Chapter 13
GAS SAFETY

Contents

Approved by Kurt Ettinger
Revised 11/13

NOTE:
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13.1 Policy

The Gas Safety Program at Berkeley Lab identifies precautions to prevent injuries, property damage, and disruption to operations caused by leaks of compressed gas and over-pressurizations. Types of injuries and accidents that will be controlled include:

13.2 Scope

This program applies to the storage, use, and handling of gases in pressurized portable containers and gas systems. The primary focus of this program is on single-gas uses and systems. Additional requirements apply to:

13.3 Applicability

All Berkeley Lab employees, affiliates, and subcontractors who will order, handle, or dispose of gases

13.4 Exceptions

None

13.5 Roles and Responsibilities

Role

Responsibilities

Principal Investigator/Supervisor

The principal investigator or gas-use supervisor has primary responsibility for gas-use safety and implementation of all provisions of this chapter, including:

  • Activity Hazard Documents (AHDs)
  • Safety Notes
  • Training
  • Equipment and controls implementation, maintenance, and inspections
  • Request for gas pre-purchase approval, when required
  • Self-assessment inspections

EHSS — Industrial Hygiene Group

Provides an Environment, Health, Safety, and Security (EHSS) hazard-evaluation and code-compliance coordination role related to fire, life-safety, pressure, health, and oxygen-deficiency gas hazards, which includes:

  • Helping the gas user evaluate hazards and determine appropriate controls
  • Evaluating and approving purchases of gases that require pre-purchase approval
  • Reviewing new gas-use controls and designs (i.e., as part of AHD reviews), facilities projects, and required pre-gas purchases
  • Determining health-hazard classifications; required engineering controls and/or physiological warning property ratings to previously unclassified health-hazard gases, dilute gases, and gas mixtures
  • Periodically auditing gas uses as one component of the EHSS Integrated Functional Appraisal Program
  • Administering and maintaining the Gas, Pressure Safety, and Fire Protection programs. Pressure safety responsibilities are described in Chapter 7, Pressure Safety and Cryogenics.

EHSS — Fire Department

  • Monitors and responds to alarms transmitted via the fire alarm system or emergency telephone number system
  • Evaluates and issues permits for welding, cutting, and other hot work operations

Mechanical Engineering

  • Pressure-safety responsibilities are described in Chapter 7.

Facilities Department — Maintenance & Operations

  • Assists in the selection, installation, and startup of maintainable and reliable facilities safety systems that support gas-use operations
  • Through the Regulator Shop, assembles gas systems and provides, inspects, repairs, and/or rebuilds many commonly used gas-system components when requested
  • Manages gas-detector maintenance services for detector users who request service
  • Maintains an updated inventory of all gas detectors

Facilities Department — Technical Services

  • Manages gas supplier subcontracts for all compressed or liquefied gases. The gas subcontractors:
    • Receive gas orders from Berkeley Lab gas users, provide gases from gas suppliers, deliver gas cylinders to gas requestors, pick up cylinders from gas requestors, and return cylinders to gas suppliers. For return of high-hazard and specialty gases, regardless of vendor, contact Procurement at ext. 4513.
    • Screen gas purchase requests and ensure that requests that require pre-purchase approval are not ordered
  • Provides services related to higher-hazard and specialty gases:
    • Screens gas purchase requests and ensures that requests that require pre-purchase approval are approved by EHSS Field Support

 

13.6 Definitions

Term

Definition

 CFC

California Fire Code

 Control area

A space bounded by not less than a one-hour fire-resistive occupancy separation within which exempt amounts of hazardous materials may be stored, dispensed, handled, or used, as defined in the CFC

 Corrosive gas

A gas that can cause visible destruction of, or irreversible alterations in, living tissue (e.g., skin, eyes, or respiratory system) by chemical action

DOT

U.S. Department of Transportation

Exhausted enclosure

A gas cabinet, lab hood, or enclosed compartment connected to an approved negative-pressure exhaust duct system

EFV

Excess Flow Valve

Flammable gas

A gas that can be ignited in air

Compressed gas

A material shipped in a compressed-gas cylinder that acts as a gas upon release at normal temperature and pressure or is used or handled as a gas

Gas cabinet

An exhausted enclosure for storage or use of gas cylinders that meets the requirements specified in this chapter

Hazardous gas

A gas that is included in one or more of the following hazard categories: corrosive, flammable, health hazard, oxidizer, pyrophoric, reactive, or toxic

Hazardous-gas detection system

A fixed system used to detect the presence of hazardous gas at potentially unsafe levels

Health-hazard gas

Described in this chapter’s Work Process D, Health-Hazard Gases

IDLH

Immediately dangerous to life and health. IDLH is a maximum concentration of airborne contaminant to which a person could be exposed for 30 minutes without experiencing escape-impairing symptoms or irreversible health effects.

Liquefied gas

A liquid contained in a compressed-gas cylinder that has a vapor pressure exceeding 276 kPa at 38°C (40 psi at 100°F)

Lower explosive limit (LEL)

The lowest concentration of a substance in air that will produce a flash of fire when an ignition source is present

NFPA

National Fire Protection Association

Oxidizing gas

Gas that initiates or promotes combustion in materials, either by catching fire itself or by causing a fire through the release of oxygen or other gases

Oxygen deficiency

A condition that occurs when a breathable atmosphere contains less than 19.5% oxygen. Note: Normal air contains 20.9% oxygen.

Permissible Exposure Limit (PEL) and Threshold Limit Value (TLV)

Employee airborne exposure limits established for particular chemicals by the Federal Occupational Safety and Health Administration (Fed/OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH), respectively. DOE requires that employee exposures not exceed PELs or TLVs.

Pyrophoric gases

Gases that may spontaneously ignite in air at or below 54°C (130°F). Specific gases may not ignite in all circumstances or may explosively decompose.

RFO

Restricted Flow Orifice

Safety Note

A document used to record engineering calculations or tests on specific equipment. A Safety Note may also specify operational requirements addressed in an Activity Hazard Document (AHD) or in operating instructions. See Pressure Safety and Cryogenics.

