SAFETY AND ENVIRONMENTAL CONSIDERATIONS continued
Use of hydrogen The other hazard that should be addressed is
the use and storage areas for fl ammable gases like hydrogen, as well as potentially toxic gases like hydrogen sulfi de or carbon monoxide. In National Fire Protection Association Code NFPA
only limited quantities are allowed to be used in restricted control areas like fumehoods, and that anything more than a cubic foot or two requires a thorough engineered installation requiring gas cabinets, dedicated purging and exhaust system scrubbers, as well as hazardous
than the MAQ for hydrogen in laboratories supplying hydrogen for instrumentation and/ or chemical reactions like hydrogenation.
There are four main areas required by NFPA 55 for these types of installations: fi re-resistance rating, ventilation, separation, and controls.
55, Compressed Gases and Cryogenic Fluids, specifi ed Maximum Allowable Quantities (MAQ) are defi ned specifi cally for hydrogen and for toxic or highly toxic gases. For most toxic or highly toxic gases, it is readily understood that
gas leak detection and shut-down capabilities.
However, when it comes to smaller installations of hydrogen in which outside storage and con- trol to line pressures of less than 150 psig are not available, it is not unusual to fi nd greater
There are four main areas required by NFPA 55 for these types of installations: fi re-resistance rating, ventilation, separation, and controls. Many laboratory staff and planners do not un- derstand that, once there is more than a single cylinder of hydrogen on a system or designated area, the level of these requirements is such that you are limited to either constructing a dedi- cated hydrogen room or having the cylinders and their controls in a gas cabinet. In NFPA 55, the MAQ for a specifi c use or storage area would seem to allow a large amount of hydrogen to be used or stored.
However, within those MAQ, there are limits that, once crossed, require higher fi re rating material, greater ventilation requirements, and strict implementation of separation distances. In general these requirements initiate when quantities exceed 250, 400, and 3500 cubic feet. Once the volume reaches 15,000 cubic feet, the area must be located in a detached building or outdoors.
1. Fire-resistance rating requirements set forth in NFPA 55:
a. Section 6.3.1.3.1 states that where fl ammable gases are stored or used in quantities in excess of 250 cubic feet, the area is to be separated from other occupancies by 1-hr rated construction.
b. Combustible material and hydrogen tanks must be separated by a 10-ft distance or a noncombustible wall that extends not less than 18 in. above and to the sides of the area used for combustible material.
c. Hydrogen tanks are to be separated from incompatible materials, e.g., oxygen, by a 20-ft distance or a noncombustible wall having a fi re resistance rating of at least 0.5 hr that extends not less than 18 in. above and to the sides of the cylinders.
Figure 3 – NFPA 55 compatible gas storage (separation). AMERICAN LABORATORY • 18 • SEPTEMBER 2014
d. Areas in which a hydrogen system is located are to be permanently placarded as follows: WARNING: HYDROGEN—FLAMMABLE GAS—NO SMOKING—NO OPEN FLAMES.
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