Chlorine is a “toxic gas” and as such it has special requirements in the IFC as well as the IMC. I have written about how we design our gas cabinets, gas rooms, enclosures, and storage areas based on the IFC Chapter 50 and 60 requirements. In this article, I will address the IMC requirements which are referenced in the IFC. I will be using the 2015 IMC for my references…
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502.8 Hazardous materials—general requirements Exhaust ventilation systems for structures containing hazardous materials shall be provided as required in Sections 502.8.1 through 502.8.5. 502.8.1 Storage in EXCESS OF THE MAXIMUM ALLOWABLE QUANTITIES Indoor storage areas and storage buildings for hazardous materials in amounts exceeding the maximum allowable quantity per control area shall be provided with mechanical exhaust ventilation or natural ventilation where natural ventilation can be shown to be acceptable for the materials as stored. 502.8.1.1 System requirements. Exhaust ventilation systems shall comply with all of the following:
502.8.2 Gas rooms, exhausted enclosures, and gas cabinets The ventilation system for gas rooms, exhausted enclosures, and gas cabinets for ANY QUANTITY of hazardous material shall be designed to operate at a negative pressure in relation to the surrounding area. Highly toxic and TOXIC GASES shall comply with Sections 502.9.7.1, 502.9.7.2, and 502.9.8.4. |
The room or enclosure containing the hazardous materials MUST BE DESIGNED TO OPERATE AT A NEGATIVE PRESSURE to prevent the vapors from escaping into other areas in the event of a leak. Below are Sections 502.9.7.1, 502.9.7.2, and 502.9.8.4,
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502.9.7 Highly toxic and toxic compressed gases—ANY QUANTITY Ventilation exhaust shall be provided for highly toxic and toxic compressed gases in ANY QUANTITY as required by Sections 502.9.7.1 and 502.9.7.2 502.9.7.1 Gas cabinets Gas cabinets containing highly toxic or toxic compressed gases in any quantity shall comply with Section 502.8.2 and the following requirements: 1. The average ventilation velocity at the face of gas cabinet access ports or windows shall be not less than 200 feet per minute (1.02 m/s) with a minimum velocity of 150 feet per minute (0.76 m/s) at any point at the access port or window. 2. Gas cabinets shall be connected to an exhaust system. 3. Gas cabinets shall not be used as the sole means of exhaust for any room or area. 502.9.7.2 Exhausted enclosures Exhausted enclosures containing highly toxic or toxic compressed gases in ANY QUANTITY shall comply with Section 502.8.2 and the following requirements: 1. The average ventilation velocity at the face of the enclosure shall be not less than 200 feet per minute (1.02 m/s) with a minimum velocity of 150 feet per minute (0.76 m/s). 2. Exhausted enclosures shall be connected to an exhaust system. 3. Exhausted enclosures shall not be used as the sole means of exhaust for any room or area. |
A gas cabinet used to contain Cl2 must comply with BOTH the general requirements found in Chapter 50 of the IFC and the specific requirements found in this section of the IMC. Chapter 50 of the IFC provides the basic construction requirements and states that the cabinet must be maintained at a negative pressure relative to the surrounding environment.
Because of the hazards presented by CL2, this section includes additional requirements that are the same ventilation exhaust requirements found in Section 6004.1.2 of the IFC. These include specific velocity minimums for ventilation at the face of the cabinets, a connection to an exhaust system, and prohibition of the use of gas cabinets as the sole method of ventilation in a room or area of a building.
Additionally, Section 6004.1.2 of the IFC requires that gas cabinets containing toxic and highly toxic gases specifically be protected with an automatic sprinkler system complying with NFPA 13. Other types of extinguishing systems are prohibited.
An exhausted enclosure used to contain Cl2 must comply with BOTH the general requirements found in Chapter 50 of the IFC and the specific requirements found in this section. Chapter 50 of the IFC contains the basic construction requirements, requires that the exhausted enclosure beat a negative pressure relative to the surrounding environment, AND requires an approved automatic extinguishing system.
Because of the hazards presented by toxic and highly toxic gases, this section includes additional requirements that are the same ventilation exhaust requirements found in Section 6004.1.3 of the IFC. These include:
- specific velocity minimums for ventilation at the face of the enclosure,
- a connection to an exhaust system, and
- restrictions on the use of exhausted enclosures as the sole method of ventilation in a room or any area of a building
Additionally, Section 6004.1.3 of the IFC requires that exhausted enclosures be protected with an automatic sprinkler system complying with NFPA 13. Other types of extinguishing systems are PROHIBITED.
The following are the ventilation requirements for areas where Cl2 gas exceeds the MAQ, which is 810 cubic ft or 1,620 cubic ft if gas cabinets or exhausted enclosures are used. More specifically, these provisions focus on both stationary and portable containers and require that the exhaust collected from these areas, whether through gas cabinets, exhausted enclosures, gas rooms, or local exhaust system, be directed to a treatment system to avoid the release of harmful amounts of Cl2 gas to the atmosphere. The IFC does allow, under certain conditions, the use of containment vessels or containment systems instead of the use of gas cabinets and exhausted enclosures.