STP

Standard temperature and pressure

Time-Weighted Average (TWA), Short-Term Exposure Limit (STEL), and Ceiling (C) standards are summarized as follows:

Organizations and Standards

Work Exposure Duration

Fed/OSHA PEL-TWA and ACGIH TLV-TWA

8-hour shift and 40-hour week

Fed/OSHA PEL-STEL and ACGIH TLV-STEL

15 minutes

Fed/OSHA PEL-C and ACGIH TLV-C

Any point in time

13.7 Required Work Processes

Work Process A. General Requirements
Work Process B. Flammable Gases
Work Process C. Pyrophoric Gases
Work Process D. Health-Hazard Gases
Work Process E. Training

Work Process A. General Requirements

flowchart

  1. Gas Leak Emergencies
    1. Hazardous gas leaks that pose a fire, explosion, or health hazard must be reported to the Fire Department (ext. 7911) after the area has been evacuated.
    2. Ignition sources in the vicinity of leaking flammable gas must be turned off if an immediate hazard does not exist. A leaking hazardous-gas cylinder must not be moved or transported. Room ventilation systems and exhausted enclosures required by this policy must control the hazard until the Fire Department can initiate action. The Fire Department is equipped and trained to contain a leaking gas cylinder in a pressure-rated overpack.
  2. Documentation
    1. Process Safety Documentation. An Activity Hazard Document (AHD) must be developed and approved for all hazardous-gas uses that could cause significant injury or property damage at Berkeley Lab or off-site. (See Safe Work Authorizations for AHD administrative requirements.) Examples of gas uses that typically require AHDs include:
      1. NFPA Classes 3 and 4 Health Hazard gases, and Class 2 gases with poor warning properties (See this chapter’s Work Process D, Health-Hazard Gases)
      2. Flammable gas in quantities greater than 11 m3 (400 cf)
      3. Pyrophoric gases
      4. Gases in situations that may cause oxygen deficiency in a room
    2. Gas Quantity and Location Control
      1. Total quantities of hazardous gases at specific locations must be controlled. Gas quantity limitations (i.e., exempt amounts) are specified in Tables 3D and 3E of the California Building Code. Gas in quantities up to these exempt amounts may be stored, dispensed, handled, or used within each control area or building (i.e., in the absence of defined control areas). Quantities greater than the exempt amounts require building construction modifications. Contact the Fire Department for specific requirements.
      2. To control quantities of hazardous gases at specific locations, a list of hazardous gases must be maintained at each location. This list will itemize gas quantities and identify storage locations. The Berkeley Lab chemical inventory system can help with this task. The list should be included in the AHD, when appropriate. Typical information on the list includes each gas name and hazard category, number of cylinders, cylinder size(s), total cylinder volume(s) at standard temperature and pressure (STP) in cubic meters (m3) and cubic feet (cf), and maximum allowable quantities by hazard category. When incompatibility separations are required, storage locations for each gas must be noted.
  3. Training
    1. Personnel who operate or work on compressed gas and pressure systems must complete the Berkeley Lab Pressure Safety training course(EHS0171). Additional requirements apply to personnel who design or assemble pressure systems. (See Pressure Safety and Cryogenics.)
    2. Personnel who handle or use hazardous gases must complete the Chemical Hygiene and Safety Course (EHS0348). They must also receive specific training on the hazard and safety procedures for each hazardous gas-use operation, including a review of any AHD. This training is the responsibility of the supervisor.
  4. Gas Cylinder Storage and Use Locations
    1. Exits and Lighting. Storage and use of gas cylinders in exit corridors are prohibited. Hazardous gases must be located away from exit routes and doors, unless located in gas cabinets. Adequate natural or artificial lighting must be provided.
    2. Area Signs. Entrances to all areas where hazardous gases are used or stored must be posted with visible and durable gas-hazard-identification signs. Hazardous-gas exterior storage and use areas must have signs that prohibit smoking within 8 m (25 ft).
    3. Exterior Locations. Exterior storage and use areas must be covered with a noncombustible canopy. These areas must be protected from vehicle damage. Cylinders must not be placed on unpaved ground or on surfaces where water can accumulate.
    4. Combustible Materials Separation. Cylinder storage and use locations must be kept clear of all weeds, grass, brush, and trash, as well as any other combustible materials, for a minimum distance of 5 m (15 ft) from all cylinders. Exception: An approved noncombustible barrier, cabinet, or hood may be used instead. (See the Hazardous Materials Separation section, below).
    5. Hazardous Materials Separation. Hazardous gases must be separated from incompatible hazardous materials by distance, barriers, cabinets, or lab hoods, as noted in Table 13.1, below. See Appendix B for hazard categories of specific health hazard gases. When a gas is classified in more than one category, all compatibilities must be considered and the most stringent separation used. Nonhazardous gases (e.g., inerts) may be stored in any hazard category. When gas cylinders must be separated into hazard categories, each category area will be posted with a hazard-category sign.

      Table 13.1 Gas Cylinder Separation by Hazard

      Gas Hazard Category

      Nonflammable

      Corrosive

      Oxidizing

      Flammable

      Pyrophoric

      Toxic

      —a

      6 m (20 ft)b

      6 m (20 ft)b

      6 m (20 ft)b

      Pyrophoric

      6 m (20 ft)b

      6 m (20 ft)b

       

      Flammable

      6 m (20 ft)b

       

       

      Oxidizing

       

       

       

      Corrosive

       

       

       

       

      Footnotes:
      a A dash (—) indicates that cylinders with these hazard ratings may be stored adjacent to each other.
      b Exception 1: Containers of hazardous solids or liquids with a capacity less than 2.3 kg (5 lb) or 1.9 L (0.5 gal) when stored in quantities not exceeding exempt amounts specified in Article 80 of the UFC.
        Exception 2: Distances can be reduced without limit when hazardous materials are: (1) separated by a one-half-hour-rated noncombustible barrier (e.g., 2.5 mm or 12 gauge steel) that extends not less than 50 cm (18 in) above and to the sides of the gas cylinder; or (2) stored in separate approved hazardous materials storage cabinets, gas cabinets, or lab hoods.


    6. Safety Shower and Eyewash. An approved safety shower and eyewash must be maintained within 30 m (100 ft) or 10 seconds (whichever is less) of locations where corrosive, eye-irritating, or skin/eye-toxic gases are stored or used.
  5. Gas Cylinders
    1. Cylinder Transportation
      1. Use only standard DOT cylinders for transporting compressed gas.
      2. Personnel trained to use compressed gases may use standard cylinder carts to transport cylinders within buildings and between adjoining buildings. Carts are preferred, but cylinders weighing 11 kg (25 lb) or less may be hand-carried. Valve-protection caps and plugs must be in place during movement of cylinders. Lecture bottles and other cylinders without protective caps must be transported in standard shipping crates or an equivalent container.

        Go here to watch the Safe Handling of Gas Cylinders video for more detailed information.

