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Safety

Transport & Storage

In the clinical laboratory, compressed gas cylinders act as potential kinetic energy bombs. A standard cylinder can be pressurized up to 2,200 psi. If the valve stem is sheared off due to a fall, the escaping gas can propel the cylinder through concrete walls at speeds comparable to a missile. Consequently, the transport and storage of these vessels are governed by rigid physical safety protocols designed to maintain the structural integrity of the container and the valve

Transport Protocols

Moving a cylinder from the loading dock to the laboratory (e.g., bringing a CO2 tank to a Microbiology incubator) is the period of highest risk. Hand-carrying or rolling cylinders along the floor is strictly prohibited

The Valve Protection Cap

The most critical safety device on a cylinder is the threaded metal cap

  • Mandatory Usage: The cap must be screwed on hand-tight whenever the cylinder is not actively connected to a regulator. This applies even if the cylinder is “Empty.”
  • Function: The cap protects the brass valve stem. If a capped cylinder falls, the impact is absorbed by the cap. If an uncapped cylinder falls and strikes the valve, the valve can shear, releasing the pressurized contents instantly
  • Lifting Constraint: Never lift a cylinder by the cap. The threads may be loose, causing the heavy cylinder to fall on the operator’s feet

The Cylinder Hand Truck

  • Appropriate Equipment: Cylinders must be moved using a hand truck (dolly) specifically designed for gas cylinders. These carts feature a curved back and a securing chain
  • Technique
    1. Ensure the valve cap is secure
    2. Slightly tilt the cylinder to slide the cart’s base plate underneath
    3. Secure the chain: immediately. Never move the cart without the chain engaged
    4. Move at a walking pace
  • Prohibitions: Never drag, slide, or roll a cylinder horizontally. Never use a standard flatbed cart where the cylinder could roll off

Elevator Transport (Unaccompanied Transport)

Transporting gases in elevators poses an asphyxiation risk. If the elevator stalls and the cylinder begins to leak, the confined space will quickly become oxygen-deficient or toxic

  • Protocol: Place the secured cylinder in the elevator. Prevent public access. Send the elevator to the destination floor. A second person must be waiting at the destination floor to receive it. No personnel should ride in the elevator with a compressed gas cylinder.

Storage Requirements

Once in the laboratory, cylinders must be stored in a manner that prevents tipping and protects them from environmental extremes

Securing & Restraints

  • The “Two-Point” or “2/3rds” Rule: Cylinders must be secured to a wall, a permanent bench fixture, or a heavy cylinder stand using non-combustible chains or heavy-duty straps. The chain should be placed approximately 2/3 of the way up the cylinder body (above the center of gravity) to prevent tipping
  • Individual Restraint: Ideally, each cylinder should have its own chain. “Gang chaining” (looping one long chain around a group of cylinders) is less secure, as removing one cylinder creates slack that endangers the others

Environmental Conditions

  • Temperature: Cylinders must be stored away from heat sources (radiators, drying ovens, autoclaves). According to the Ideal Gas Law (PV=nRT), increasing temperature increases pressure. If the internal pressure exceeds the cylinder’s rating, the safety relief valve may rupture, venting the gas. Temperatures should not exceed 125°F (52°C)
  • Ventilation: Storage areas must be dry and well-ventilated to prevent corrosion of the metal tank and to allow leaking gases to dissipate
  • Egress: Cylinders must never be stored in hallways, stairwells, or directly in front of exit doors. They must not obstruct evacuation routes

Inventory Management

  • Status Tagging: Cylinders should be clearly tagged as “Full,” “In Use,” or “Empty.”
  • Separation: “Full” and “Empty” cylinders should be physically separated. This prevents a laboratory scientist from accidentally hooking up an empty tank to a critical life-support instrument or an automated analyzer during an emergency
  • Stock Rotation: Use the “First-In, First-Out” (FIFO) method. Old cylinders can suffer from valve corrosion or seal degradation

Segregation of Incompatibles (The 20-Foot Rule)

Chemical hazards dictate how cylinders are arranged relative to one another. Mixing incompatible classes of gases can lead to catastrophic fires

Oxidizers vs. Flammables

  • The Hazard: Oxidizers (Oxygen, Nitrous Oxide) greatly accelerate combustion. Flammables (Hydrogen, Acetylene, Propane) provide the fuel. Storing them side-by-side creates a high risk of explosion if a leak occurs
  • The Regulation: Oxygen cylinders must be separated from fuel-gas cylinders by a minimum distance of 20 feet (6.1 meters)
  • The Exception: If a 20-foot separation is not physically possible in a small lab, they must be separated by a non-combustible fire wall (fire barrier) at least 5 feet high with a fire-resistance rating of at least one-half hour
  • In-Use Exception: This separation rule applies to storage. It does not apply to cylinders that are currently connected to an instrument (e.g., an Atomic Absorption Spectrophotometer using Acetylene and Air/Oxygen) for active use

Regulator Safety

The regulator is the interface between the high-pressure cylinder and the low-pressure laboratory instrument

  • CGA Fittings: The Compressed Gas Association (CGA) assigns unique connector geometries to different gases to prevent cross-connections
    • Inert/Oxidizers: Typically use right-hand threads (righty-tighty)
    • Flammables: Often use left-hand threads (lefty-tighty) and have a distinct “notch” cut into the nut
  • The “No Force” Rule: If a regulator does not screw on easily by hand, it is the wrong regulator. Never force it with a wrench
  • Opening the Valve: When opening a cylinder:
    1. Stand to the side of the regulator, never directly in front of the pressure gauge faces (in case the glass blows out)
    2. Open the valve slowly. Rapid opening can cause a sudden compression of gas in the regulator, generating heat that can ignite internal seals (Adiabatic Compression)