The IIAR has released a proposed draft of IIAR 2 Safety Standard for Design of Closed-Circuit Ammonia Refrigeration Systems for public review. Here’s the notice:

March 20th, 2020


IIAR Members


First (1st) Public Review of Standard BSR/IIAR 2-202x, Safety Standard for Design of Closed-Circuit Ammonia Refrigeration Systems.

A first (1st) public review of draft standard BSR/IIAR 2-202x, Safety Standard for Design of Closed-Circuit Ammonia Refrigeration Systems is now open. The International Institute of Ammonia Refrigeration (IIAR) invites you to make comments on the draft standard. Substantive changes resulting from this public review will also be provided for comment in a future public review if necessary.

BSR/IIAR 2-202x specifies the minimum safety criteria for design of closed-circuit ammonia refrigeration systems. It presupposes that the persons who use the document have a working knowledge of the functionality of ammonia refrigerating system(s) and basic ammonia refrigerating practices and principles. This standard is intended for those who develop, define, implement and/or review the design of ammonia refrigeration systems. This standard shall apply only to closed-circuit refrigeration systems utilizing ammonia as the refrigerant. It is not intended to supplant existing safety codes (e.g., model mechanical or fire codes) where provisions in these may take precedence.

IIAR has designated the revised standard as BSR/IIAR 2-202x. Upon approval by the ANSI Board of Standards Review, the standard will receive a different name that reflects this approval date.

We invite you to participate in the first (1st) public review of BSR/IIAR 2-202x. IIAR will use the American National Standards Institute (ANSI) procedures to develop evidence of consensus among affected parties. ANSI’s role in the revision process is to establish and enforce standards of openness, balance, due process and harmonization with other American and International Standards. IIAR is the ANSI-accredited standards developer for BSR/IIAR 2-202x, and is responsible for the technical content of the standard.

This site includes links to the following attachments:

The 45-day public review period will be from March 20th, 2020 to May 4th, 2020. Comments are due no later than May 4th, 2020.

Thank you for your interest in the public review of BSR/IIAR 2-202x, Safety Standard for Design of Closed-Circuit Ammonia Refrigeration Systems.

There are MANY proposed changes. I’ll include a full list of the proposed changes at the end of the post, but here are some highlights:

  • Requirements for System Signage became a little simpler
  • Ammonia detection requirements have changed
    • Most installations now need two detectors in a machine room
    • Installation & Testing for detectors outside machine rooms now refer to external RAGAGEPs.
    • “Level 1” detection now requires liquid & hot gas shutoff at 150ppm
    • Requires AHJ approval if not installing ammonia detection in “Areas Other than Machinery Rooms”
  • New requirements for permanently installed Hoses and Corrugated Metal Fittings to ensure they meet ISO 10380 or ARPM IP-14


It’s important that YOU read these changes and make your voice heard if you have any input on them. 


Full change list of the normative sections of the standard below…

Ch 1: Replacement of “Replacement of machinery, equipment, or piping with functional equivalents” to “in-kind replacement”


Ch 2: Added two definitions

pumpout: The removal of ammonia from the system or a portion of the system to a level of evacuation suitable for the safe servicing of the system or portion of the system.

regularly patrolled: a documented frequency of inspection as determined by hazard analysis.


Ch 4: Location of Ammonia Refrigeration Machinery

4.2.2 Added new requirements for Outdoor Installations to meet sections 7.2.5 Temperature Control Ventilation, 7.2.8 Service Provisions, 7.2.11 Eyewash Safety Showers, and 7.3.2 Natural / Mechanical Ventilation.

4.2.3(1) Evaporators becomes “Low-side evaporators and associated surge drums (if applicable)”

4.2.3(2) “Condensers used for heating the space in which they are located” becomes “Heat exchangers used for heating a space in which they are located or for warming a process fluid”

4.2.3(4) “Valves, including but not limited to control and pressure-relief valves, and connecting piping, any of which are associated with Items 1, 2, and 3” becomes “Piping, including but not limited to control and pressure-relief valves”


Ch 5: General System Design Requirements Limited Charge Systems section on allowing the Limited Charge System to be rated at the set-pressure of the relief device is removed. Connecting to Existing Low-Pressure Equipment. Changed the allowable low-side pressure from matching “existing” rating to requiring it be a minimum of 250PSIG.