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      3. Gas cylinders must be transported between non-adjoining buildings by a person properly trained, licensed, and equipped to transport gas cylinders. Proper transportation is provided by Berkeley Lab Facilities Transportation or by approved Berkeley Lab gas supply subcontractors.
    2. Cylinder Position. Gas cylinders must be stored in a “valve end up” upright position, including conditions where the cylinder is inclined as much as 45 degrees from the vertical. Exceptions include cylinders designed for use in a horizontal position and cylinders with nonliquefied compressed gas that have a water volume less than 5 L (0.18 cf or 1.3 gal).
    3. Cylinder Securing. Gas cylinders must be secured to prevent falling due to accidental contact, vibration, or earthquake. Cylinders must be secured in one of the following ways:
      1. By a noncombustible, two-point restraint system (e.g., chains) that secures the cylinder at the top and bottom one-third portions. Exception: Cylinders less than 1 m (3 ft) tall require only one restraining point.
      2. By a noncombustible rack, framework, cabinet, approved strapping device, secured cylinder cart, or other assembly that prevents the cylinder from falling.
    4. Cylinder Valves, Caps, and Plugs
      1. Gas cylinders designed to have valve-protection caps and valve-outlet caps and plugs must have these devices in place. Exception: when the cylinder is in use, connected for use, or being serviced.
      2. Gas cylinder valves must have a handwheel, spindle key, or other approved control handle on the valve stem while the cylinder is in use. Cylinder valves should be opened slowly. Cylinder valves seat in both the closed and open position and are likely to leak unless left in the fully open or fully closed position.
    5. Unauthorized Cylinder Modification or Use. All labels, markings, and tags provided on the gas cylinder by the manufacturer must be maintained in good condition. Gas cylinder parts must not be modified, tampered with, obstructed, removed, repaired, or painted by the gas user.
    6. Empty Cylinders. Gas cylinders should be left with residual pressure (i.e., typically 200 kPa or 30 psi) to prevent contamination of cylinder contents. Cylinders considered to be empty should be handled with the same precautions as cylinders filled with gas because so-called “empty” cylinders still contain residual gas and pressure. Empty gas cylinders must be labeled “Empty.”
    7. Cylinder Changing. Two people must be present during hazardous-gas purge and cylinder-change procedures. Reconnected gas fittings must be checked for leaks using a leak-detection fluid or other approved method.
    8. Cylinder Temperature Control. Gas cylinders should be stored in the shade and must not be exposed to temperatures exceeding 50°C (125°F).
  6. Gas Flow System
    1. Pressure Safety
      1. Compressed-gas systems must be designed and installed in accordance with the requirements of Chapter 7, Pressure Safety and Cryogenics, except for the following:
        1. Inert-gas systems to 1 MPa gauge (150 psig) with a total stored energy of not more than 100 kJ (75,000 ft-lb)
        2. Compressed-gas cylinder manifolds assembled by the Facilities Department Regulator Shop
        3. Simple flow system with a standard pressure regulator, with pressure-relief devices set to no more than 1 MPa gauge (150 psig) and with no components rated for a working pressure less than 1 MPa gauge
      2. Under no circumstances may any gas be used without a standard pressure regulator that is rated for the service.
      3. Depending on the pressure rating of the system, a Safety Note may be required. Systems must be constructed in accordance with the requirements of Chapter 7, Pressure Safety and Cryogenics.
      4. All pressurized hazardous-gas system connections must be checked for leaks on new gas systems and after reconnection of any fitting.
    2. Pipes and Components
      1. Gas pipes, valves, fittings, regulators, and related components must be constructed of materials compatible with the gases to be contained and must be rated for the service.
      2. In general, gas systems must be constructed of approved metallic tubing with compression fittings, or better. Where nonmetallic tubing is approved, additional controls may be required. Stainless steel components are preferred. Additional requirements apply to systems covered in Chapter 7.
    3. Pipe Labels. Each gas line outside of the source gas cabinet or lab hood that contains compressed gas must be labeled at least every 6 m (20 ft), at every change in direction, at critical shutoff valves, and as needed to provide clear identification. Labels must be durable and display the gas name and direction of gas flow. Exception: Piping that may contain more than one type of gas at various times must have signs or labels posted as needed for clear identification and warning at the manifold, along the piping, and at points of use.
    4. Regulators
      1. Gas system pressure must be reduced through a regulator mounted to the cylinder valve outlet or to a manifold installed by the Regulator Shop. Exception: An excess flow valve may be installed between the cylinder valve and regulator. A regulator of the approved type and design for the specific gas and cylinder combination must be used.
      2. Regulators should be inspected by the Regulator Shop before installation to ensure that the regulator is correct for the particular application and is in safe working condition. Only the Regulator Shop is authorized to alter or repair regulators at Berkeley Lab. Oxygen regulators must be labeled for oxygen service, and used regulators reapplied to oxygen service must be degreased in the Regulator Shop.
    5. Backflow Prevention. Check valves or other backflow-prevention devices must be provided when the backflow of materials could create a hazardous condition.
    6. Shutoff Valves
      1. Required emergency shutoff valves must be easily accessible, the valve location identified by means of a sign, and the valve labeled with the gas name or function. Exception: Gas cylinder valves do not need to be identified.
      2. An emergency gas shutoff valve must be located at the process equipment that uses hazardous gas when this equipment is in a different room than the source gas cylinder.
    7. Accidental Flow Control
      1. Excess flow valves (EFVs) or restrictive flow orifices (RFOs) are recommended and may be required by this policy or EHSS to control accidental gas leaks or flows that could cause a fire, explosion, or health risk.
      2. Highly Toxic and Toxic classified gases procured on Berkeley Lab’s eBuy system from Praxair are delivered with a 0.006 inch RFO. If an experimental system requires greater gas flows than a cylinder with an RFO provides, the RFO may be removed, but only after a hazard analysis has been performed and the EHSS subject matter expert (SME) agrees that the resultant controls will not result in a Toxic gas exposure at the exhaust stack that is greater than the immediately dangerous to life and health (IDLH) level or greater than 50% of the IDLH for Highly Toxic gases. 
      3. When the worst-case catastrophic release of a hazard gas is analyzed and controls evaluated, the catastrophic-gas release rate is calculated using the 5-minute and 30-minute release criteria, depending on whether the gas is nonliquefied or liquefied. 
      4. If local exhaust ventilation is sufficient to keep the exhaust concentration at the stack less than or equal to the IDLH for Toxic gases, or 50% of the IDLH for Highly Toxic gases, an RFO will not be required. However, other engineering controls may be required, depending on the gas system. For example, in semiconductor fabrications, additional controls will be required, including but not limited to gas cabinets with gas panels, excess flow, automatic shutoff valves, toxic gas monitoring systems, etc.
      5. If the worst-case Toxic gas concentration is greater than the IDLH at the stack, or greater than 50% of the IDLH for Highly Toxic gases, calculate the catastrophic release rate using an appropriately sized RFO.
      6. If the resulting Toxic gas concentration at the stack is less than or equal to the IDLH, or 50% of the IDLH for Highly Toxic gases, the combination of ventilation and an RFO satisfies the control requirements. However, depending on the gas system, additional engineering controls may be required.  Contact the Gas SME for additional details.
      7. If the combination of ventilation and an RFO does not satisfy the control requirements and the Toxic gas concentration at the stack exceeds the IDLH, or is greater than 50% of the IDLH for Highly Toxic gases, additional administrative controls are required. For example, while toxic gases are flowing and exhausted via the local exhaust ventilation system, no personnel will be permitted to work on the roof and access will be controlled using a lock and key.
      8. The following decision tree diagrams the graded approach in calculating the worst-case release for Toxic and Highly Toxic gases.

