IIAR 2-2021: Ammonia Detection Requirements
With the recent publication of ANSI/IIAR 2-2021, it seemed appropriate to post a blog summarizing the minimum ammonia detection requirements for new ammonia refrigeration systems.
Machinery Rooms
Ammonia detection inside machinery rooms is addressed in §6.13. At minimum, machinery room ammonia detection must include:
- At least two detectors with identical sensing ranges must be installed. A single detector is permitted if a failure of the detector activates the emergency ventilation system and de-energizes refrigeration machinery inside the room.
- Audible and visual alarms must be installed inside the room and outside each entrance to the room to warn that access to the room is restricted when the alarm is activated.
- Detection of 25 ppm must activate audible alarms, visual alarms, and provide notification to a monitored location. The audible and visual alarms can be automatically reset if the concentration drops below 25 ppm.
- Detection of 150 ppm must activate audible alarms, visual alarms, and emergency ventilation. Emergency ventilation must remain activated until manually reset by a switch inside the machinery room. Audible and visual alarms must remain activated until manually reset by a switch inside the machinery room or alternatively in an area remote from the machinery room.
- Detection of 40,000 ppm or the detector’s upper limit must activate visual alarms, audible alarms, emergency ventilation, and de-energize compressors, pumps, and normally closed automatic valves. Emergency ventilation must remain activated until manually reset by a switch inside the machinery room. Audible and visual alarms must remain activated until manually reset by a switch inside the machinery room or alternatively in an area remote from the machinery room.
- If the machinery room houses fuel burning equipment with open flames or surfaces exceeding 800ºF, the equipment must be interlocked with the detector to shut off if the concentration reaches 40,000 ppm or the detector’s upper limit.
Other Than Machinery Rooms
Where ammonia-containing equipment is located inside, but not in a machinery room (other than machinery room), the detection system must include:
- In general, “other than machinery rooms” require Level 1 detection. Level 1 detection demands at least one detector in the room which activates an alarm that reports to a monitored location if the concentration reaches 25 ppm.
- Detection is not required in unoccupied areas with continuous welded pipes that do not include valves or equipment.
- Where allowed by the AHJ (Authority Having Jurisdiction), rooms that are occupied 24/7 and are regularly patrolled do not require detection.
- Where allowed by the AHJ, alternatives to fixed detection is allowed in rooms where harsh conditions are incompatible with detection devices.
- Where a room is required to have emergency ventilation per §7.3.1 Level 3 detection must be provided. Level 3 detection calls for the following:
- At least one detector in the room.
- Audible and visual alarms must be installed inside the room to warn that access to the room is restricted when the alarm is activated.
- Detection of 25 ppm must activate audible alarms, visual alarms, provide notification to a monitored location, and close solenoid control valves feeding liquid and hot gas to equipment. Any refrigerant pumps, non-emergency fans, or other motors that are part of the refrigeration system must also be de-energized.
Enclosures
Ammonia-containing enclosures that have the potential to reach 40,000 ppm must be equipped with ammonia detection to de-energize equipment and disable ignition sources if the enclosure houses electrical equipment or fuel burning equipment.
Packaged systems
Where ammonia is the refrigerant within a packaged system, the following detection requirements apply:
- Packaged systems located inside a machinery room must comply with the machinery room detection requirements.
- Packaged systems located inside an “other than machinery room” must comply with the requirements of that section.
- Packaged systems located outdoors with a free-aperture area exceeding F = G0.5 [where F = free opening area (ft2) and G = mass of ammonia in the system (lb)], do not require ammonia detection. If the free-aperture area does not exceed F = G0.5, ammonia detection is required.
Other Requirements
- A means for monitoring ammonia concentration during a power failure must be available. Typically, this is accomplished using a hand held detector.
- The detection system must be powered independently of the emergency controls. If the e-stop is activated, the ammonia detection must continue to operate.
- If power is lost to the ammonia detection system, a signal must be sent to a monitored location.
- All detectors must be placed in a location where they are expected to be the most effective and positioned to be accessed for maintenance and testing.
- Detection alarms must provide a sound pressure of 15 dBA above average ambient sound level and 5 dBA about the maximum sound level.
- Detection alarms must be accompanied by signage explaining the meaning of the alarm.
One of my customers has a chiller system for an ice arena. They have NH3 leak detection for chiller room only. They have had apartments built up around them. Should I recommend a vent line sensor?
Thank you
If the relief valves discharge to atmosphere (not a diffusion tank with water), then a vent line sensor for this situation would be a great idea.
If we have a package system that we tied in new compressors due to reliability and we put a Lean to style roof over it does it require detection? The compressors did come out of an old engine room but they will be on pads in the free air.
No. Ammonia detection is not required for outdoor installations.
If a facility has a non-machinery room that encloses chillers and DOES exceed 100 connected compressor horse power, do ventilation requirements apply from IIAR 2-2021 7.3.l?
Without knowing all of the details, my answer is ‘No’. Detection per §7.3.1 would not be required because §7.3.1 only applies to non-machinery rooms with components that are not permitted in accordance with §4.2.3. §4.2.3 permits the following to be installed in non-machinery room industrial occupancies: 1) heat exchangers and associated surge drums; 2) low-probability pumps; 3) piping; and 4) systems with total connect power < 100 HP. Per §4.2.3 and §7.3.1, chillers (heat exchangers) can be installed in non-machinery rooms and no special ventilation is required.
Do you need to have the Emergency stop tied in with an audio and visual alarms? If so, are there any specification we need to adhere by?
No. There is no prescriptive requirement in IIAR 2 or 9 that the e-stop be interlocked with the audible and visual alarms. If you choose to interlock the e-stop with the alarms, you could choose the sound/light alarm levels.