Cl2 rooms or spaces containing gas cabinets and exhausted enclosures must be connected to an exhaust system. Although gas cabinets and exhausted enclosures provide a mechanism to exhaust hazardous gases, they are NOT allowed to be the only method of exhaust for the room or area of the building in which they are located. The ventilation for the room or area should be in accordance with Section 502.8, Hazardous materials—general requirements.
Section 502.9.8.5 requires that gas cabinets and exhausted enclosures be directed through a treatment system when mandated by the IFC.
The code also requires {tip title=”Portable Tank Definition” content=”A packaging of more than 60-gallon (227 L) capacity and designed primarily to be loaded into or on or temporarily attached to a transport vehicle or ship and equipped with skids, mountings or accessories to facilitate handling of the tank by mechanical means. It does not include any cylinder having less than a 1,000-pound (454 kg) water capacity, cargo tank, tank car tank or trailers carrying cylinders of more than 1,000-pound (454 kg) water capacity.”}portable tanks{/tip} have some means available to collect gases that escape through either a valve or a fitting.
These gases must be collected through either ducts or some type of collection system. Because these tanks are portable, they may require a system in which the point of collection is flexible to address the different types and configurations of tanks being used. The local exhaust system used to collect these gases must be located in a gas room connected to a treatment system. This section applies to both indoor and outdoor situations.
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502.9.8 Highly toxic and toxic compressed gases — QUANTITIES EXCEEDING THE MAQ PER CONTROL AREA Ventilation exhaust shall be provided for highly toxic and toxic compressed gases in amounts exceeding the maximum allowable quantities per control area as required by Sections 502.9.8.1 through 502.9.8.6. 502.9.8.1 Ventilated areas The room or area in which indoor 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.
502.9.8.2 Local exhaust for {tip title=”Portable Tank Definition” content=”A packaging of more than 60-gallon (227 L) capacity and designed primarily to be loaded into or on or temporarily attached to a transport vehicle or ship and equipped with skids, mountings or accessories to facilitate handling of the tank by mechanical means. It does not include any cylinder having less than a 1,000-pound (454 kg) water capacity, cargo tank, tank car tank or trailers carrying cylinders of more than 1,000-pound (454 kg) water capacity”}portable tanks{/tip} A means of local exhaust shall be provided to CAPTURE LEAKAGE from indoor and outdoor 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 where required by the International Fire Code.
502.9.8.3 Piping and controls — {tip title=”Stationary Tank Definition” content=”Packaging designed primarily for stationary installations not intended for loading, unloading or attachment to a transport vehicle as part of its normal operation in the process of use. It does not include cylinders having less than a 1,000-pound (454 kg) water capacity.”}stationary tanks{/tip} FILLING OR DISPENSING CONNECTIONS on indoor stationary tanks 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 where required by the International Fire Code.
502.9.8.4 {tip title=”Gas Room Definition” content=”A separately ventilated, fully enclosed room in which only compressed gases and associated equipment and supplies are stored or used.”}Gas rooms{/tip} The ventilation system for GAS ROOMS SHALL BE DESIGNED TO OPERATE AT A NEGATIVE PRESSURE in relation to the surrounding area. The exhaust ventilation from gas rooms shall be directed to an exhaust system.
502.9.8.5 Treatment system The exhaust ventilation from gas cabinets, exhausted enclosures, and gas rooms, and local exhaust systems required in Sections 502.9.8.2 and 502.9.8.3 shall be directed to a TREATMENT SYSTEM where required by the International Fire Code.
502.9.8.6 Process equipment Effluent from indoor and outdoor process equipment containing highly toxic or toxic compressed gases which could be discharged to the atmosphere shall be processed through an EXHAUST SCRUBBER or other processing system. Such systems shall be in accordance with the International Fire Code. |
When Cl2 gases are stored in gas cabinets, exhausted enclosures, and gas rooms, the exhaust is NOT TO BE RELEASED DIRECTLY TO THE ATMOSPHERE. Instead, ALL exhaust MUST go through a treatment system that complies with the IMC and IFC Sections 6004.2.2.7.1 through 6004.2.2.7.5.
There are two (2) exceptions to the requirements for treatment systems in the IFC that are related to Cl2 gas in storage when several specific controls have been installed. These controls include:
- redundancy with the use of caps or plugs on valve outlets;
- handwheel-operated valves to prevent movement and
- the use of containment vessels or containment systems in accordance with the IFC.
Exception 2 is specific to toxic gases in use where a gas detection system is installed that has a sensing interval NOT EXCEEDING 5 minutes and an approved fail-safe automatic-closing valve located next to the cylinder valves. The fail-safe valve is to CLOSE when gas is detected at or above the PEL.
The rest of the IFC requirements provide guidance on the intended treatment of the gases, which could be through dilution, absorption, containment, neutralization,
burning, or any other method as long as the largest single vessel is accounted for. Generally, the criterion is to reduce the gas to one-half of the immediate dangerous-to-life-and-health (IDLH) level. The IFC further discusses the sizing of the system based on the rate of release and whether the container is stationary or portable.