        flowchart
      9. Depending on the pressure rating of the system, a Safety Note may be required. Systems must be constructed in accordance with the requirements of Chapter 7, Pressure Safety and Cryogenics.
  7. Purge Gas. When an inert gas source is used to purge hazardous gas from gas lines that use gases of different hazard categories, a separate purge supply must be used for each category of hazardous gas. It is also preferable to have a separate purge cylinder for each hazardous-gas cylinder in use. Backflow-prevention devices must be installed between the purge gas supply and the hazardous-gas system.
  8. Vacuum Pumps. The type of vacuum-pump oil to be used with gases and chemicals must be analyzed for its compatibility with those gases and chemicals. Hydrocarbon oil should not be used with an oxidizer (i.e., oxygen in concentrations greater than or equal to 25%) or with pyrophoric gases. Inert oils should be used instead. Pumps must have a pressure-relief or shutdown device that prevents the pump from bursting if a line becomes plugged. Oil drip pans should be placed under all pump and oil-filter assemblies.
  9. Ventilation
    1. General Ventilation Requirements
      1. Exhaust ventilation systems for hazardous-gas areas and hazardous-gas uses must be installed in accordance with the California Fire Code and California Mechanical Code and must operate continuously.
      2. General area mechanical ventilation for hazardous gas stored and used indoors must be 0.005 m3/s per square meter (one cfm per square foot) of floor area or greater.
    2. Exhausted Enclosures
      1. General Enclosure Requirements
        1. A gas cabinet or lab hood must be used when exhausted enclosures are required for the storage or use of a hazardous-gas cylinder. Exception: exhausted process equipment enclosures that meet the same general performance criteria as gas cabinets or lab hoods, as approved by the EHSS Industrial Hygiene Group.
        2. Each lab hood or gas cabinet that contains one or more hazardous-gas cylinders must be posted with a sign that identifies the name of the gases and their hazard categories.
        3. Exhausted enclosures for hazardous gases must be constructed of noncombustible materials. Exception: unless approved by the Industrial Hygiene Group based on low gas quantities or concentrations.
      2. Gas Cabinets. Gas cabinets must meet current industry and regulatory specifications, which typically include the following:
        1. Constructed of not less than 12 gauge (2.5 mm or 0.097 in) steel and coated to prevent corrosion
        2. Provided with a self-closing and self-latching cylinder access door
        3. Provided with a noncombustible safety window (6.4 mm or 0.25 in) wire-reinforced safety glass
        4. Provided with self-closing access port(s) or windows of sufficient size that allow hand access to equipment controls
        5. Provided with makeup air inlets that allow air circulation throughout the cabinet when the access port(s) or windows are closed
        6. Provided with an approved fire sprinkler
        7. Provided with exhaust ventilation that ensures:
          1. The cabinet is at negative pressure in relation to the surrounding area
          2. An average velocity of air flow at the face of open access ports or windows of 1 to 1.5 m/s (200 to 300 fpm) with a minimum of 0.75 m/s (150 fpm) at any measurement point
    3. Exhaust Duct Systems and Connections
      1. Exhaust systems must be constructed to current building code, fire code, and ACGIH Industrial Ventilation Manual requirements. For example:
        1. Exhaust ducts for hazardous gases must be constructed of noncombustible materials, constructed of compatible materials (or have interior coatings), and must be sealed and seismically braced.
        2. Exhaust ducts must maintain negative pressure and required flow rates.
      2. The following purge and exhaust systems ancillary to the use of hazardous gas must be connected to the exhaust duct system in an approved manner:
        1. All lines or ducts carrying purged hazardous gas emissions (e.g., pipe vents) or exhausted hazardous gas emissions (e.g., vacuum pump lines)
        2. Exhausted enclosures, gas cabinets, and lab hoods
    4. Ventilation Monitoring
      1. All exhausted enclosures must have a ventilation monitor that measures duct or enclosure exhaust performance and displays a quantitative readout easily visible to the gas user (e.g., magnehelic or better).
      2. When ventilation monitoring is required, the monitor must have local audible and visual alarms that activate when the exhaust flow decreases to 70% to 80% of the required air flow.
  10. Gas Detection
    1. General Detection Requirements
      1. Gas-detection controls must be used when significant toxic, flammable, or oxygen-deficiency leak risks cannot be adequately controlled by other means or when required by codes.
      2. Gas-detection controls must not be used in place of proper primary controls (e.g., approved gas lines) and secondary controls (e.g., ventilation and ventilation monitoring). Ventilation monitoring interlocked with automatic gas shutdown at the gas source may also be required.
      3. Requirements for flammable and health-hazard gas-detection procedures are presented in this chapter’s Work Process B, Flammable Gases, and Work Process D, Health-Hazard Gases. Requirements for oxygen-deficiency detection procedures are presented below. When gas-detection procedures are required, Appendix A is used to determine gas-detector-system maintenance, audit, responsibility, selection, and installation requirements.
    2. Oxygen-Deficiency Detection
      1. Oxygen-deficiency detection controls may be needed to detect a lack of breathable air in a space that could be occupied by someone. This situation may be the result of inadequate ventilation or displacement of air by a gas or process byproduct. Guidelines for oxygen-deficiency detection must be developed on a case-specific and hazard basis through AHD reviews or risk assessments conducted using the Oxygen Deficiency Hazard calculator (See Safe Handling of Cryogenic Liquids, Work Process C, Oxygen-Deficiency Risk Assessment). Oxygen-deficiency detection controls are generally not recommended when engineering controls (e.g., ventilation) can be used to control the hazard.
      2. Work spaces that may be oxygen deficient and have limited personnel access and egress meet the definition of a “confined space” and must meet all the requirements of the Berkeley Lab Confined Spaces program. Portable oxygen detectors, in place of fixed-in-place detectors, are usually sufficient for confined spaces.
  11. Electrical Systems
    1. Electrical equipment and wiring must be installed in accordance with the National Electrical Code. Gas piping and containers must not be designed or placed where they can become part of the electrical circuit or used for grounding.
    2. Required ventilation and control systems must be connected to a standby or emergency source of power to automatically supply electricity in the event of loss of power from the primary source. Exception: when standby power is not available in the building and the gas quantities are below the amounts exempted by the California Fire Code (CFC). Emergency power is required for CFC highly toxic gases in quantities greater than 1 m3 (40 cf).
    3. When standby or emergency power is not provided for hazardous gas facilities, controls, or systems that provide primary control against the development of a hazardous condition, loss of system power will activate automatic gas shutoff. Example: an exhaust duct blower that provides exhaust ventilation for flammable or health-hazard gas process effluents that continue to be generated after power is lost.

