RAGAGEP: Historical Variants and the Importance of IIAR Standards | Part 6: Ammonia Detection & Ventilation Control

March 8th, 2022 | , ,


Uriah Donaldson, OHST, presented a technical paper at the 2019 RETA National Conference and 2021 IIAR National Conference titled RAGAGEP: Historical Variants and the Importance of IIAR Standards.

This is the sixth post in a series of blogs which include excerpts from his technical paper.

Ammonia Detection

Requirements related to ammonia detection systems can be grouped into six (6) major categories: machinery rooms, audible/visual alarms, refrigerated spaces, ventilation control, emergency shut off, and testing.

Ammonia detection, above any other subject, may quite possibly be the most confusing and contradictory among the various RAGAGEP code and standard documents. Because of the vastness of this subject, this discussion will be limited to the historical RAGAGEP variants in a single category: Ventilation Control. For further study, a detailed chart showing the varying requirements of the major code and standard documents across the six categories is provided (here).

Ventilation Control

Surprising to some in the industry, the RAGAGEP precedent for both machinery room ammonia detection and automatic ventilation control has been around since the ANSI certified publication of IIAR 2 in the 1970s. Initially, IIAR 2 required that machinery rooms “shall be provided with an independent mechanical ventilation system actuated automatically by a vapor detector(s) when the concentration of ammonia in the room exceeds 40,000 parts per million.”[1] IIAR maintained its 40,000 PPM requirement until its third major revision in 1999, lowering its automatic ventilation activation level to 1,000 PPM. This was ostensibly to conform with ASHRAE 15 which initially required that machinery rooms “shall have continuous ventilation or be equipped with a vapor detector that will automatically start the ventilation system and actuate an alarm at the lowest practical detection levels…”[2] but later revised its standard in 1994 to 1,000 PPM.[3]

The year 2000 was an interesting RAGAGEP year for machinery room ventilation control. In its two previous publications (1994 & 1997) the Uniform Fire Code maintained a requirement for machinery room ventilation to be automatically activated at “50 percent of the IDLH”[4] (e.g. 150 PPM for ammonia) which conformed with the Uniform Mechanical Code.[5] In its 2000 revision, this requirement was dropped entirely by the UFC and later brought back in 2003 with a higher level of 1,000 PPM.[6]

Why NFPA 1 dropped its ventilation control requirement in 2000 is a mystery but setting the level at 1,000 PPM in its 2003 version is not. At that time, most of the other code and standard documents all required ventilation systems to be interlocked with ammonia detection and automatically activated at 1,000 PPM.[7] The lone exception to this was the Uniform Mechanical Code which maintained its requirement for ventilation to be activated at “50 percent of the IDLH”[8] until 2009 when it was updated to conform with all other code and standard documents by requiring, “purge fans shall also respond automatically to the refrigerant concentration detection system set to activate the ventilation system at no more than 1,000 parts per million.[9]

In 2010 IIAR 2-2008 Addendum A shook things up once again. While it maintained the 1,000 PPM requirement for activating emergency ventilation, it added a secondary requirement for activating normal ventilation at the Threshold Limit Value – Time Weighted Average (TLV-TWA e.g. 25 PPM for ammonia).[10] IIAR maintained this position until its revised publication in 2014 when it changed once again. This time IIAR made a full RAGAGEP circle and required that ventilation be activated at 150 PPM (½ the IDLH).[11] This is the same as the initial requirement of the Uniform Mechanical Code in 1994.

At the time of this paper’s publication, all major mechanical and fire codes reference IIAR 2 and therefore, new detection and ventilation systems will need to conform with the 150 PPM requirement.

[1] ANSI / IIAR 1974-78 §

[2] ASHRAE 15 1989 §10.14(h)

[3] ANSI/ASHRAE 15-1994 §8.14(h)

[4] 1997 UFC §6311.4 Emergency Control of Ventilation Systems

[5] 1997 UMC §1107.5 Emergency Control of the Ventilation Systems

[6] 2003 NFPA 1 §, §

[7] ANSI/ASHRAE 15-2001 §8.12(h); 2000 IMC §1106.3 Ammonia Room Ventilation; ANSI/IIAR 2-1999 §6.2.3 Equipment

[8] 2000 UMC §1108.5 Emergency Control of the Ventilation Systems

[9] 2009 UMC §1108.5 Emergency Control of the Ventilation Systems

[10] ANSI/IIAR 2008 Addendum A §

[11] ANSI/IIAR 2014 §

The previous blogs are available in the following links:

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