Office in Rotorua Energy Events Centre closed over unsafe levels of hydrogen sulphide

The office at Rotorua's Energy Events Centre is being monitored daily and the council’s property team is checking gas levels on a “regular basis”. Photo / Andrew Warner

An office within Rotorua’s Energy Events Centre has closed after “unsafe levels” of a toxic gas were detected.

An agenda item for this week’s Rotorua Lakes Council infrastructure and environment committee meeting detailed how levels of hydrogen sulphide “rose significantly” in the sales and finance office recently.

The area was closed due to “unsafe levels”, and an investigation was to begin to identify and provide longer-term remediation.

The council provided more details after questions from Local Democracy Reporting.

“A staff member detected and reported an unusual odour in an office and promptly reported it.”

A facilities manager then used a calibrated gas monitor to investigate and found an initial hydrogen sulphide reading of 30.6 parts per million (ppm) near the staff member’s desk.

“Subsequent tests showed levels fluctuating between 0-5 ppm, well below the serious harm threshold of 250-500 ppm,” a spokesperson said.

The incident did not meet the criteria for reporting it to WorkSafe, as it was addressed promptly upon reporting by staff.

“Recent tests have shown safe levels and, as a precaution, the office will remain closed until [the] potential cause has been identified.”

The building was monitored daily and the council’s property team monitored gas on a “regular basis”.

Investigations were continuing to identify the possible source of the initial elevated reading.

WorkSafe’s website describes hydrogen sulphide as a highly toxic, colourless gas that occurs in a variety of natural and industrial settings, including geothermal ones.

The events centre is based at Sulphur Point, a geothermal hotspot.

Impacts of exposure vary according to concentration.

At low levels, hydrogen sulphide can irritate the eyes, nose and throat. Exposure to high levels may cause shortness of breath, lung damage or cardiac arrest.

At less than 1ppm, most people smell something similar to rotten eggs.

Between 20 and 150ppm, the nose and throat may feel dry and irritated. Eyes sting, itch or water, and “gas eye” symptoms (similar to mild conjunctivitis) may occur. Prolonged exposure may cause coughing, hoarseness, shortness of breath and a runny nose.

Levels above 100ppm are “immediately dangerous to life and health”.

Levels above 500ppm cause immediate loss of consciousness. “Death is rapid, sometimes immediate.”

WorkSafe confirmed it had not been notified.

Laura Smith is a Local Democracy Reporting journalist based at the Rotorua Daily Post. She previously reported general news for the Otago Daily Times and Southland Express, and has been a journalist since 2019.

- LDR is local body journalism co-funded by RNZ and NZ On Air.