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The indoor storage and use of highly toxic or toxic compressed gases shall be in accordance with Sections 6004.2.1 through 6004.2.2.10.3.
6004.2.1 Applicability
The applicability of regulations governing the indoor storage and use of highly toxic and toxic compressed gases shall be as set forth in Sections 6004.2.1.1 through 6004.2.1.3.
6004.2.1.1 Quantities Not Exceeding the Maximum Allowable Quantity Per Control Area
The indoor storage or use of highly toxic and toxic gases in amounts not exceeding the maximum allowable quantity per control area set forth in Table 5003.1.1(2) shall be in accordance with Sections 5001, 5003, 6001 and 6004.1.
6004.2.1.2 Quantities Exceeding the Maximum Allowable Quantity Per Control Area
The indoor storage or use of highly toxic and toxic gases in amounts exceeding the maximum allowable quantity per control area set forth in Table 5003.1.1(2) shall be in accordance with Sections 6001, 6004.1, 6004.2 and Chapter 50.
6004.2.1.3 Ozone Gas Generators
The indoor use of ozone gas-generating equipment shall be in accordance with Section 6005.
6004.2.2 General Indoor Requirements
The general requirements applicable to the indoor storage and use of highly toxic and toxic compressed gases shall be in accordance with Sections 6004.2.2.1 through 6004.2.2.10.3.
6004.2.2.1 Cylinder and Tank Location
Cylinders shall be located within gas cabinets, exhausted enclosures or gas rooms. Portable and stationary tanks shall be located within gas rooms or exhausted enclosures.
6004.2.2.2 Ventilated Areas
The room or area in which gas cabinets or exhausted enclosures are located shall be provided with exhaust ventilation. Gas cabinets or exhausted enclosures shall not be used as the sole means of exhaust for any room or area.
6004.2.2.3 Leaking Cylinders and Tanks
One or more gas cabinets or exhausted enclosures shall be provided to handle leaking cylinders, containers or tanks.
Exceptions:
  1. Where cylinders, containers or tanks are located within gas cabinets or exhausted enclosures.
  2. Where approved containment vessels or containment systems are provided in accordance with all of the following:
    1. Containment vessels or containment systems shall be capable of fully containing or terminating a release.
    2. Trained personnel shall be available at an approved location.
    3. Containment vessels or containment systems shall be capable of being transported to the leaking cylinder, container or tank.
6004.2.2.3.1 Location
Gas cabinets and exhausted enclosures shall be located in gas rooms and connected to an exhaust system.
6004.2.2.4 Local Exhaust for Portable Tanks
A means of local exhaust shall be provided to capture leaks from portable tanks. The local exhaust shall consist of portable ducts or collection systems designed to be applied to the site of a leak in a valve or fitting on the tank. The local exhaust system shall be located in a gas room. Exhaust shall be directed to a treatment system in accordance with Section 6004.2.2.7.
6004.2.2.5 Piping and Controls—Stationary Tanks
In addition to the requirements of Section 5003.2.2, piping and controls on stationary tanks shall comply with the following requirements:
  1. Pressure relief devices shall be vented to a treatment system designed in accordance with Section 6004.2.2.7.
    Exception: Pressure relief devices on outdoor tanks provided exclusively for relieving pressure due to fire exposure are not required to be vented to a treatment system provided that:
    1. The material in the tank is not flammable.
    2. The tank is not located in a diked area with other tanks containing combustible materials.
    3. The tank is located not less than 30 feet (9144 mm) from combustible materials or structures or is shielded by a fire barrier complying with Section 6004.3.2.1.1.
  2. Filling or dispensing connections shall be provided with a means of local exhaust. Such exhaust shall be designed to capture fumes and vapors. The exhaust shall be directed to a treatment system in accordance with Section 6004.2.2.7.
  3. Stationary tanks shall be provided with a means of excess flow control on all tank inlet or outlet connections.
    Exceptions:
    1. Inlet connections designed to prevent backflow.
    2. Pressure relief devices.
6004.2.2.6 Gas Rooms
Gas rooms shall comply with Section 5003.8.4 and both of the following requirements:
  1. The exhaust ventilation from gas rooms shall be directed to an exhaust system.
  2. Gas rooms shall be equipped with an approved automatic sprinkler system. Alternative fire-extinguishing systems shall not be used.
6004.2.2.7 Treatment Systems
The exhaust ventilation from gas cabinets, exhausted enclosures and gas rooms, and local exhaust systems required in Sections 6004.2.2.4 and 6004.2.2.5 shall be directed to a treatment system. The treatment system shall be utilized to handle the accidental release of gas and to process exhaust ventilation. The treatment system shall be designed in accordance with Sections 6004.2.2.7.1 through 6004.2.2.7.5 and Section 510 of the International Mechanical Code.
Exceptions:
  1. Highly toxic and toxic gases—storage. A treatment system is not required for cylinders, containers and tanks in storage where all of the following controls are provided:
    1. Valve outlets are equipped with gastight outlet plugs or caps.
    2. Handwheel-operated valves have handles secured to prevent movement.
    3. Approved containment vessels or containment systems are provided in accordance with Section 6004.2.2.3.
  2. Toxic gases—use. Treatment systems are not required for toxic gases supplied by cylinders or portable tanks not exceeding 1,700 pounds (772 kg) water capacity where a gas detection system complying with Section 6004.2.2.10 and listed or approved automatic-closing fail-safe valves are provided. The gas detection system shall have a sensing interval not exceeding 5 minutes. Automatic-closing fail-safe valves shall be located immediately adjacent to cylinder valves and shall close when gas is detected at the permissible exposure limit (PEL) by a gas sensor monitoring the exhaust system at the point of discharge from the gas cabinet, exhausted enclosure, ventilated enclosure or gas room.