Work Process B. Flammable Gases

  1. General. See Work Process A of this chapter for general requirements for all compressed and hazardous (e.g., flammable) gases.
  2. Scope
    1. The requirements of this section apply to the storage and use of compressed and liquefied flammable gas in quantities less than or equal to 11 m3 or 400 cf (e.g., two size 1A hydrogen cylinders containing about 200 cf each) and greater than 0.6 m3 (20 cf).
    2. The Berkeley Lab EHSS Industrial Hygiene Group and the Facilities and Engineering divisions can assist in requirements, designs, and construction for the following gas uses, which are not specifically covered in this section:
      1. Storage and use of flammable gas in quantities greater than 11 m3 (400 cf) for compressed gas and 45 kg (100 lb) for liquefied gas, as specified by the National Fire Protection Association in:
        1. NFPA 50A, Standard for Gaseous Hydrogen Systems at Consumer Sites
        2. NFPA 55,Compressed Gases and Cryogenic Fluids Code
      2. Welding and cutting, as specified by the National Fire Protection Association in:
        1. NFPA 51, Standard for the Design and Installation of Oxygen-Fuel Gas Systems for Welding, Cutting, and Allied Processes
        2. NFPA 51B, Standard for Fire Prevention During Welding, Cutting and Other Hot Work
        3. CFC, Chapter 26 49, Welding and Other Hot Work
      3. Dispensing of compressed liquefied flammable gas
  3. Pipes and Components. Piping and related gas-flow components must be of approved and noncombustible design and construction. Stainless steel pipe and fittings are recommended. Exception: Approved nonmetallic tubing and fittings may be used in lengths up to 1.5 m (5 ft) when flexibility is required, if approved by the EHSS Industrial Hygiene Group.
  4. Gas Cylinder Storage and Use
    1. Interior storage and use rooms must be of noncombustible construction.
    2. Exterior storage and use of cylinders must not be located under a window or within 5 m (20 ft) of smoking, open flames, or other ignition sources. Signs that prohibit smoking within 8 m (25 ft) must be posted. In addition, exterior locations must have a minimum of 25% of the perimeter open to the atmosphere and without walls.
    3. Cylinders of compressed gas in solution and liquefied gas must be stored upright so that the pressure-relief valve is in direct contact with the vapor space of the cylinder.
  5. Ventilation
    1. Negative-pressure local exhaust or positive-pressure dilution ventilation is required at all potential leak points in the gas system where the ventilation rate is less than six air changes per hour. Six air changes per hour is approximately 0.005 m3/s per square meter, or one cfm per square foot, of floor area. The EHSS Industrial Hygiene Group will determine when leak-point ventilation is required.
    2. These leak-point ventilation requirements generally do not apply to process equipment that has undergone adequate product safety evaluation and is specifically designed to handle small quantities of flammable gas.
  6. Gas Detection
    1. Flammable-gas detection procedures may be required for systems that use heavier-than-air gases where there is a significant chance that a flammable-gas leak could be accidentally ignited in air.
    2. The EHSS Industrial Hygiene Group will determine when this third level of hazard control is warranted. When detection procedures for flammable gas are required, consult Appendix A to determine gas-detector system maintenance, audit, responsibility, selection, and installation requirements.

Work Process C. Pyrophoric Gases

  1. General
    1. See Work Process A of this chapter for general requirements for all compressed and hazardous (e.g., pyrophoric) gases.
    2. See this chapter’s Work Process D, Health-Hazard Gases, for information on gas purchase approval, cylinder delivery, cylinder return, and piping and component construction.
    3. Pyrophoric gases include, for example, diborane, phosphine, and silane. Diborane and phosphine are both pyrophoric and CFC Highly Toxic (NFPA Health Hazard Class 4) gases, and therefore require both pyrophoric and toxic (i.e., health hazard) gas safety controls. Silane is an NFPA Health Hazard Class 2 gas, but its primary hazard is its pyrophoricity.
  2. Scope. This section presents general requirements and guidelines for pyrophoric gas use. Additional requirements may apply to the storage and use of pyrophoric gas in quantities greater than 0.3 m3 (10 cf) for gas not in a gas cabinet and 0.6 m3 (20 cf) for gas in a gas cabinet.
  3. Gas Storage and Use
    1. Locations, Barriers, and Cabinets
      1. Whenever possible, silane gas cylinders should be stored and used at exterior locations outside of gas cabinets. Whenever silane is being used outside of a gas cabinet, each silane cylinder must be separated from other hazardous gas cylinders by a 6 mm (0.25 in) thick steel barrier. Silane cylinders stored or used at exterior locations must be located in shelters or bunkers, or provided with a chain-link fence to restrict entry and reduce the impact of an explosion at the location perimeter. Interior storage and use of silane must be in gas cabinets.
      2. Pyrophoric gas that also has an NFPA health-hazard classification of 3 or 4 must be stored in and used in a gas cabinet. Class 3 or 4 health-hazard gas at Berkeley Lab must be stored and used in an interior area because of code restrictions.
      3. Only single-cylinder gas cabinets may be used for pyrophoric gases.
      4. Pyrophoric gas cylinders located in gas cabinets must have mechanical ventilation at a minimum rate of 1 m/s (200 fpm) air velocity across the cylinder valve and gas fittings with the cabinet access port(s) closed.
    2. Gas Flow Controls
      1. Pyrophoric gas systems at any pressure require a Safety Note.
      2. Remote manual shutdown devices for pyrophoric gas flow must be provided outside each gas cabinet or near each gas panel. Dispensing areas must have an emergency shutdown mechanism for all gases that can be operated at a minimum distance of 5 m (15 ft) from the dispensing area.
      3. Pyrophoric gas flow, purge, and exhaust systems must have redundant controls that prevent pyrophoric gas from igniting or exploding in an unsafe and uncontrolled manner. These controls may include excess flow valves, flow orifices, mass flow controller sizing, process bypass line elimination or control, vacuum-pump inert-gas purging, dilution of process effluent with inert gas and ventilation, controlled combustion of process effluent, ventilation monitoring, and automatic gas shutdown.

Work Process D. Health-Hazard Gases

See Work Process A of this chapter for general requirements for all compressed and hazardous (e.g., health-hazard) gases.

  1. Gas Health-Hazard Classification. Health-hazard gases, for the purpose of this chapter, include gases that at lower concentrations may cause significant acute or chronic toxic health effects. These gases can, for example, poison someone and/or cause corrosion, irritation, and disease in human tissue.
    1. Acute Health Hazards. Table 13.2 presents standard CFC and NFPA acute-health-hazard gas classifications and shows each category’s relationship to lethal concentration values. These gas classifications must be used to determine which controls in this section are required for each gas use.
    2. Chronic Health Hazards. In contrast to acute-health-hazard gases, chronic-health-hazard gases can be pure or mixed chemicals under pressure in gas cylinders that have significant longer-term health hazards. Examples include OSHA Select Carcinogens http://www.osha.gov/SLTC/carcinogens/index.html). Gases that are only chronic health hazards will be assigned a health-hazard classification and set of engineering controls by the EHSS Industrial Hygiene Group based on the specific gas and use.

