About 90 workers were evacuated from the Woolworths Distribution Centre at Warnervale last week when the alarm was raised over a gas leak.
Multiple emergency services crews raced to the centre at about 10.30pm on Wednesday, December 14 when the alarm activated indicating an ammonia leak.
Anhydrous ammonia is a colourless gas that has a strong smell and is toxic, corrosive and flammable and serves as an industrial refrigerant gas.
Crews spent the next several hours locating the source of the leak and with the assistance of a technician from Sydney, the problem was located in a chilling room.
A spokesperson for Woolworths said the alarm was activated in error due to a faulty sensor and that there were no system leaks detected.
Rural Fire Services from Hamlyn Terrace and Berkeley Vale, along with the Duty Commander Central Coast, Police and Ambulance crews remained on scene until the site was declared safe for workers to return.
Sue Murray