6004.2.2.7.1 Design
Treatment systems shall be capable of diluting, adsorbing, absorbing, containing, neutralizing, burning or otherwise processing the contents of the largest single vessel of compressed gas. Where a total containment system is used, the system shall be designed to handle the maximum anticipated pressure of release to the system when it reaches equilibrium.
6004.2.2.7.2 Performance
Treatment systems shall be designed to reduce the maximum allowable discharge concentrations of the gas to one-half immediate by dangerous to life and health (IDLH) at the point of discharge to the atmosphere. Where more than one gas is emitted to the treatment system, the treatment system shall be designed to handle the worst-case release based on the release rate, the quantity and the IDLH for all compressed gases stored or used.
6004.2.2.7.3 Sizing
Treatment systems shall be sized to process the maximum worst-case release of gas based on the maximum flow rate of release from the largest vessel utilized. The entire contents of the largest compressed gas vessel shall be considered.
6004.2.2.7.4 Stationary Tanks
Stationary tanks shall be labeled with the maximum rate of release for the compressed gas contained based on valves or fittings that are inserted directly into the tank. Where multiple valves or fittings are provided, the maximum flow rate of release for valves or fittings with the highest flow rate shall be indicated. Where liquefied compressed gases are in contact with valves or fittings, the liquid flow rate shall be utilized for computation purposes. Flow rates indicated on the label shall be converted to cubic feet per minute (cfm/min) (m3/s) of gas at normal temperature and pressure (NTP).
6004.2.2.7.5 Portable Tanks and Cylinders
The maximum flow rate of release for portable tanks and cylinders shall be calculated based on the total release from the cylinder or tank within the time specified in Table 6004.2.2.7.5. Where portable tanks or cylinders are equipped with approved excess flow or reduced flow valves, the worst-case release shall be determined by the maximum achievable flow from the valve as determined by the valve manufacturer or compressed gas supplier. Reduced flow and excess flow valves shall be permanently marked by the valve manufacturer to indicate the maximum design flow rate. Such markings shall indicate the flow rate for air under normal temperature and pressure (NTP).
TABLE 6004.2.2.7.5
RATE OF RELEASE FOR CYLINDERS AND PORTABLE TANKS
VESSEL TYPE NONLIQUEFIED (minutes) LIQUEFIED (minutes)
Containers 5 30
Portable tanks 40 240
6004.2.2.8 Emergency Power
Emergency power shall be provided for the following systems in accordance with Section 603:
  1. Exhaust ventilation system.
  2. Treatment system.
  3. Gas detection system.
  4. Smoke detection system.
  5. Temperature control system.
  6. Fire alarm system.
  7. Emergency alarm system.
6004.2.2.8.1 Fail-Safe Engineered Systems
Emergency power shall not be required for mechanical exhaust ventilation, treatment systems and temperature control systems where approved fail-safe engineered systems are installed.
6004.2.2.9 Automatic Fire Detection System—Highly Toxic Compressed Gases
An approved automatic fire detection system shall be installed in rooms or areas where highly toxic compressed gases are stored or used. Activation of the detection system shall sound a local alarm. The fire detection system shall comply with Section 907.
6004.2.2.10 Gas Detection System
A gas detection system complying with Section 916 shall be provided to detect the presence of gas at or below the PEL or ceiling limit of the gas for which detection is provided. The system shall be capable of monitoring the discharge from the treatment system at or below one-half the IDLH limit and shall initiate a response in accordance with Sections 6004.2.2.10.1 through 6004.2.2.10.3 if the gas detection alarm is activated.
Exception: A gas detection system is not required for toxic gases when the physiological warning threshold level for the gas is at a level below the accepted PEL for the gas.
6004.2.2.10.1 Alarms
The gas detection system shall initiate a local alarm and transmit a signal to a constantly attended control station when a short-term hazard condition is detected. The alarm shall be both audible and visible and shall provide warning both inside and outside the area where gas is detected. The audible alarm shall be distinct from all other alarms.
Exception: Signal transmission to a constantly attended control station is not required where not more than one cylinder of highly toxic or toxic gas is stored.
6004.2.2.10.2 Shut Off of Gas Supply
The gas-detection system shall automatically close the shutoff valve at the source on gas supply piping and tubing related to the system being monitored for whichever gas is detected.
Exception: Automatic shutdown is not required for reactors utilized for the production of highly toxic or toxic compressed gases where such reactors are:
  1. Operated at pressures less than 15 pounds per square inch gauge (psig) (103.4 kPa).
  2. Constantly attended.
  3. Provided with emergency shutoff valves that have ready access.
6004.2.2.10.3 Valve Closure
Automatic closure of shutoff valves shall be in accordance with the following:
  1. Where the gas-detection sampling point initiating the gas detection system alarm is within a gas cabinet or exhausted enclosure, the shutoff valve in the gas cabinet or exhausted enclosure for the specific gas detected shall automatically close.
  2. Where the gas-detection sampling point initiating the gas detection system alarm is within a gas room and compressed gas containers are not in gas cabinets or exhausted enclosures, the shutoff valves on all gas lines for the specific gas detected shall automatically close.
  3. Where the gas-detection sampling point initiating the gas detection system alarm is within a piping distribution manifold enclosure, the shutoff valve for the compressed container of specific gas detected supplying the manifold shall automatically close.
Exception: Where the gas-detection sampling point initiating the gas-detection system alarm is at a use location or within a gas valve enclosure of a branch line downstream of a piping distribution manifold, the shutoff valve in the gas valve enclosure for the branch line located in the piping distribution manifold enclosure shall automatically close.

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