1.3 Approved containment vessels or containment systems are provided in

accordance with Section 6004.2.2.3. 2. Highly toxic and toxic gases—use. Treatment systems are not required for highly toxic and toxic gases supplied by stationary tanks, portable tanks, or cylinders where a gas detection system complying with Section 6004.4.8 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.

6004.4.5.1 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.

6004.4.5.2 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.

6004.4.5.3 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.

6004.4.5.4 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) (m 3/s) of gas at normal temperature and pressure (NTP).

6004.4.5.5 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.

6004.4.6 Emergency power. Emergency power shall be provided for the following
systems in accordance with Section 604:

1. Exhaust ventilation system.
2. Treatment system.
3. Gas detection system.
4. Smoke detection system.

6004.4.6.1 Fail-safe systems. Emergency power shall not be required for mechanical
exhaust ventilation and treatment systems where approved fail-safe systems are installed
and designed to stop gas flow.

6004.4.7 Automatic fire detection system. An approved automatic fire detection system
shall be installed in rooms or areas where highly toxic and 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.

6004.4.8 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.

Exceptions:
1. 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.
2. A gas detection system is not required for highly toxic and toxic gases where
cylinders, portable tanks, and all non-continuously welded connects are within a gas
cabinet or exhausted enclosures.

6004.4.8.1 Alarms. The gas detection system shall initiate a local alarm and transmit a
signal to an approved location.

6004.4.8.2 Shut off of gas supply. The gas detection system shall automatically close the
shut off 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 highly toxic and toxic compressed gas
systems where all the following controls are provided:
1. Constantly attended/supervised.
2. Provided with emergency shutoff valves that have ready access.

(Ord. 3018-13 § 2; Ord. 3101-16 § 1; Ord. 3148-19 § 1; Ord. 3247-25, 10/21/2025)