Anhydrous Ammonia is NOT a toxic nor highly toxic gas, as defined by the International Fire Code (IFC). But if it is not managed as a “toxic,” how do we manage our ammonia gas?
The IFC actually puts Anhydrous Ammonia in the…
CORROSIVE category.
The code makes mention of NH3’s flammable range, but by definition, it is NOT a flammable gas.
So what does it means when we have a CORROSIVE GAS and what are our requirements per the IFC?
NOTE: links are to FREE access to the code provided by ICC
Chapter 50: Hazardous Materials—General Provisions
- SECTION 5001 GENERAL
- SECTION 5003 GENERAL REQUIREMENTS
- SECTION 5004 STORAGE
- SECTION 5005 USE, DISPENSING, AND HANDLING, and
Chapter 54: Corrosive Materials
- SECTION 5401 GENERAL
- SECTION 5403 GENERAL REQUIREMENTS
- SECTION 5404 STORAGE
- SECTION 5405 USE
In Chapter 54, we see right off the bat that NH3 gas will also have to meet Chapter 53: Compressed Gases, which I have already explained those requirements in other postings. In this posting, I want to cover those items that are SPECIFIC to NH3.
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5403.1 Quantities not exceeding the maximum allowable quantity per control area. The storage and use of corrosive materials in amounts not exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Sections 5001, 5003, and 5401. |
The stored quantities per control area are addressed in Section 5001 if the quantities do not exceed the amounts in Table 5003.1.1(2) or 5003.1.1(4).
The tables address quantities posing a health hazard for control areas located indoors and outdoors.
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5403.2 Quantities exceeding the maximum allowable quantity per control area. The storage and use of corrosive materials in amounts exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with this chapter and Chapter 50. |
Tables 5003.1.1(2) and 5003.1.1(4) give the maximum allowable quantity per control area (MAQ).
If the amounts exceed the allowable quantities, the occupancy classifications in Chapter 2 and this chapter must be used for requirements.
Section 5003.1.4 states that compliance with Chapter 50 is also required.
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5404.1 Indoor storage. Indoor storage of corrosive materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(2), shall be in accordance with Sections 5001, 5003, and 5004 and this chapter. |
Table 5003.1.1(2) gives the maximum quantities for an indoor storage control area. Section 5004 addresses the storage requirements of hazardous materials in amounts that exceed the MAQ.
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5404.2 Outdoor storage. Outdoor storage of corrosive materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(4) shall be in accordance with Sections 5001, 5003, and 5004 and this chapter. |
Table 5003.1.1(4) gives the maximum quantities for an outdoor storage control area. Section 5004 addresses the storage of hazardous materials in amounts that exceed the MAQ.
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5404.2.2 Distance from storage to exposures. Outdoor storage of corrosive materials shall not be within 20 feet (6096 mm) of buildings not associated with the manufacturing or distribution of such materials, lot lines, public streets, public alleys, public ways, or means of egress. A 2-hour fire barrier without openings or penetrations and extending not less than 30 inches (762 mm) above and to the sides of the storage area is allowed in lieu of such distance. The wall shall either be an independent structure or the exterior wall of the building adjacent to the storage area. |
The required separation distances for corrosive materials are intended to reduce the hazard of radiant heat transfer from nearby exposures on or off the property.
This section also recognizes that a 2-hour fire barrier constructed in accordance with Section 707 of the International Building Code® (IBC®) will provide physical barrier protection as an alternative to the required separation distance. Note that the wall must be positioned to restrict the spread of fire around or over it.
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5405.1 Indoor use. The indoor use of corrosive materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(2) shall be in accordance with Sections 5001, 5003, and 5005 and this chapter. |
Table 5003.1.1(2) gives the MAQ for use in either a closed system or an open system.
Section 5005 addresses the use, dispensing, and handling of hazardous materials in amounts that exceed the MAQ.
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5405.1.2 Ventilation. Where corrosive materials are dispensed or used, mechanical exhaust ventilation in accordance with 5005.2.1.1 Ventilation “Where gases, liquids or solids having a hazard ranking of 3 or 4 in accordance with NFPA 704 are dispensed or used, mechanical exhaust ventilation shall be provided to capture gases, fumes, mists or vapors at the point of generation. Exception: Gases, liquids or solids that can be demonstrated not to create harmful gases, fumes, mists or vapors.” Section 5005.2.1.1 shall be provided. |
This section requires mechanical exhaust ventilation for all storage areas containing corrosive liquids with positive vapor pressures, which, if exposed under standard room temperature and atmospheric pressure, give off hazardous fumes and vapors. Adequate mechanical ventilation will reduce the chance for the accumulation of hazardous concentrations of toxic fumes and vapors. Corrosive liquids without a positive vapor pressure do not readily give off vapors at hazardous concentration levels under normal conditions and, therefore, do not require mechanical exhaust ventilation.
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5405.2 Outdoor use. The outdoor use of corrosive materials in amounts exceeding the maximum allowable quantity per control area indicated in Table 5003.1.1(4) shall be in accordance with Sections 5001, 5003, and 5005 and this chapter. |
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5405.2.1 Distance from use to exposures. Outdoor use of corrosive materials shall be located in accordance with Section 5404.2.2. |