A gas cabinet is a ventilated, enclosed storage unit designed to safely house compressed gas cylinders used in laboratories, particularly those containing toxic, flammable, or highly reactive gases. Its primary function is to provide secondary containment by capturing leaks or releases and exhausting them through a dedicated ventilation system, thereby preventing hazardous gases from entering the laboratory space. By isolating gas cylinders and integrating engineering controls, gas cabinets play a critical role in protecting personnel, equipment, and the facility from gas-related hazards.
A properly designed gas cabinet system will fulfill the following objectives:
- Containment of hazardous gas in the event of leakage
- Maintenance of gas integrity
- Automatic shutoff of gas in the event of catastrophic failure
- Effective control of residual gas during cylinder changeout
Flammable Gas
Flammable gases are gases that, at 68° F or less at an absolute pressure of 14.7 psi, is ignitable at an absolute pressure of 14.7 psi when in a mixture of 13 percent or less by volume with air, or that has a flammable range at an absolute pressure of 14.7 psi with air of at least 12 percent, regardless of the lower limit. The gas is generally a U.S. Department of Transportation (“DOT”) Class 2.1 Flammable with a NFPA flammability rating of 4.
Corrosive Gas
Corrosive gases are gases that causes visible destruction of or irreversible alterations in living tissue by chemical action at the site of contact. The gas is generally a DOT Class 2.3 Poison with a NFPA health rating of 3 or 4.
Pyrophoric Gases
Pyrophoric gases are gases with an autoignition temperature in air at or below 130°F. The gas is generally a DOT Class 2.1 Flammable with a NFPA reactivity rating of 3.
Toxic Gas
Toxic gases are gases with a median lethal concentration (LC50) in air of more than 200 parts per million (ppm) but not more than 2,000 ppm by volume of gas or vapor. Examples of toxic gas are chlorine, hydrogen sulfide (H2S), and hydrogen fluoride (HF). A toxic gas is generally a DOT Class 2.3 Poison with a NFPA health rating of 3 or 4.
Highly Toxic Gas
Highly toxic gases are gasses that have a LC50 in air of 200 ppm or less by volume of gas or vapor. Examples of highly toxic gas are arsine, phosphine (PH3), and nitric oxide (NO). A highly toxic gas is generally a DOT Class 2.3 Poison with a NFPA health rating of 3 or 4.
A gas cabinet itself is designed to isolate gas cylinders from the surrounding environment. In doing so, it protects end users from the hazards associated with the different gas types. Gas cabinets are provided with self-closing access port(s) or windows of sufficient size that allow hand access to equipment controls and are provided with makeup air inlets that allow air circulation throughout the cabinet when the access port(s) or windows are closed.
In addition to the gas cabinet, extra safety features are often built into the overall system. Such components are considered based on the gas hazard type (flammable, toxic, pyrophoric, or highly toxic). Incorporating these components into the cabinet will serve as additional methods of protection for individuals working with and around hazardous gases.
Emergency Shut-Off Valve
Quickly stops flow of gases in the event of leak downstream and can be activated automatically by gas detection system or manually by emergency stop button.
Excess Flow Control
Halts flow of gas when abnormal (high) glow levels occur, which are typically indicative of a leak in the piping.
Exhaust Alarm
Alerts end users when negative pressure or exhaust flow to cabinet is lost; also shuts down gas flow to ensure operators aren’t exposed to potential leaks that may occur during loss of negative pressure.
Gas Detection System
Provides notification of flammable, toxic, highly toxic, or pyrophoric gas concentrations in atmosphere. The alarms activate before dangerous levels are reached (LFL, PEL).
Purge System
Used to flush residue of process gas out to vent, helps to ensure that operator is not exposed to hazardous gas during cylinder changeout.
Vacuum Drive
Used in conjunction with purge system as a means of extracting hazardous gases from delivery equipment.
Hazardous/Toxic Gas Cabinets
Designed for high-risk gases, these often feature automatic purging systems, gas sensors, and sprinklers for safety.
Flammable Gas Cabinets
Specifically engineered to store combustible gases safely, often meeting stringent fire-resistance standards.
Lecture Bottle Cabinets
Smaller cabinets designed for storing smaller-sized, portable "lecture bottle" gas cylinders.
Valve Manifold Boxes (VMB)
Specialized cabinets that manage the distribution of gases from cylinders to tools, allowing for better control.
Leaker Cabinets
Specialized enclosures used specifically to contain and neutralize leaking or damaged cylinders.
Gas Cylinder Storage Cabinets (Vertical/Horizontal)
General-purpose storage for industrial gases (nitrogen, oxygen, propane) that can be configured to hold cylinders upright or on their side.