5.5.4 New requirement: “Abnormal Pressure or Shock Mitigation. Piping systems shall be designed to mitigate Protection against abnormal pressure or shock shall be provided for equipment and piping sections that are subject to any of the following mechanisms:

  1. Sudden Liquid Deceleration
  2. Vapor-Propelled Liquid Slug
  3. Condensation-Induced Shock

5.12 Service Provisions becomes Service and Accessibility Provisions

5.12.3 Removes “Provisions for functional testing shall not require disassembly of ammonia-containing portions of the system” from “Maintenance and Function Testing” section.

5.12.5 Access to Valves  (New Section – previously in 6.3.3) *Manually operated valves that are inaccessible from floor level shall be operable from portable platforms, fixed platforms, ladders, or shall be chain operated. Manually operated isolation valves identified as being part of the system emergency shutdown procedure shall be directly operable from the floor or chain operated from a permanent work surface. Emergency valve identification shall comply with Section 5.14.4. New requirement that non-listed or ASME B&PVC pressure-containing equipment is “proof tested”

5.14.1 Machinery Room signage requirements used to be referenced to section 6.15. This new section called “System Signage” brings older requirements to this section. You may be familiar with this sign as we used to call it the “contractor” sign under ASHRAE 15.

Signage or schematic drawings shall be posted at a location that is readily assessible to trained refrigeration staff and trained emergency responders. Schematic drawings or signage shall include the following information:

    1. Instructions with details and steps for shutting down the system in an emergency
    2. The contact information for whom to contact in an emergency
    3. Quantity of ammonia in the system
    4. Type and quantity of refrigerant oil in the system
    5. Field test pressures applied.

(Note that #2 above replaces the old text “The name and telephone numbers of the refrigeration operating, maintenance, and management staff; emergency responders; and safety personnel. The names and telephone numbers of all corporate, local, state, and federal agencies to be contacted as required in the event of a reportable incident.”)

5.14.3 Machinery Labels becomes “Equipment Labels” Adds reference to (Section ASME B&PVC, Section VIII, Division 1) UG-120

5.15.2 Egress becomes Access: “Operational and maintenance service access shall be provided by access panels or doors, or the design shall provide for removal of equipment to a remote location for service and subsequent reinstallation.”

5.15.3 (NEW) * Ammonia Detection and Interlocks. Enclosures that have the potential to reach a concentration of 40,000 ppm from a refrigerant release from the largest independent circuit within the enclosure and have either 1) open flames or hot surfaces as described in Section 6.5 or 2) have unclassified electrical equipment, shall be provided with ammonia detection and interlocks that will disable the ignition source(s) at or below a concentration of 40,000 ppm.

5.16.1 Protection. Adds the word “equipment” and allows the use of administrative controls to the list of approved protection measures.

5.16.7 Refrigerant Piping. Removes “caution signs” as an acceptable control for “piping having an external surface temperature of 140°F (60°C) or higher and located outside the machinery room at a height less than 7.25 ft (2.2 m) above the floor, or located adjacent to passageways, aisles, walkover stairs, or landings”


Ch 6: Machinery Rooms

6.5 Open Flames and Hot Sources, Exception #3. Added “or when ammonia concentration is equal to or greater than 40,000 ppm” to list of prohibited conditions for use of matches, lighters, sulfur sticks, welding equipment, etc.

6.7 Eyewash/Safety Shower. This section is revised to

1) Clarify that the eyewash station outside the machine room must be within 55’ of the machinery room door

2) Provide an exception (which I truly hope NOBODY ever attempts to use) to the Eyewash/Safety Shower requirement in certain circumstances

6.10.3 Clarifies that the prohibition on exit doors underneath stairways does not apply unless the stairway is a designated as an emergency egress

6.12.1 Emergency Stop Switch. Removed the requirement for a “tamper resistant cover” but states that the “switch shall be protected from inadvertent operation.”