      Table 13.2 Health-Hazard Gas Classifications

      Pure Gas LC50 (ppm)

      Zero to
      200

      Greater than
      200 to 1000

      Greater than
      1000 to 2000

      Greater than
      2000 to 3000

      Greater than
      3000 to 5000

      CFC Toxic Gas Classesa

      Highly Toxicc

      Toxic

      N/A

      NFPA Health Hazard Classesb

      4

      3

      2

      Footnotes:
      a CFC Highly Toxic and Toxic Gases: CFC Highly Toxic gases have a median lethal concentration (one-hour rate LC50) in air of 200 parts per million (ppm) by volume or less of gas. CFC Toxic gases have a LC50 greater than 200 ppm and less than or equal to 2000 ppm.
      b NFPA Class 4, 3, and 2 Health Hazard Gases: NFPA Class 4 gases have a LC50 for acute inhalation toxicity that is less than or equal to 1000 ppm. NFPA Class 3 gases have a LC50 greater than 1000 ppm, but less than or equal to 3000 ppm. NFPA Class 2 gases have a LC50 greater than 3000 ppm, but less than or equal to 5000 ppm.
      c Excimer Gases: Mixtures of Excimer gases might not warrant classification as Highly Toxic. While this system is basically simple in application, any hazard evaluation that is required for precise categorization of this type of material must be performed by experienced, technically competent persons, including but not limited to the EHSD Subject Matter Expert.


    3. Specific Gas Information. See Appendix B for a list of specific health-hazard gases and their corresponding CFC and NFPA classifications. The EHSS Industrial Hygiene Group will assign health-hazard classifications and engineering controls to previously unclassified gases, dilute gases, and gas mixtures.
  2. Small Gas Concentrations and Quantities
    1. The required controls in this health-hazard gases section only apply to concentrations and quantities of gas that are sufficient to cause a gas-leak health hazard. A hazard exists at all potential leak points where a worst-case gas release will result in a small cloud of gas that is at or above the Ceiling Limit or Short-Term Exposure Limit (STEL) (or the Time-Weighted Average [TWA] if no Ceiling Limit or STEL is available).
    2. A leak health hazard exists if the concentration of gas inside the gas source (e.g., cylinder or gas line) is at or above the Ceiling Limit or STEL (or the TWA, if no Ceiling Limit or STEL is available). Exception: when a documented (e.g., in the AHD) gas-release hazard evaluation shows that a leak hazard does not exist. The EHSS Industrial Hygiene Group will approve all leak-hazard evaluations and establish evaluation criteria as needed.
  3. Gas Purchase Approval. Purchase requisitions for NFPA Health Hazard Classes 3 and 4 gases (and Class 2 gases with poor physiological warning properties) and pyrophoric gases must be approved by the EHSS Industrial Hygiene Group. The gas purchase requisition will be sent to the EHSS Industrial Hygiene Group for approval before purchase. Berkeley Lab Procurement will not process the requisition until the EHSS Subject Matter Contact approval is obtained.
  4. Gas Delivery and Return. Facilities Transportation must handle all gases that require prepurchase approval, as follows:
    1. Gases must be kept in exhausted enclosures until they can be delivered directly to the gas user.
    2. Delivery and pickup of gases will be scheduled directly with and handled directly by a person designated by the gas user. The designated person will also sign the Hazardous Shipping Form provided by Facilities Transportation.
    3. Gas cylinder valves will be checked for leaks before delivery and at time of pickup from the gas user.
  5. Gas Flow System. All gas flow systems at any pressure that handle NFPA Health Hazard Classes 2, 3, and 4 gases require a Safety Note and must be designed and constructed in accordance with the requirements of Chapter 7, Pressure Safety and Cryogenics.
  6. Ventilation
    1. Area Ventilation. Area ventilation must be 0.005 m3/s per square meter (one cfm per square foot) of floor area or greater and must be maintained at negative pressure relative to adjacent corridors and nonlaboratory or non-gas-use areas.
    2. General Local Exhaust Requirements
      1. NFPA Classes 3 and 4 gases (and NFPA Class 2 gases with no physiological warning properties): Gas cylinders must be kept in laboratory hoods or gas cabinets.
      2. CFC Highly Toxic and Toxic gases (recommended for other NFPA Class 3 gases): All potential gas leak points must be contained within exhausted enclosures.
      3. NFPA Class 3 gases that are not CFC Toxic gases (and NFPA Class 2 gases with no physiological warning properties): All unapproved components in the gas system must be enclosed and exhausted.
    3. Process Equipment Enclosures. When process equipment enclosures are exhausted, ventilation face velocities at all enclosure holes, cracks, and access ports that may need to be opened in a gas emergency must be 0.5 m/s (100 fpm) or greater. Where emergency access is needed, small (not large) access doors must be used to reduce exhaust requirements.
    4. Purge Vents and Exhaust Lines
      1. All lines or ducts carrying purged or exhausted emissions of health-hazard gases must be connected to an approved exhaust system.
      2. Corrosive gas venting: Significant emissions from corrosive gas venting may require the use of an emissions-control device (e.g., scrubber) to prevent duct corrosion before the purged gas can be vented into the exhaust duct system.
    5. Ventilation Monitoring and Interlocks
      1. CFC Highly Toxic and Toxic Gases. A ventilation monitor with audible and visual alarms is required on the lab hood or gas cabinet where the gas cylinder is kept.
      2. Ventilation monitoring interlocked with automatic gas shutdown may be used in addition to or in place of audible and visual ventilation monitor alarms. In addition, automatic gas shutdown is required based on the gas’s physiological warning properties, as shown in Table 13.3. Ventilation monitoring interlocked with automatic gas shutdown is also recommended for CFC Highly Toxic gases.
  7. Accident Release Evaluation and Control
    1. When required by the EHSS Industrial Hygiene Group, the Activity Hazard Document (AHD) or Safety Note must include an evaluation of the consequences of a worst-case gas release of the largest CFC Highly Toxic or Toxic gas cylinder into the exhaust system. The following release times will be assumed for a worst-case gas release if no flow-control devices are provided: 5 minutes for nonliquefied gases and 30 minutes for liquefied gases. If calculations show that immediately dangerous to life and health (IDLH) concentrations are exceeded at the exhaust stack discharge, restrictive-flow orifices or excess-flow valves should be provided in the cylinder valve or as close to the cylinder valve as possible.
    2. When quantities of CFC Highly Toxic gas exceed 1 m3 (40 cf), gas release controls must be implemented to reduce the exhaust stack discharge concentration to one-half of the IDLH at the point of discharge into the atmosphere.
  8. Gas Detection
    1. The following criteria must be used to determine the need for health-hazard gas detection: gas concentration, quantity, and physiological warning properties. Health-hazard gas detection is only required when the gas posing a health hazard has poor physiological warning properties. Poor warning conditions exist when the concentration and warning properties of the gas are at or above the Ceiling Limit or STEL (or the TWA if no Ceiling Limit or STEL is available) as determined by the EHSS Industrial Hygiene group. See Table 13.3, below, for health-hazard gases that require gas detection, ventilation, and gas-shutdown controls. Exception: If the aggregate quantity of the health-hazard gas in the control area is less than or equal to 1 m3 (40 cf), ventilation monitoring and gas-source shutdown may be used in place of gas detection.
    2. When gas-detection methods are required, use Appendix A to determine gas-detection system maintenance, audit, responsibility, selection, and installation requirements.

