1. NFPA 45, Chapter 8
  2. NFPA 99, Chapter 4
  3. NFPA 704, Chapter 2
The Guide applies to all UNC-Chapel Hill facilities, including leased properties. It covers the design of storage for compressed gas cylinders. Note that there are numerous regulations governing the proper use of compressed gas cylinders; use is not addressed by the Guide, as it is a work practices issue, rather than design feature.
Laboratory design shall include a storage area for cylinders of compressed gases where:

  1. They are protected from external heat sources such as flame impingement, intense radiant heat, electric arc, or high temperature steam lines.
  2. They are in a well-protected, well-ventilated, dry location, at least 20 feet from highly combustible materials.

NFPA 99, 4-3.1.1.2

Design features which are prohibited: Unventilated enclosures such as lockers and cupboards.

Work practice issues: Oxygen cylinders shall not be stored near highly combustible materials, especially oil or grease, or near any other substance likely to cause or accelerate fire.

Restraint Systems

Laboratory design shall include restraints for the storage of cylinders greater than 26 inches tall; the restraint system shall include at least 2 restraints (made of noncombustible materials), which are located at one-third and two-thirds the height of the cylinder.

NFPA 45, 8-1.5
NFPA 99, 4-3.1.1.2.3

A restraint system of chains, metal straps, or storage racks provides a reliable method of securing gas cylinders. Chains or a metal strap at the bottom and top one third of each cylinder provides protection against tipping and falling. [Work Practice Note: When compressed gas cylinders in service, they shall be adequately secured by chains, metal straps, or other approved materials, to prevent cylinders from falling or being knocked over.]

The purchase and installation of compressed gas cylinder securing systems must be subject to review and approval of EHS.

Gas cylinder securing systems should be anchored to a permanent building member or fixture.

Provisions shall be made for securing cylinders that are delivered to locations outside of the laboratory.

Laboratory design shall incorporate storage capabilities of compressed gas cylinders of toxic and highly toxic gases per the following table. The number of lecture bottle cylinders [approximately 5 cm x 33 cm (2 in. x 13 in.)] shall be limited to 25. See Table 6-1. Also, review the International building and fire codes for other limitations.

Table 6-1: Flammable or Oxidizing Gases Liquefied Flammable Gases with Health Hazard Rating of 3
Cylinder Description Flammable or Oxidizing Gases Liquefied Flammable Gases Gases with Health Hazard Rating of 3 or 4
Sprinklered Space Non-Sprinklered Space Sprinklered Space Non-Sprinklered Space Non-Sprinklered or Sprinklered Space
Maximum number of cylinders per 46.5 m2 (500 ft.2) or less 6 3 3 2 3

Storage Systems

Laboratory design shall include one of the following storage systems for toxic and highly toxic compressed gas cylinders:

  1. ventilated gas cabinets/exhausted enclosures/ laboratory fume hoods; or
  2. separate ventilated gas storage rooms without other occupancy or use, which has explosion control.

When gas cabinets or exhausted enclosures are provided they shall (be):

  1. located in a room or area which has independent exhaust ventilation;
  2. operate at negative pressure in relation to the surrounding area;
  3. have self-closing limited access parts or noncombustible windows to provide access to equipment controls, with an average face velocity of at least 200 fpm and with a minimum of 150 fpm at any part of the access port or window;
  4. connected to an exhaust system;
  5. have self-closing doors and is constructed of at least 0.097 inch (12 gauge) steel;
  6. internally sprinklered;
  7. anchored;
  8. contain not more than 3 cylinders per gas cabinet, except where cylinder contents are 1 pound net or less, in which case gas cabinets may contain up to 100 cylinders.

When separate gas storage rooms are provided they shall:

  1. Operate at a negative pressure in relation to the surrounding area;
  2. Direct the exhaust ventilation to an exhaust system.

Treatment

Treatment systems for the exhaust of toxic and highly toxic gases must be reviewed and approved by EHS.

EHS reviews treatment systems to ensure they are compliant and are consistent.

Emergency Power

Emergency power shall be provided for exhaust ventilation, gas-detection systems, emergency alarm systems, and temperature control systems.

Detection System

A continuous gas detection system shall be provided to detect the presence of gas at or below the permissible exposure limit or ceiling limit. The detection system shall initiate a local alarm and transmit a signal to a constantly attended location. Activation of the monitoring system shall automatically close the shut-off valve on toxic and highly toxic gas supply lines to the system being monitored.

An approved supervised smoke detection system shall be provided in rooms or areas where highly toxic compressed gases are stored indoors.

Security

Storage areas shall be secured against unauthorized entry.

Enclosures such as 1-hour interior and exterior rooms (detailed below) must be provided for supply systems cylinder storage or manifold locations for oxidizing agents such as oxygen and nitrous oxide. Such enclosures must be constructed of an assembly of building materials with a fire-resistive rating of at least 1 hour and must not communicate directly with anesthetizing locations.

NFPA 99, Sections 4-3.1.1.2(a).2

Other nonflammable (inert) medical gases may be stored in the enclosure. Flammable gases shall not be stored with oxidizing agents. Storage of full or empty cylinders is permitted. Such enclosures shall serve no other purpose.

A 1-hour exterior room shall be a room or enclosure separated form the rest of the building by not less than 1-hour-rated fire-resistive construction. Openings between the room or enclosure and interior spaces shall be smoke-and draft-control assemblies having no less than a 1-hour fire-protection rating. Rooms shall have at least one exterior wall provided with at least two vents. Each vent shall not be less than 36 square inches in area. One vent shall be within 6 inches of the floor and one shall be within 6 inches of the ceiling. Containers of medical gases shall be provided with at least one fire sprinkler to provide container cooling in case of fire.

When an exterior wall cannot be provided for the room, automatic sprinklers shall be installed within the room. The room shall be exhausted through a duct to the exterior. Makeup air to the room shall be taken from the exterior. Both separate air streams shall be enclosed in a 1-hour-rated shaft enclosure from the room to the exterior. Approved mechanical ventilation shall be in accordance with the California Mechanical Code and provided at a minimum rate of 1 cubic foot per minute per square foot of the room area.

Medical gas system cabinets shall be in accordance with the following:

  1. Operated at a negative pressure in relation to surrounding area,
  2. Provided with self-closing, limited-access ports or noncombustible windows to give access to equipment controls. The average velocity of ventilation at the face of access ports or windows shall not be less than 200 feet per minute, with a minimum of 150 feet per minute at any point of the access port or window,
  3. Connected to an exhaust system,
  4. Provided with a self-closing door,
  5. Constructed of not less than 0.097-inch (12 gage) steel, and
  6. Internally sprinklered