6.13 Ammonia Detection and Alarm (Revisions)

6.13.1 Now requires TWO NH3 detectors. (Exception: The use of a single detector is permitted if the detector has a Safety Integrity Level (SIL) 2 or SIL 3 rating.)

6.13.1(1) Sensors must have identical concentration ranges

6.13.1(2) Detectors must be tested and marked in accordance with FM 6320 “Combustible Gas Detectors” or UL 2075 “Standard for Safety: Gas and Vapor Detectors and Sensors” (Combined previous requirements in one location) *Detection of ammonia concentrations equal to or exceeding 25 ppm shall activate visual indicators, and audible alarms, and provide a notice to a monitored location. Previous text “Once activated, emergency ventilation shall continue to operate until manually reset by a switch located in the machinery room” now reads “Once activated, emergency ventilation, visual indicators, and audible alarms shall continue to operate until manually reset by a switch located in the machinery room.” Adds “and shall remain de-energized until being manually reset” to 40,000ppm shutdown requirements. Adds an exception for some room doors and roof hatches within 20’ of exhaust: “EXCEPTION: Machinery room exhaust is permitted to be installed within 20 ft. (6m) of tight-fitting machinery room doors and roof hatches that are not designated for emergency egress and that have signage indicating they must be closed after passage.” Clarified that requirement for 2,500 ft/min velocity only applies to emergency exhaust. Clarified non-sparking blades requirement: “Where the function of machinery room fans is intended to exhaust ammonia, such fans shall be equipped with spark-resistant blades.” Allows smaller than ¼ inch mesh screens under certain circumstances. Clarified that fail-open type requirement only applies to motorized louvers or dampers that are used for emergency ventilation systems

6.14.7 This section is still under construction and reviewers were asked not to comment on it. The Testing requirements were removed because they are now in IIAR 6.

6.15.5 A new “Electric Hazard” sign is required for Hazardous (Classified) Locations.


Ch 7: Refrigeration Equipment Located in Areas Other than Machinery Rooms

7.2.1 Separation requirements have added “in accordance with the building code” before “tight construction with tight-fitting doors”

7.2.3 Exceptions clarified:

  1. Unoccupied areas with continuous piping that has been joined by welding and does not include valves, valve assemblies, equipment, or equipment connections.
  2. Where approved by the AHJ, rooms or areas in industrial occupancies that are normally occupied 24 hours/day and are regularly patrolled when the room’s function is idled for scheduled downtime and are provided with an alternative to fixed detection and alarm equipment, such as an emergency action plan. A means for emergency notification shall be provided.

7.2.5 Clarified to show that Temperature Control Ventilation is only required for areas not refrigerated or air conditioned.

7.2.9 Clarified that only Penthouses that are automatically isolated from the interior space are to be treated as equipment enclosures.

7.2.11 (NEW) *Eyewash/Safety Shower. A permanent or portable means for the provision of quick drenching or flushing of the eyes and body within or directly adjacent to the work area for immediate emergency use when maintenance occurs that involves the deliberate opening of an ammonia refrigeration system. Such means shall be indicated in the design documents, and shall comply with the temperature, flow and duration specifications of ANSI/ISEA Z358.1.

7.3.3 Clarified that ventilation for Equipment Pits Located Indoors must meet and requirements in addition to and


Ch8: Compressors Clarified that when choosing the relief valve scenario “The condition that requires the larger relief valve selection shall be used.” Clarified that “The minimum size compressor pressure relief connection shall be a ½” fitting or ¾” pipe and shall be in accordance with Section 15.4.2.”


Ch10: Condensers

10.1 General: Condensers shall be designed and constructed in accordance with ASME B31.5 or ASME Boiler and Pressure Vessel Code.


Ch11: Evaporators

11.1 General: Evaporators shall be designed and constructed in accordance with ASME B31.5 or ASME Boiler and Pressure Vessel Code.