Table 13.3 Health-Hazard Gas Controls

REQUIRED CONTROLS

 

Control Area Gas Quantity at STP

 

Any amount

Less than or equal to 1 m3 (40 cf)

Greater than 1 m3 (40 cf)

Physiological Warning Property Rating

Ventilation on Backup Power and Monitored

Ventilation Monitor & Gas Shutdown

Gas Detection and 
Gas Shutdown

Ventilation Monitor and Gas Shutdown (E1)

Gas Detection and Gas Shutdown

(G) Good

Required

(A) Adequate

Required

Recommended

(M) Marginal

Required

Recommended

Recommended

(P) Poor

Required

Recommended

Required

Required (E2)



PHYSIOLOGICAL-WARNING PROPERTY RATINGS
For Select Health-Hazard Gases

1,3-butadiene (G*)

germane (U*)

phosgene (P*)

ammonia (G*)

hydrogen bromide (A*)

phosphine (P*)

arsenic pentafluoride (U*)

hydrogen chloride (A*)

phosphorous pentafluoride (A*)

arsine (P*)

hydrogen cyanide (P*)

phosphorous trichloride (P*)

boron trichloride (A*)

hydrogen fluoride (A*)

phosphorous trifluoride (P*)

boron trifluoride (P*)

hydrogen selenide (P*)

selenium hexafluoride (P)

bromine pentafluoride (P)

hydrogen sulfide (M*)

silane (M*)

bromine trifluoride (P)

iodine pentafluoride (U)

silicon tetrachloride (A*)

carbon monoxide (P*)

methyl bromide (P*)

silicon tetrafluoride (A*)

carbonyl fluoride (U*)

methyl chloride (M)

stibine (P*)

carbonyl sulfide (U)

methyl silane (U)

sulfur dioxide (G*)

chlorine (A*)

nickel carbonyl (P)

sulfur tetrafluoride (P*)

chlorine trifluoride (M*)

nitric oxide (G*)

sulfuryl fluoride (P)

cyanogen (P)

nitrogen dioxide (A*)

tellurium hexafluoride (P)

cyanogen chloride (P)

nitrogen trifluoride (P*)

tungsten hexafluoride (A*)

diborane (P*)

nitrosyl chloride (A)

vinyl chloride (P*)

dichlorosilane (A*)

oxygen difluoride (P)

 

fluorine (M*)

 

 

(A) Adequate: Warning properties are fairly well understood and occur at or below the lowest PEL or TLV. Data uncertainties may exist.
(E1) Exception 1: A ventilation monitor must be installed, but may not need to be interlocked with gas shutdown if procedures for the operation require: (1) an operator to be present at all times while the gas cylinder valve is open, and (2) the gas cylinder valve to be closed if the ventilation alarm is activated. Exceptions must be approved by the EHSS Industrial Hygiene Group.
(E2) Exception 2: If no gas-detection system is available, control measures that provide an equal level of safety must be used.
(G) Good: Warning properties are well understood and occur at or below the lowest PEL or TLV.
(M) Marginal: Warning properties are marginally adequate and are most likely to occur at or below the STEL (or TWA, if no STEL or Ceiling Limit is available). Data uncertainties may exist.
(P) Poor: Warning properties occur at or above the STEL or Ceiling Limit (or TWA, if no STEL or Ceiling Limit is available). Many data uncertainties may exist. Gas may have high-hazard toxicity properties.
(U) Undetermined: Information on warning properties is lacking. EHSS will evaluate on a case-by-case basis.
(*) Available gas-detection system(s) have been identified.
(—) No general requirement.
_____________________

Work Process E. Training

Role

Requirement

Compressed Gas System Operators and Technicians

EHS0171, Pressure Safety

Hazardous Gas System Operator

EHS0348, Chemical Hygiene and Safety


Document Number

PUB-3000 Reference

Title

Type

07.07.015.001

Chapter 13

Gases

Program

 

Chapter 1

General Policy and Responsibilities

Program

 

Chapter 4

Industrial Hygiene

Program

 

Chapter 7

Pressure Safety and Cryogenics

Program

 

Chapter 12

Fire Prevention and Protection

Program

 

Chapter 24

EH&S Training

Program

13.8 Source Requirements

13.9 Reference Documents

Document Number

PUB-3000 Reference

Title

Type

07.01.002.000

Chapter 1

General Policy and Responsibilities

Program

 

Chapter 4

Industrial Hygiene

Program

07.07.026.000

Chapter 7

Pressure Safety and Cryogenics

Program

07.11.001.000

Chapter 12

Fire Prevention and Protection

Program

07.07.015.001

Chapter 13

Gases

Program

07.04.001.000

Chapter 24

EH&S Training

Program

Other References

13.10 Appendices

Appendix A. Gas-Detection System Requirements

This appendix contains requirements for maintenance, selection, and installation of gas-detection systems. Explanations for when gas detection is required are presented in Work Process A, General Requirements; Work Process B, Flammable Gases; and Work Process D, Health-Hazard Gases, of this chapter.

