Reparations of $13,500 were awarded to one victim, and $3500 to another
Their investigation found there were shortcomings including failure to adequately secure a valve on the calibrating unit.
None of the companies involved had managed the health and safety of their own or other workers on site that day, WorkSafe said.
Energy and Public Safety head of high hazards Tony Hetherington said there was a "high potential for death or serious harm if ignition occurred".
"This was an incident that had the potential for loss of life and serious injury. If the gas had ignited there would have also been significant damage to the plant and equipment at the site.
"These failings were concerning from a health and safety viewpoint, but also illustrate how good safety management safeguards the ability of the business to maintain operations."
The companies should have sufficient systems in place to prevent such an incident, especially with the potential "for a major incident" with a flammable substance.