower flammability limit
(LFL) for the gas or mixtures present at their anticipated
temperature and pressure.

International Building Code 420.6.3

Failure of the gas detection system. Failure of
the gas detection system shall result in activation of the
mechanical ventilation system, cessation of hydrogen generation
and the sounding of a trouble signal in an approved

International Building Code 420.1

General. When required by the International Fire
Code, hydrogen cutoff rooms shall be designed and constructed
in accordance with this section.

International Building Code 420.2

Definitions. The following words and terms shall,
for the purposes of this chapter and as used elsewhere in this
code, have the meanings shown herein.
piping, devices and apparatus designed to generate, store, contain,
distribute or transport a nontoxic, gaseous hydrogen-containing
mixture having at least 95-percent hydrogen gas by
volume and not more than 1-percent oxygen by volume. Gaseous
hydrogen systems consist of items such as compressed
gas containers, reactors and appurtenances, including pressure
regulators, pressure relief devices, manifolds, pumps, compressors
and interconnecting piping and tubing and controls.
HYDROGEN CUTOFF ROOM. A room or space that is
intended exclusively to house a gaseous hydrogen system.

International Building Code 420.3

Location. Hydrogen cut-off rooms shall not be
located below grade.

International Building Code 420.6

Gas detection system. Hydrogen cutoff rooms shall
be provided with an approved flammable gas-detection system
in accordance with Sections 420.6.1 through 420.6.3.

International Building Code 420.7

Explosion control. Explosion control shall be provided
in accordance with Chapter 9 of the International Fire

International Building Code 420.8

Standby power. Mechanical ventilation and gas
detection systems shall be connected to a standby power system
in accordance with Chapter 27.

International Building Code 420.4.1.1

Ventilation alternative. When an exhaust
system is used in lieu of the interlock system required by
Section 420.4, exhaust ventilation systems shall operate
continuously and shall be designed to operate at a negative
pressure in relation to the surrounding area. The
average velocity of ventilation at the face of the door
opening with the door in the fully open position shall not
be less than 60 feet per minute (0.3048 m/s) with a minimum
of 45 feet per minute (0.2287 m/s) at any point in
the door opening.

International Building Code 420.4.2

Windows. Operable windows in interior walls
shall not be permitted. Fixed windows shall be permitted
when in accordance with Section 715.

International Building Code 420.4

Design and construction. Hydrogen cutoff rooms
shall be classified with respect to occupancy in accordance
with Section 302.1 and separated from other areas of the build-
ing by not less than 1-hour fire barriers or as required by Section
508.2 or 508.3 as applicable.

International Building Code 420.5

Ventilation. Cutoff rooms shall be provided with
mechanical ventilation in accordance with the applicable provisions
for repair garages in Chapter 5 of the International
Mechanical Code.

International Building Code 420.6.2

Operation. Activation of the gas detection system
shall result in all of the following:
1. Initiation of distinct audible and visual alarm signals
both inside and outside of the cutoff room.
2. Activation of the mechanical ventilation system.

International Building Code 420.4.1

Opening protectives. Doors within such fire
barrier walls, including doors to corridors, shall be
self-closing in accordance with Section 715. Interior door
openings shall be electronically interlocked to prevent operation
of the hydrogen system when doors are opened or ajar
or the room shall be provided with a mechanical exhaust
ventilation system designed in accordance with Section