11 In the context of this case, 30 second exposure values corresponding to the AEGL 1, AEGL2 and AEGL3 values are as follows:
- 30 seconds, AEGL1, 134 ppm, non-disabling effects
- 30 seconds, AEGL2, 984 ppm, disabling effects
- 30 seconds, AEGL3, 12,075 ppm, lethal effects
Length of ammonia exposure
12 The length of time that Mr Hutt was exposed to ammonia gas would be regarded as acute rather than chronic.
Effects of Ammonia exposure on Mr Hutt
13 It is improbable that a length of exposure of less than 30 seconds would lead to long lasting effects to Mr Hutt such as effects associated with repeated exposure, ie, chronic irrigation of the eye and note [sic], chronic dyspnea, cough and obliterate bronchiolitis.
MATTERS RELATED TO REFRIGERATION ENGINEERING
14 As referred to at [48] of the Statement of Agreed Facts, the cause or causes of the Incident included:
a. a nut used to secure one of eight bolts on a flange joint located on a discharge pipe was not attached to that bolt at the time of the Incident; and
b. a gasket used to secure that flange joint located on a discharge pipe failed. When the flange joint was opened after the Incident, it was observed that the gasket was brittle, a section of the gasket was missing, the gasket appeared to have been used or compressed several times as indicated by markings on the seal face and by reduced sectional thickness.
15 Reuse and the brittleness of the gasket was a contributing factor. The reuse or recompression of the gasket should not have occurred. Standard practice would be to replace gaskets if the joint had been opened up, at major service intervals and or 25,000 hour overhauls.
16 Most industrial facilities rely on third party contractors to maintain and service their ammonia refrigeration plants.
17 It is common for the refrigeration contractor to propose maintenance contract scope and terms.
18 Regular monthly maintenance is common. Maintenance contractors would identify additional works to be undertaken as additional works.
19 Visual inspection and leak detection (via odours) of flange joints in ammonia refrigeration plants is standard practice.
20 The overall maintenance regime and frequency in place at the Premises was appropriate providing it was being performed properly.
21 Checking tightness of the bolts may have prevented the incident, however, checking tightness of bolts is not normal industry practice.