(New) Fluid Freeze Protection. When heat exchangers are used to cool products or secondary coolants that are not intended to be frozen, the system shall be designed to prevent damage from freezing within the heat exchanger.

(New) Frozen Products. Evaporators or heat exchangers intended to freeze products by direct contact with the heat exchanger shall be designed to accommodate the frozen product without damaging the heat exchanger or associated refrigerant -containing equipment. Drain Lines freezing protection simplified to “A means for preventing freezing inside condensate drain line shall be provided where lines are exposed to freezing temperatures.” Air migration prevention simplified to “means shall be provided to prevent warm air from migrating through the condensate drain piping to the condensate drain pan connections”

12.5.2 Nameplate Mounting. Added “Alternatively, it is permitted to use a duplicate nameplate in accordance with section When duplicate nameplates are used, the original nameplates must be affixed to the vessel.”


Ch 13: Piping

Section renamed to “Piping, Valves and Hoses”

(NEW) *Hoses and Corrugated Metal Fittings. Hoses and corrugated metal fittings used within closed-circuit refrigeration systems shall be designed for permanent installation and meet or exceed the pressure, marking, and manufacturing requirements of ISO 10380 or ARPM IP-14.

13.3.1 Required Shut-Off Valve Locations. Item #3 removed the word “liquid” so it now reads “At the refrigerant inlet and outlet of a pressure vessel containing ammonia and having an internal gross volume exceeding 3 ft3 (0.085 m3).” (NEW) *Shut-off valves connecting ammonia-containing equipment or piping to atmosphere shall have a maximum operating pressure differential (MOPD) or a maximum seat sealing pressure differential (MSSPD) equal to or greater than the system design pressure.

13.5.1 Added “Any projection from the ceiling over a means of egress shall not reach a point less than 6 ft.-8 in. (2.0 m) from the floor” to the 7.25’ height exception.


Ch15: Overpressure Protection Devices

15.1.3 (Modified) *Rupture discs are not permitted as the only means of pressure relief to atmosphere. They are permitted to be used in series with atmospheric pressure relief valves and in accordance with Section 15.2.7. Rupture discs are permitted as a sole means of overpressure protection for equipment only where the outlet of the rupture disc is into another part of a pressure-protected system. Rupture discs used in these applications shall be fitted with a tell-tale device that will provide a visual indication that the disc has burst.

15.2.5 Modified the exception to read “EXCEPTION: The vapor relief connection on an oil drain pot and similar applications shall be located at the highest point on the vessel.” Modified to read “Pressure relief devices shall be marked by the manufacturer with the data required in ASME B&PVC, Section VIII, Division 1. Calibration and set pressure adjustments to pressure relief devices shall be performed by the relief device manufacturer or a company holding a certification for this work, who shall seal the valve.”

15.3.6(1) & (2) Clarified that all the conditions need to be met. Clarified intent so “This relief capacity protection includes heat loads from cleaning operations and process loads” becomes “Engineering controls other than pressure relief devices are permitted to prevent or relieve overpressure due to internal loads.” Changed “considered” to “analyzed” and added “When internal heat loads exceed the fire case external heat load, the equipment may be protected either by increasing the size of the pressure relief device, or by a combination of a pressure relief device sized for the fire case heat load and engineering controls which mitigate the risk of the internal heat load exceeding the fire case heat load.”

15.3.9 Clarified intent so “a pressure vessel” now reads “equipment that is protected with vapor pressure relief devices.” This may require additional relief scenarios where combustible materials are stored / installed within 20’.

15.4.1 Clarified intent “*Stop valves shall not be installed in the inlet piping of pressure relief devices. Where installed in the outlet piping of pressure relief devices, the pressure drop effects of full area stop valves shall be taken into account in the engineering of the relief vent piping system. Where used, any stop valve installed in relief outlet piping shall be locked open. This includes both stop valves installed in the outlet of two relief valves mounted on a dual manifold, regardless of the position of the three way valve. When stop valves installed in downstream piping of a relief device are closed, a parallel relief valve shall be provided, or the protected part of the system shall have the ammonia removed and opened to atmosphere.