  1. Detection System Maintenance
    1. General Maintenance Requirements
      1. The principal investigator or gas-use supervisor is primarily responsible for the management of gas-detection system maintenance related to his or her project or operation.
      2. Maintenance must at a minimum follow manufacturer’s recommendations, including frequency of maintenance. Testing of the detection system’s ability to detect and transmit a signal to the Fire Department must follow NFPA guidelines, or must occur on at least a quarterly basis. The Facilities Department will provide technical guidance, if requested.
    2. Maintenance Personnel
      1. The principal investigator may assign maintenance tasks to qualified subordinates, the Facilities Department, or contractors.
      2. Personnel conducting detector maintenance must be adequately trained, having detector manufacturer recommended training, or an equivalent, and be certified as “qualified” maintenance personnel.
    3. Maintenance Documentation
      1. A formal system of documentation will be maintained for each gas-detection system, and will include:
        1. Manufacturer’s operation and service manuals
        2. Preventive maintenance procedures, post-maintenance testing, schedules, and records of results
        3. Procedures and records for verifying proper connection of detector alarms and interlocks
        4. Records of all repairs, calibrations, nonroutine maintenance, and system failures
        5. Names and qualifications of maintenance personnel
        6. Calibration source documentation
      2. A one-year summary (e.g., log) of function checks and maintenance actions performed must be visibly maintained on the detector system. Minimum summary information must include the date, person’s name, and action taken.
  2. Detection System Selection
    1. Listing. Systems must be listed by Underwriters Laboratory, Factory Mutual, or Canadian Safety Association, and the California State Fire Marshall’s office, or equivalent. The Fire Department may approve unlisted equipment if listed equipment is not available or is inferior.
    2. Performance. Gas-detector sensitivity must be below the lowest Permissible Exposure Limit (PEL) or Threshold Limit Value (TLV) for health hazard gases and/or at or below 10–15% of the Lower Explosive Limit (LEL) level for flammable gases.
    3. Hardware. System hardware must include:
      1. Separate relays for “warning” (low-concentration gas detection), “alarm” (high-concentration gas detection), and “trouble” (malfunction) conditions, and normally open and normally closed dry-contact-relay output capability for specified but adjustable levels of gas detection
      2. Capability system that is installed as fixed-in-place, with hard-wired and plumbed connections
      3. Control protection from direct unauthorized personnel access
  3. Detection System Installations
    1. Design. Detection system installations will be designed and documented (i.e., plans and as-built drawings) by the Facilities Department. A Facilities Department licensed professional engineer and EHSS Fire Protection Engineer will approve all designs prior to contract award or installation. In addition, an EHSS Industrial Hygienist will approve all toxic and oxygen-deficiency-detection system designs.
    2. Sample Point Locations. Gas-detector sample points must be placed immediately adjacent to potential leak points or in the flow path of exhausted enclosures.
    3. Alarm Locations. All gas-detection systems must have:
      1. Audible and visual alarms in the following locations: gas-supply location, gas-use or operator room, and outside the gas-use room (e.g., corridor).
      2. An alarm status and gas-concentration readout panel must be located outside the gas-use room.
      3. Local audible and visual alarms must be specific and distinct from fire alarm bells and have signs to indicate the alarm’s meaning and required personnel action.
    4. Alarm Monitoring. Gas-detection systems required by this policy must have alarm connections to the Berkeley Lab Fire Department Alarm Room, which continuously monitors alarm status. Alarm connections must be made through the building and Berkeley Lab fire alarm system, must transmit “alarm” and “trouble” signals as separate tones, and must be made in accordance with NFPA 72.
    5. Alarm Conditions and Actions.
      1. Alarm conditions must consist of “trouble,” “warning,” and “alarm.”
      2. Toxic-gas “warning” and “alarm” level setpoints must normally be set at less-than-PEL/TLV and equal-to-PEL/TLV concentrations, respectively.
      3. Flammable-gas warning and alarm level setpoints must normally be set at 10–15% LEL and 20% LEL, respectively.
      4. Low-level “warnings” must activate local alarms and personnel response only.
      5. High-level “alarms” must activate local-area evacuation, automatic gas shutdown at the gas source, and Fire Department notification.
    6. Power and Control
      1. The detection and alarm systems will be connected to emergency power. In the event of a power failure, the detection system must continue to operate without interruption (e.g., must have an uninterruptable power supply), or gas systems must be automatically shut down at the gas source.
      2. Power connections, control switches, and adjustments that affect the system’s safety control must be protected from direct access (e.g., must be hard-wired or covered and locked).

Appendix B. Specific Health-Hazard Gas Classifications



Gas Name (Symbol)

NFPA Health Class



UFC Hazard Classes

ammonia (NH3)

3

C, F(LG)

arsenic pentafluoride (AsF5)

4

T(H), C, CAR, WR(1)

arsine (AsH3)

4

T(H), F, F(LG)

benzene in air

CAR, F @1.4%, Liquid

boron trichloride (BCl3)

3

T, C, WR(1)

boron trifluoride (BF3)

3

T, C, WR(1)

bromine pentafluoride

3

T, C, WR(3), O(3)

bromine trifluoride (BrF3)

4

T(H), C, WR(3), O

1,3-butadiene (C4H6)

4

F, CAR, UR(2), I

carbon monoxide (CO)

2

F(G)

carbonyl fluoride (COF2)

3

T, I, WR(1)

carbonyl sulfide

3

T, C, F(LG), OHH

chlorine (Cl2)

3

T, C, O(LG)

chlorine trifluoride (ClF3)

4

T(H),C,O(LG),UR(3D),WR(2)

cyanogen (C2N2)

4

T(H), C, F(G)

cyanogen chloride (ClCN)

4

T(H), I, UR(2), WR(1)

diborane (H6B2)

4

T(H), P, I, UR(3D), WR(1)

dichlorosilane (SiH2Cl2)

3

C, F(LG), WR(1)

fluorine (F2)

4

T(H), C, WR(2), O(G)

germanium tetrahydride (GeH4)

4

T(H), I, F(G), UR(3D)

hydrogen bromide (HBr)

2

I

hydrogen chloride (HCl)

3

C

hydrogen cyanide (HCN)

4

T(H), F(LG), UR(2), WR(1)

hydrogen fluoride (HF)

3

T, C, WR(2)

hydrogen selenide (H2Se)

4

T(H), F(LG), I

hydrogen sulfide (H2S)

3

T, I, F(LG)

iodine pentafluoride (IP5)

NL

 

methyl bromide (CH3Br)

3

T, C, F(LG)

methyl chloride (CH3Cl)

2

F(LG), WR(1), I

methyl silane

3

 

nickel carbonyl Ni(CO)4

4

T(H),I,F,UR(3D),WR(1), Liquid

nitric oxide (NO)

3

T, I, O(LG)

nitrogen dioxide (NO2)

4

T(H), C, O(LG), WR(1)

nitrogen trifluoride (NF3)

3

I, O(G), OHH

nitrosyl chloride (NOCl)

NL

 

oxygen difluoride (OF2)

NL

 

phosgene (COCl2)

4

T, I, WR(1)

phosphine (PH3)

4

T(H), P

phosphorous pentafluoride (PF5)

3

T, C, WR(1), WR(1)

phosphorous trichloride (PCl3)

3

T, P, C, UR(2), WR(2), Liquid

phosphorous trifluoride (PF3)

3

T, I, WR(1)

selenium hexafluoride

NL

 

silane (silicontetrahydride-SiH4)

2

P, UR(1)

silicon tetrachloride (SiCl4)

3

C, WR(1), Liquid

silicon tetrafluoride (SiF4)

3

T

stibine (SbH3)

4

T(H), F(G)

sulfur dioxide (SO2)

2

I

sulfur tetrafluoride (SF4)

4

T(H), C, UR(2), WR(1)

sulfuryl fluoride (SO2F2)

3

T, I

tellurium hexafluoride (TeF6)

NL

 

tungsten hexafluoride (WF6)

3

T, C, WR(2)

vinyl chloride (C2H3Cl)

4

T, I, F(LG), UR(1), CAR

Abbreviations:
CAR — Carcinogen
C — Corrosive
F — Flammable: Gas (G), Liquefied Gas (LG)
I — Irritant
NL — Not Listed
O — Oxidizer: Gas (G); Liquefied Gas (LG); Classes (1), (2), (3), and (4)
OHH — Other Health Hazard
T — Toxic: Highly (H)
UR — Unstable Reactive: Classes (1), (2), (3), Detonatable (3D), and (4)
WR — Water Reactive: Classes (1), (2), (3), and (4)

 

    

_____________________

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