15.4.3 Added “Stainless steel tubing with nominal diameter of 1 ½” through 8”, shall have a minimum thickness of 16 gage (0.065 inch) and shall be connected by welded fittings.”

15.4.3 Exception #2 Clarified that malleable iron ASTM A197 fittings are permitted for atmospheric discharge relief piping.

Equation Removed ASHRAE 15 reference, Clarified terms in the equation & Removed “that is occupied solely during service and inspection.”

15.5.4 (NEW) “*Where required by the AHJ, refrigeration systems that require a machinery room per Section 4.2 shall be evaluated to determine whether direct atmospheric release of ammonia from relief valves would create a public health risk. If a public health risk is determined to exist, either an emergency pressure control system (EPCS) or one of the exceptions listed in Section 15.5.1 shall be provided.” Note: 15.5.1 exceptions include treatment systems, flare, diffusion, etc.

15.5.3 (NEW Requirement) Added “Where multiple relief devices are used on a single piece of equipment to provide the required capacity while operating in parallel, the combined capacity shall be used to determine the size of the diffusion tank. Liquid ammonia shall not be directed to the diffusion tank.” Also changed the word “considered” to “reflected” concerning the effect of backpressure due to static head of the water in the tank. (NEW) “Relief valves used for hydrostatic protection of a vessel constructed in accordance with the ASME B&PV code are required to be constructed and marked in accordance with the ASME B&PV Code.”

15.6.4 (NEW) *Use of Shut-off Valves. Full area shut-off valves are permitted on hydrostatic relief systems if installed in accordance with this section. When shut-off valves are installed, administrative controls shall be engaged to prevent hydrostatic over-pressure. (NEW) Full area shut-off valves are permitted on the inlets and outlets of hydrostatic pressure relief valves for the purpose of inspection, testing, and repair of the pressure relief valve. (NEW) Shut-off valves are not permitted on the inlet of ASME hydrostatic relief valves that are required per section


Ch 17: Ammonia Detection and Alarms

17.1 Scope – Added “Ammonia detectors and notifications designed and installed in accordance with this chapter are to serve as a signal of a potentially hazardous condition that requires investigation and evaluation by a designated person(s).”

17.2 Power for Detectors and Alarms renamed to “Installation Design Requirements” with several new items:

17.2.1 Power Supply – Replaced “Dedicated Branch Circuit” with “be supplied by an electrical feeder separate from those supplying power to other refrigeration equipment and controls.”

17.2.2 Wire Runs – (NEW) Detectors shall use supervised wire runs such that any faults in the wiring are reported to a monitored location.

17.2.3 Communication – (NEW) Loss of communication between the detector and the control system(s) that enables response shall be reported to a monitored location.

17.2.4 Monitoring Sensing Elements – (NEW) Detectors shall actively monitor the primary sensing element(s) and report any trouble signal to a monitored location.

17.3.1 Testing renamed to “Design Standards”

17.3.1 (NEW) In Indoor Areas other than a Machinery Room. Ammonia detectors installed in indoor areas other than machinery rooms shall be designed and tested in accordance with UL-61010-1 “Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use” or ANSI/ISA 92.00.01 “Performance requirements for Toxic Gas Detectors”

17.3.2 (NEW) In Machinery Rooms. Ammonia detectors installed in machinery rooms shall meet the design and marking requirements per Section 6.13.1

17.4 Detector Placement – Reworded to read “A leak detection sensor, or the inlet of a sampling tube that draws air to a leak detection sensor, shall be mounted in a position where it is expected to be the most effective. Leak detection sensors and sampling tube inlets shall be positioned where they can be accessed for maintenance and testing.”

17.7.1(3) Level 1 Ammonia Detection and Alarm – (NEW) Upon detection of a concentration of 150 ppm or higher, control valves feeding liquid and hot gas to equipment in the affected area shall be closed.

17.7.2(3) Level 3 Ammonia Detection and Alarm – Reworded to “Audible and visual alarms shall be provided inside the room to warn that, when the alarm has activated, access to the room is restricted to personnel authorized to respond to alarms and emergency responders.”